LAN8720A/LAN8720AI
Small Footprint RMII 10/100 Ethernet
Transceiver with HP Auto-MDIX Support
Highlights
Key Benefits
• Single-Chip Ethernet Physical Layer Transceiver
(PHY)
• Comprehensive flexPWR® Technology
- Flexible Power Management Architecture
- LVCMOS Variable I/O voltage range: +1.6V
to +3.6V
- Integrated 1.2V regulator
• HP Auto-MDIX support
• Miniature 24-pin QFN/SQFN lead-free RoHS
compliant packages (4 x 4mm).
• High-Performance 10/100 Ethernet Transceiver
- Compliant with IEEE802.3/802.3u (Fast
Ethernet)
- Compliant with ISO 802-3/IEEE 802.3
(10BASE-T)
- Loop-back modes
- Auto-negotiation
- Automatic polarity detection and correction
- Link status change wake-up detection
- Vendor specific register functions
- Supports the reduced pin count RMII interface
• Power and I/Os
- Various low power modes
- Integrated power-on reset circuit
- Two status LED outputs
- Latch-Up Performance Exceeds 150mA per
EIA/JESD 78, Class II
- May be used with a single 3.3V supply
• Additional Features
- Ability to use a low cost 25Mhz crystal for
reduced BOM
• Packaging
- 24-pin QFN/SQFN (4x4 mm) Lead-Free
RoHS Compliant package with RMII
• Environmental
- Extended commercial temperature range
(0°C to +85°C)
- Industrial temperature range version available (-40°C to +85°C)
Target Applications
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Set-Top Boxes
Networked Printers and Servers
Test Instrumentation
LAN on Motherboard
Embedded Telecom Applications
Video Record/Playback Systems
Cable Modems/Routers
DSL Modems/Routers
Digital Video Recorders
IP and Video Phones
Wireless Access Points
Digital Televisions
Digital Media Adapters/Servers
Gaming Consoles
POE Applications (Refer to Application Note
17.18)
2016 Microchip Technology Inc.
DS00002165B-page 1
LAN8720A/LAN8720AI
TO OUR VALUED CUSTOMERS
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You can determine the version of a data sheet by examining its literature number found on the bottom outside corner of any page.
The last character of the literature number is the version number, (e.g., DS30000000A is version A of document DS30000000).
Errata
An errata sheet, describing minor operational differences from the data sheet and recommended workarounds, may exist for current devices. As device/documentation issues become known to us, we will publish an errata sheet. The errata will specify the
revision of silicon and revision of document to which it applies.
To determine if an errata sheet exists for a particular device, please check with one of the following:
• Microchip’s Worldwide Web site; http://www.microchip.com
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When contacting a sales office, please specify which device, revision of silicon and data sheet (include -literature number) you are
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DS00002165B-page 2
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Table of Contents
1.0 Introduction ..................................................................................................................................................................................... 4
2.0 Pin Description and Configuration .................................................................................................................................................. 6
3.0 Functional Description .................................................................................................................................................................. 14
4.0 Register Descriptions .................................................................................................................................................................... 41
5.0 Operational Characteristics ........................................................................................................................................................... 52
6.0 Package Information ..................................................................................................................................................................... 66
7.0 Application Notes .......................................................................................................................................................................... 71
Appendix A: Data Sheet Revision History ........................................................................................................................................... 73
The Microchip Web Site ...................................................................................................................................................................... 74
Customer Change Notification Service ............................................................................................................................................... 74
Customer Support ............................................................................................................................................................................... 74
Product Identification System ............................................................................................................................................................. 75
2016 Microchip Technology Inc.
DS00002165B-page 3
LAN8720A/LAN8720AI
1.0
INTRODUCTION
1.1
General Terms and Conventions
The following is list of the general terms used throughout this document:
1.2
BYTE
8-bits
FIFO
First In First Out buffer; often used for elasticity buffer
MAC
Media Access Controller
RMII™
Reduced Media Independent InterfaceTM
N/A
Not Applicable
X
Indicates that a logic state is “don’t care” or undefined.
RESERVED
Refers to a reserved bit field or address. Unless otherwise
noted, reserved bits must always be zero for write operations. Unless otherwise noted, values are not guaranteed
when reading reserved bits. Unless otherwise noted, do
not read or write to reserved addresses.
SMI
Serial Management Interface
General Description
The LAN8720A/LAN8720Ai is a low-power 10BASE-T/100BASE-TX physical layer (PHY) transceiver with variable I/O
voltage that is compliant with the IEEE 802.3-2005 standards.
The LAN8720A/LAN8720Ai supports communication with an Ethernet MAC via a standard RMII interface. It contains a
full-duplex 10-BASE-T/100BASE-TX transceiver and supports 10Mbps (10BASE-T) and 100Mbps (100BASE-TX) operation. The LAN8720A/LAN8720Ai implements auto-negotiation to automatically determine the best possible speed and
duplex mode of operation. HP Auto-MDIX support allows the use of direct connect or cross-over LAN cables.
The LAN8720A/LAN8720Ai supports both IEEE 802.3-2005 compliant and vendor-specific register functions. However,
no register access is required for operation. The initial configuration may be selected via the configuration pins as
described in Section 3.7, "Configuration Straps," on page 29. Register-selectable configuration options may be used to
further define the functionality of the transceiver.
Per IEEE 802.3-2005 standards, all digital interface pins are tolerant to 3.6V. The device can be configured to operate
on a single 3.3V supply utilizing an integrated 3.3V to 1.2V linear regulator. The linear regulator may be optionally disabled, allowing usage of a high efficiency external regulator for lower system power dissipation.
The LAN8720A/LAN8720Ai is available in both extended commercial and industrial temperature range versions. A typical system application is shown in Figure 1-1.
DS00002165B-page 4
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
FIGURE 1-1:
SYSTEM BLOCK DIAGRAM
10/100
Ethernet
MAC
RMII
LAN8720A/
LAN8720Ai
Mode
MDI
Transformer
RJ45
LED
Crystal or
Clock
Oscillator
FIGURE 1-2:
MODE[0:2]
nRST
ARCHITECTURAL OVERVIEW
Mode Control
Reset Control
AutoNegotiation
100M TX
Logic
100M
Transmitter
HP Auto-MDIX
RXP/RXN
Transmitter
RMIISEL
SMI
TXD[0:1]
Management
Control
10M TX
Logic
10M
Transmitter
TXP/TXN
MDIX
Control
TXEN
XTAL1/CLKIN
PLL
XTAL2
RXER
CRS_DV
RMII Logic
RXD[0:1]
100M RX
Logic
DSP System:
Clock
Data Recovery
Equalizer
Analog-toDigital
100M PLL
Receiver
MDC
10M RX
Logic
MDIO
Squeltch
& Filters
Interrupt
Generator
nINT
LED1
LEDs
Central Bias
LED2
RBIAS
10M PLL
PHY Address
Latches
PHYAD0
LAN8720A/LAN8720Ai
2016 Microchip Technology Inc.
DS00002165B-page 5
LAN8720A/LAN8720AI
2.0
PIN DESCRIPTION AND CONFIGURATION
FIGURE 2-1:
24-QFN/SQFN PIN ASSIGNMENTS (TOP VIEW)
VDD1A
19
TXN
20
LAN8720A/LAN8720Ai
12
MDIO
11
CRS_DV/MODE2
10
RXER/PHYAD0
(TOP VIEW)
TXP
21
RXN
22
9
VDDIO
RXP
23
8
RXD0/MODE0
RBIAS
24
7
RXD1/MODE1
VSS
NOTE: Exposed pad (VSS) on bottom of package must be connected to ground
Note 2-1
When a lower case “n” is used at the beginning of the signal name, it indicates that the signal is
active low. For example, nRST indicates that the reset signal is active low.
Note 2-2
The buffer type for each signal is indicated in the BUFFER TYPE column. A description of the buffer
types is provided in Section 2.2.
DS00002165B-page 6
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 2-1:
RMII SIGNALS
Num Pins
Name
Symbol
Buffer
Type
1
Transmit
Data 0
TXD0
VIS
The MAC transmits data to the transceiver using
this signal.
1
Transmit
Data 1
TXD1
VIS
The MAC transmits data to the transceiver using
this signal.
1
Transmit
Enable
TXEN
VIS
(PD)
Indicates that valid transmission data is present
on TXD[1:0].
1
Receive
Data 0
RXD0
VO8
Bit 0 of the 2 data bits that are sent by the transceiver on the receive path.
PHY Operating Mode 0
Configuration
Strap
MODE0
VIS
(PU)
Combined with MODE1 and MODE2, this configuration strap sets the default PHY mode.
Description
See Note 2-3 for more information on configuration straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 30 for
additional details.
1
Receive
Data 1
RXD1
VO8
Bit 1 of the 2 data bits that are sent by the transceiver on the receive path.
PHY Operating Mode 1
Configuration
Strap
MODE1
VIS
(PU)
Combined with MODE0 and MODE2, this configuration strap sets the default PHY mode.
See Note 2-3 for more information on configuration straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 30 for
additional details.
1
Receive Error
RXER
VO8
This signal is asserted to indicate that an error
was detected somewhere in the frame presently
being transferred from the transceiver.
PHY Address
0
Configuration
Strap
PHYAD0
VIS
(PD)
This configuration strap sets the transceiver’s SMI
address.
See Note 2-3 for more information on configuration straps.
Note: Refer to Section 3.7.1, "PHYAD[0]: PHY
Address Configuration," on page 26 for
additional information.
2016 Microchip Technology Inc.
DS00002165B-page 7
LAN8720A/LAN8720AI
TABLE 2-1:
RMII SIGNALS (CONTINUED)
Num Pins
Name
Symbol
Buffer
Type
1
Carrier Sense
/ Receive
Data Valid
CRS_DV
VO8
Description
This signal is asserted to indicate the receive
medium is non-idle. When a 10BASE-T packet is
received, CRS_DV is asserted, but RXD[1:0] is
held low until the SFD byte (10101011) is
received.
Note: Per the RMII standard, transmitted data is
not looped back onto the receive data
pins in 10BASE-T half-duplex mode.
PHY Operating Mode 2
Configuration
Strap
MODE2
VIS
(PU)
Combined with MODE0 and MODE1, this configuration strap sets the default PHY mode.
See Note 2-3 for more information on configuration straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 27 for
additional details.
Note 2-3
TABLE 2-2:
Configuration strap values are latched on power-on reset and system reset. Configuration straps are
identified by an underlined symbol name. Signals that function as configuration straps must be
augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration
Straps," on page 29 for additional information.
LED PINS
NUM PINS
NAME
SYMBOL
BUFFER
TYPE
LED 1
LED1
O12
DESCRIPTION
Link activity LED Indication. This pin is driven
active when a valid link is detected and blinks
when activity is detected.
Note: Refer to Section 3.8.1, "LEDs," on
page 32 for additional LED information.
Regulator Off
Configuration
Strap
1
REGOFF
IS
(PD)
This configuration strap is used to disable the
internal 1.2V regulator. When the regulator is disabled, external 1.2V must be supplied to VDDCR.
• When REGOFF is pulled high to VDD2A with
an external resistor, the internal regulator is
disabled.
• When REGOFF is floating or pulled low, the
internal regulator is enabled (default).
See Note 2-4 for more information on configuration straps.
Note: Refer to Section 3.7.4, "REGOFF:
Internal +1.2V Regulator Configuration,"
on page 32 for additional details.
DS00002165B-page 8
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 2-2:
NUM PINS
LED PINS (CONTINUED)
NAME
SYMBOL
BUFFER
TYPE
LED 2
LED2
O12
DESCRIPTION
Link Speed LED Indication. This pin is driven
active when the operating speed is 100Mbps. It is
inactive when the operating speed is 10Mbps or
during line isolation.
Note: Refer to Section 3.8.1, "LEDs," on
page 32 for additional LED information.
1
nINT/
REFCLKO
Function
Select
Configuration
Strap
nINTSEL
IS
(PU)
This configuration strap selects the mode of the
nINT/REFCLKO pin.
• When nINTSEL is floated or pulled to
VDD2A, nINT is selected for operation on the
nINT/REFCLKO pin (default).
• When nINTSEL is pulled low to VSS, REFCLKO is selected for operation on the nINT/
REFCLKO pin.
See Note 2-4 for more information on configuration straps.
Note: Refer to See Section 3.8.1.2, "nINTSEL
and LED2 Polarity Selection," on page 33
for additional information.
Note 2-4
TABLE 2-3:
Configuration strap values are latched on power-on reset and system reset. Configuration straps are
identified by an underlined symbol name. Signals that function as configuration straps must be
augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration
Straps," on page 29 for additional information.
SERIAL MANAGEMENT INTERFACE (SMI) PINS
BUFFER
TYPE
Num PINs
NAME
SYMBOL
1
SMI Data
Input/Output
MDIO
VIS/
VOD8
1
SMI Clock
MDC
VIS
TABLE 2-4:
DESCRIPTION
Serial Management Interface data input/output
Serial Management Interface clock
ETHERNET PINS
Num PINs
NAME
SYMBOL
BUFFER
TYPE
1
Ethernet TX/
RX Positive
Channel 1
TXP
AIO
Transmit/Receive Positive Channel 1
1
Ethernet TX/
RX Negative
Channel 1
TXN
AIO
Transmit/Receive Negative Channel 1
2016 Microchip Technology Inc.
DESCRIPTION
DS00002165B-page 9
LAN8720A/LAN8720AI
TABLE 2-4:
ETHERNET PINS (CONTINUED)
Num PINs
NAME
SYMBOL
BUFFER
TYPE
1
Ethernet TX/
RX Positive
Channel 2
RXP
AIO
Transmit/Receive Positive Channel 2
1
Ethernet TX/
RX Negative
Channel 2
RXN
AIO
Transmit/Receive Negative Channel 2
TABLE 2-5:
DESCRIPTION
MISCELLANEOUS PINS
Num PINs
NAME
SYMBOL
BUFFER
TYPE
1
External
Crystal
Input
XTAL1
ICLK
External crystal input
External
Clock Input
CLKIN
ICLK
Single-ended clock oscillator input.
1
External
Crystal Output
XTAL2
OCLK
1
External
Reset
nRST
VIS
(PU)
1
Interrupt Output
nINT
VOD8
(PU)
DESCRIPTION
Note: When using a single ended clock
oscillator, XTAL2 should be left
unconnected.
External crystal output
System reset. This signal is active low.
Active low interrupt output. Place an external
resistor pull-up to VDDIO.
Note: Refer to Section 3.6, "Interrupt
Management," on page 24 for additional
details on device interrupts.
Note: Refer to Section 3.8.1.2, "nINTSEL and
LED2 Polarity Selection," on page 32 for
details on how the nINTSEL configuration
strap is used to determine the function of
this pin.
Reference
Clock Output
REFCLKO
VO8
This optional 50MHz clock output is derived from
the 25MHz crystal oscillator. REFCLKO is selectable via the nINTSEL configuration strap.
Note: Refer Section 3.7.4.2, "REF_CLK Out
Mode," on page 29 for additional details.
Note: Refer to Section 3.8.1.2, "nINTSEL and
LED2 Polarity Selection," on page 32 for
details on how the nINTSEL configuration
strap is used to determine the function of
this pin.
DS00002165B-page 10
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 2-6:
ANALOG REFERENCE PINS
Num PINs
NAME
SYMBOL
BUFFER
TYPE
1
External 1%
Bias Resistor
Input
RBIAS
AI
DESCRIPTION
This pin requires connection of a 12.1k ohm (1%)
resistor to ground.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
Note: The nominal voltage is 1.2V and the
resistor will dissipate approximately 1mW
of power.
TABLE 2-7:
POWER PINS
Num PINs
NAME
SYMBOL
BUFFER
TYPE
1
+1.6V to
+3.6V Variable I/O
Power
VDDIO
P
+1.2V Digital
Core Power
Supply
VDDCR
1
DESCRIPTION
+1.6V to +3.6V variable I/O power
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
P
Supplied by the on-chip regulator unless configured for regulator off mode via the REGOFF configuration strap.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
Note: 1 uF and 470 pF decoupling capacitors in
parallel to ground should be used on this
pin.
1
1
+3.3V Channel 1 Analog
Port Power
VDD1A
+3.3V Channel 2 Analog
Port Power
VDD2A
P
+3.3V Analog Port Power to Channel 1
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
P
+3.3V Analog Port Power to Channel 2 and the
internal regulator.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
1
2.1
Ground
VSS
P
Common ground. This exposed pad must be connected to the ground plane with a via array.
Pin Assignments
2016 Microchip Technology Inc.
DS00002165B-page 11
LAN8720A/LAN8720AI
TABLE 2-8:
24-QFN PACKAGE PIN ASSIGNMENTS
Pin NUM
Pin Name
Pin NUM
Pin Name
1
VDD2A
13
MDC
2
LED2/nINTSEL
14
nINT/REFCLKO
3
LED1/REGOFF
15
nRST
4
XTAL2
16
TXEN
5
XTAL1/CLKIN
17
TXD0
6
VDDCR
18
TXD1
7
RXD1/MODE1
19
VDD1A
8
RXD0/MODE0
20
TXN
9
VDDIO
21
TXP
10
RXER/PHYAD0
22
RXN
11
CRS_DV/MODE2
23
RXP
12
MDIO
24
RBIAS
2.2
Buffer Types
TABLE 2-9:
BUFFER TYPES
BUFFER TYPE
IS
DESCRIPTION
Schmitt-triggered input
O12
Output with 12mA sink and 12mA source
VIS
Variable voltage Schmitt-triggered input
VO8
Variable voltage output with 8mA sink and 8mA source
VOD8
PU
Variable voltage open-drain output with 8mA sink
50uA (typical) internal pull-up. Unless otherwise noted in the pin description, internal pullups are always enabled.
Note: Internal pull-up resistors prevent unconnected inputs from floating. Do not rely on
internal resistors to drive signals external to the device. When connected to a load
that must be pulled high, an external resistor must be added.
PD
50uA (typical) internal pull-down. Unless otherwise noted in the pin description, internal pulldowns are always enabled.
Note: Internal pull-down resistors prevent unconnected inputs from floating. Do not rely
on internal resistors to drive signals external to the device. When connected to a
load that must be pulled low, an external resistor must be added.
AI
Analog input
AIO
Analog bi-directional
ICLK
Crystal oscillator input pin
DS00002165B-page 12
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 2-9:
BUFFER TYPES (CONTINUED)
BUFFER TYPE
OCLK
P
DESCRIPTION
Crystal oscillator output pin
Power pin
Note 2-5
The digital signals are not 5V tolerant. Refer to Section 5.1, "Absolute Maximum Ratings*," on
page 54 for additional buffer information.
Note 2-6
Sink and source capabilities are dependent on the VDDIO voltage. Refer to Section 5.1, "Absolute
Maximum Ratings*," on page 54 for additional information.
2016 Microchip Technology Inc.
DS00002165B-page 13
LAN8720A/LAN8720AI
3.0
FUNCTIONAL DESCRIPTION
This chapter provides functional descriptions of the various device features. These features have been categorized into
the following sections:
•
•
•
•
•
•
•
•
•
Transceiver
Auto-negotiation
HP Auto-MDIX Support
MAC Interface
Serial Management Interface (SMI)
Interrupt Management
Configuration Straps
Miscellaneous Functions
Application Diagrams
3.1
3.1.1
Transceiver
100BASE-TX TRANSMIT
The 100BASE-TX transmit data path is shown in Figure 3-1. Each major block is explained in the following subsections.
FIGURE 3-1:
100BASE-TX TRANSMIT DATA PATH
PLL
MAC
Ext Ref_CLK
RMII
25MHz
by 4 bits
4B/5B
Encoder
NRZI
Converter
NRZI
MLT-3
Converter
MLT-3
MLT-3
Magnetics
RMII 50Mhz by 2 bits
125 Mbps Serial
3.1.1.1
MLT-3
RJ45
25MHz by
5 bits
Scrambler
and PISO
Tx
Driver
MLT-3
CAT-5
100BASE-TX Transmit Data Across the RMII Interface
The MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate valid data. The data is
latched by the transceiver’s RMII block on the rising edge of REF_CLK. The data is in the form of 2-bit wide 50MHz data.
3.1.1.2
4B/5B Encoding
The transmit data passes from the RMII block to the 4B/5B encoder. This block encodes the data from 4-bit nibbles to
5-bit symbols (known as “code-groups”) according to Table 3-1. Each 4-bit data-nibble is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used for control information or are not valid.
The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles, 0 through F. The
remaining code-groups are given letter designations with slashes on either side. For example, an IDLE code-group is /
I/, a transmit error code-group is /H/, etc.
DS00002165B-page 14
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 3-1:
4B/5B CODE TABLE
CODE
GROUP
SYM
11110
0
0
0000
DATA
0
0000
DATA
01001
1
1
0001
—
1
0001
—
10100
2
2
0010
—
2
0010
—
10101
3
3
0011
—
3
0011
—
01010
4
4
0100
—
4
0100
—
01011
5
5
0101
—
5
0101
—
01110
6
6
0110
—
6
0110
—
01111
7
7
0111
—
7
0111
—
10010
8
8
1000
—
8
1000
—
10011
9
9
1001
—
9
1001
—
10110
A
A
1010
—
A
1010
—
10111
B
B
1011
—
B
1011
—
11010
C
C
1100
—
C
1100
—
11011
D
D
1101
—
D
1101
—
11100
E
E
1110
—
E
1110
—
11101
F
F
1111
—
F
1111
—
11111
I
IDLE
Sent after /T/R until TXEN
11000
J
First nibble of SSD, translated to “0101”
following IDLE, else RXER
Sent for rising TXEN
10001
K
Second nibble of SSD, translated to
“0101” following J, else RXER
Sent for rising TXEN
01101
T
First nibble of ESD, causes de-assertion
of CRS if followed by /R/, else assertion
of RXER
Sent for falling TXEN
00111
R
Second nibble of ESD, causes deassertion of CRS if following /T/, else assertion
of RXER
Sent for falling TXEN
00100
H
Transmit Error Symbol
Sent for rising TXER
00110
V
INVALID, RXER if during RXDV
INVALID
11001
V
INVALID, RXER if during RXDV
INVALID
00000
V
INVALID, RXER if during RXDV
INVALID
00001
V
INVALID, RXER if during RXDV
INVALID
00010
V
INVALID, RXER if during RXDV
INVALID
00011
V
INVALID, RXER if during RXDV
INVALID
2016 Microchip Technology Inc.
RECEIVER
INTERPRETATION
TRANSMITTER
INTERPRETATION
DS00002165B-page 15
LAN8720A/LAN8720AI
TABLE 3-1:
4B/5B CODE TABLE (CONTINUED)
CODE
GROUP
SYM
00101
V
INVALID, RXER if during RXDV
INVALID
01000
V
INVALID, RXER if during RXDV
INVALID
01100
V
INVALID, RXER if during RXDV
INVALID
10000
V
INVALID, RXER if during RXDV
INVALID
3.1.1.3
RECEIVER
INTERPRETATION
TRANSMITTER
INTERPRETATION
Scrambling
Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large narrow-band
peaks. Scrambling the data helps eliminate these peaks and spread the signal power more uniformly over the entire
channel bandwidth. This uniform spectral density is required by FCC regulations to prevent excessive EMI from being
radiated by the physical wiring.
The seed for the scrambler is generated from the transceiver address, PHYAD, ensuring that in multiple-transceiver
applications, such as repeaters or switches, each transceiver will have its own scrambler sequence.
The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data.
3.1.1.4
NRZI and MLT-3 Encoding
The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a serial 125MHz NRZI
data stream. The NRZI is encoded to MLT-3. MLT-3 is a tri-level code where a change in the logic level represents a
code bit “1” and the logic output remaining at the same level represents a code bit “0”.
3.1.1.5
100M Transmit Driver
The MLT3 data is then passed to the analog transmitter, which drives the differential MLT-3 signal, on outputs TXP and
TXN, to the twisted pair media across a 1:1 ratio isolation transformer. The 10BASE-T and 100BASE-TX signals pass
through the same transformer so that common “magnetics” can be used for both. The transmitter drives into the 100
impedance of the CAT-5 cable. Cable termination and impedance matching require external components.
3.1.1.6
100M Phase Lock Loop (PLL)
The 100M PLL locks onto reference clock and generates the 125MHz clock used to drive the 125 MHz logic and the
100BASE-TX transmitter.
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LAN8720A/LAN8720AI
3.1.2
100BASE-TX RECEIVE
The 100BASE-TX receive data path is shown in Figure 3-2. Each major block is explained in the following subsections.
FIGURE 3-2:
100BASE-TX RECEIVE DATA PATH
PLL
MAC
Ext Ref_CLK
RMII 50Mhz by 2 bits
25MHz
by 4 bits
RMII
4B/5B
Decoder
25MHz by
5 bits
Descrambler
and SIPO
125 Mbps Serial
NRZI
Converter
A/D
Converter
NRZI
MLT-3
MLT-3
Converter
Magnetics
MLT-3
MLT-3
RJ45
DSP: Timing
recovery, Equalizer
and BLW Correction
MLT-3
CAT-5
6 bit Data
3.1.2.1
100M Receive Input
The MLT-3 from the cable is fed into the transceiver (on inputs RXP and RXN) via a 1:1 ratio transformer. The ADC
samples the incoming differential signal at a rate of 125M samples per second. Using a 64-level quanitizer, it generates
6 digital bits to represent each sample. The DSP adjusts the gain of the ADC according to the observed signal levels
such that the full dynamic range of the ADC can be used.
3.1.2.2
Equalizer, Baseline Wander Correction and Clock and Data Recovery
The 6 bits from the ADC are fed into the DSP block. The equalizer in the DSP section compensates for phase and amplitude distortion caused by the physical channel consisting of magnetics, connectors, and CAT- 5 cable. The equalizer
can restore the signal for any good-quality CAT-5 cable between 1m and 150m.
If the DC content of the signal is such that the low-frequency components fall below the low frequency pole of the isolation transformer, then the droop characteristics of the transformer will become significant and Baseline Wander (BLW)
on the received signal will result. To prevent corruption of the received data, the transceiver corrects for BLW and can
receive the ANSI X3.263-1995 FDDI TP-PMD defined “killer packet” with no bit errors.
The 100M PLL generates multiple phases of the 125MHz clock. A multiplexer, controlled by the timing unit of the DSP,
selects the optimum phase for sampling the data. This is used as the received recovered clock. This clock is used to
extract the serial data from the received signal.
3.1.2.3
NRZI and MLT-3 Decoding
The DSP generates the MLT-3 recovered levels that are fed to the MLT-3 converter. The MLT-3 is then converted to an
NRZI data stream.
3.1.2.4
Descrambling
The descrambler performs an inverse function to the scrambler in the transmitter and also performs the Serial In Parallel
Out (SIPO) conversion of the data.
During reception of IDLE (/I/) symbols. the descrambler synchronizes its descrambler key to the incoming stream. Once
synchronization is achieved, the descrambler locks on this key and is able to descramble incoming data.
2016 Microchip Technology Inc.
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Special logic in the descrambler ensures synchronization with the remote transceiver by searching for IDLE symbols
within a window of 4000 bytes (40us). This window ensures that a maximum packet size of 1514 bytes, allowed by the
IEEE 802.3 standard, can be received with no interference. If no IDLE-symbols are detected within this time-period,
receive operation is aborted and the descrambler re-starts the synchronization process.
3.1.2.5
Alignment
The de-scrambled signal is then aligned into 5-bit code-groups by recognizing the /J/K/ Start-of-Stream Delimiter (SSD)
pair at the start of a packet. Once the code-word alignment is determined, it is stored and utilized until the next start of
frame.
3.1.2.6
5B/4B Decoding
The 5-bit code-groups are translated into 4-bit data nibbles according to the 4B/5B table. The translated data is presented on the RXD[1:0] signal lines. The SSD, /J/K/, is translated to “0101 0101” as the first 2 nibbles of the MAC preamble. Reception of the SSD causes the transceiver to assert the receive data valid signal, indicating that valid data is
available on the RXD bus. Successive valid code-groups are translated to data nibbles. Reception of either the End of
Stream Delimiter (ESD) consisting of the /T/R/ symbols, or at least two /I/ symbols causes the transceiver to de-assert
the carrier sense and receive data valid signals.
Note:
3.1.2.7
These symbols are not translated into data.
Receive Data Valid Signal
The Receive Data Valid signal (RXDV) indicates that recovered and decoded nibbles are being presented on the
RXD[1:0] outputs synchronous to RXCLK. RXDV becomes active after the /J/K/ delimiter has been recognized and RXD
is aligned to nibble boundaries. It remains active until either the /T/R/ delimiter is recognized or link test indicates failure
or SIGDET becomes false.
RXDV is asserted when the first nibble of translated /J/K/ is ready for transfer over the Media Independent Interface (MII
mode).
FIGURE 3-3:
RELATIONSHIP BETWEEN RECEIVED DATA AND SPECIFIC MII SIGNALS
CLEAR-TEXT
J
K
5
5
5
D
data
data
data
data
T
R
5
5
5
5
5
D
data
data
data
data
Idle
RX_CLK
RX_DV
RXD
3.1.2.8
Receiver Errors
During a frame, unexpected code-groups are considered receive errors. Expected code groups are the DATA set (0
through F), and the /T/R/ (ESD) symbol pair. When a receive error occurs, the RXER signal is asserted and arbitrary
data is driven onto the RXD[1:0] lines. Should an error be detected during the time that the /J/K/ delimiter is being
decoded (bad SSD error), RXER is asserted true and the value ‘1110’ is driven onto the RXD[1:0] lines. Note that the
Valid Data signal is not yet asserted when the bad SSD error occurs.
3.1.2.9
100M Receive Data Across the RMII Interface
The 2-bit data nibbles are sent to the RMII block. These data nibbles are clocked to the controller at a rate of 50MHz.
The controller samples the data on the rising edge of XTAL1/CLKIN (REF_CLK). To ensure that the setup and hold
requirements are met, the nibbles are clocked out of the transceiver on the falling edge of XTAL1/CLKIN (REF_CLK).
3.1.3
10BASE-T TRANSMIT
Data to be transmitted comes from the MAC layer controller. The 10BASE-T transmitter receives 4-bit nibbles from the
MII at a rate of 2.5MHz and converts them to a 10Mbps serial data stream. The data stream is then Manchester-encoded
and sent to the analog transmitter, which drives a signal onto the twisted pair via the external magnetics.
The 10M transmitter uses the following blocks:
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2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
•
•
•
•
MII (digital)
TX 10M (digital)
10M Transmitter (analog)
10M PLL (analog)
3.1.3.1
10M Transmit Data Across the RMII Interface
The MAC controller drives the transmit data onto the TXD bus. TXD[1:0] shall transition synchronously with respect to
REF_CLK. When TXEN is asserted, TXD[1:0] are accepted for transmission by the device. TXD[1:0] shall be “00” to
indicate idle when TXEN is deasserted. Values of TXD[1:0] other than “00” when TXEN is deasserted are reserved for
out-of-band signaling (to be defined). Values other than “00” on TXD[1:0] while TXEN is deasserted shall be ignored by
the device.TXD[1:0] shall provide valid data for each REF_CLK period while TXEN is asserted.
In order to comply with legacy 10BASE-T MAC/Controllers, in half-duplex mode the transceiver loops back the transmitted data, on the receive path. This does not confuse the MAC/Controller since the COL signal is not asserted during
this time. The transceiver also supports the SQE (Heartbeat) signal.
3.1.3.2
Manchester Encoding
The 4-bit wide data is sent to the 10M TX block. The nibbles are converted to a 10Mbps serial NRZI data stream. The
10M PLL locks onto the external clock or internal oscillator and produces a 20MHz clock. This is used to Manchester
encode the NRZ data stream. When no data is being transmitted (TXEN is low), the 10M TX block outputs Normal Link
Pulses (NLPs) to maintain communications with the remote link partner.
3.1.3.3
10M Transmit Drivers
The Manchester encoded data is sent to the analog transmitter where it is shaped and filtered before being driven out
as a differential signal across the TXP and TXN outputs.
3.1.4
10BASE-T RECEIVE
The 10BASE-T receiver gets the Manchester- encoded analog signal from the cable via the magnetics. It recovers the
receive clock from the signal and uses this clock to recover the NRZI data stream. This 10M serial data is converted to
4-bit data nibbles which are passed to the controller via MII at a rate of 2.5MHz.
This 10M receiver uses the following blocks:
•
•
•
•
Filter and SQUELCH (analog)
10M PLL (analog)
RX 10M (digital)
MII (digital)
3.1.4.1
10M Receive Input and Squelch
The Manchester signal from the cable is fed into the transceiver (on inputs RXP and RXN) via 1:1 ratio magnetics. It is
first filtered to reduce any out-of-band noise. It then passes through a SQUELCH circuit. The SQUELCH is a set of
amplitude and timing comparators that normally reject differential voltage levels below 300mV and detect and recognize
differential voltages above 585mV.
3.1.4.2
Manchester Decoding
The output of the SQUELCH goes to the 10M RX block where it is validated as Manchester encoded data. The polarity
of the signal is also checked. If the polarity is reversed (local RXP is connected to RXN of the remote partner and vice
versa), the condition is identified and corrected. The reversed condition is indicated by the XPOL bit of the Special Control/Status Indications Register. The 10M PLL is locked onto the received Manchester signal, from which the 20MHz
cock is generated. Using this clock, the Manchester encoded data is extracted and converted to a 10MHz NRZI data
stream. It is then converted from serial to 4-bit wide parallel data.
The 10M RX block also detects valid 10Base-T IDLE signals - Normal Link Pulses (NLPs) - to maintain the link.
3.1.4.3
10M Receive Data Across the RMII Interface
The 2-bit data nibbles are sent to the RMII block. These data nibbles are valid on the rising edge of the RMII REF_CLK.
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LAN8720A/LAN8720AI
3.1.4.4
Jabber Detection
Jabber is a condition in which a station transmits for a period of time longer than the maximum permissible packet length,
usually due to a fault condition, which results in holding the TXEN input for a long period. Special logic is used to detect
the jabber state and abort the transmission to the line within 45ms. Once TXEN is deasserted, the logic resets the jabber
condition.
As shown in Section 4.2.2, "Basic Status Register," on page 45, the Jabber Detect bit indicates that a jabber condition
was detected.
3.2
Auto-negotiation
The purpose of the auto-negotiation function is to automatically configure the transceiver to the optimum link parameters
based on the capabilities of its link partner. Auto-negotiation is a mechanism for exchanging configuration information
between two link-partners and automatically selecting the highest performance mode of operation supported by both
sides. Auto-negotiation is fully defined in clause 28 of the IEEE 802.3 specification.
Once auto-negotiation has completed, information about the resolved link can be passed back to the controller via the
Serial Management Interface (SMI). The results of the negotiation process are reflected in the Speed Indication bits of
the PHY Special Control/Status Register, as well as in the Auto Negotiation Link Partner Ability Register. The auto-negotiation protocol is a purely physical layer activity and proceeds independently of the MAC controller.
The advertised capabilities of the transceiver are stored in the Auto Negotiation Advertisement Register. The default
advertised by the transceiver is determined by user-defined on-chip signal options.
The following blocks are activated during an Auto-negotiation session:
•
•
•
•
•
•
•
Auto-negotiation (digital)
100M ADC (analog)
100M PLL (analog)
100M equalizer/BLW/clock recovery (DSP)
10M SQUELCH (analog)
10M PLL (analog)
10M Transmitter (analog)
When enabled, auto-negotiation is started by the occurrence of one of the following events:
•
•
•
•
•
Hardware reset
Software reset
Power-down reset
Link status down
Setting the Restart Auto-Negotiate bit of the Basic Control Register
On detection of one of these events, the transceiver begins auto-negotiation by transmitting bursts of Fast Link Pulses
(FLP), which are bursts of link pulses from the 10M transmitter. They are shaped as Normal Link Pulses and can pass
uncorrupted down CAT-3 or CAT-5 cable. A Fast Link Pulse Burst consists of up to 33 pulses. The 17 odd-numbered
pulses, which are always present, frame the FLP burst. The 16 even-numbered pulses, which may be present or absent,
contain the data word being transmitted. Presence of a data pulse represents a “1”, while absence represents a “0”.
The data transmitted by an FLP burst is known as a “Link Code Word.” These are defined fully in IEEE 802.3 clause 28.
In summary, the transceiver advertises 802.3 compliance in its selector field (the first 5 bits of the Link Code Word). It
advertises its technology ability according to the bits set in the Auto Negotiation Advertisement Register.
There are 4 possible matches of the technology abilities. In the order of priority these are:
•
•
•
•
100M Full Duplex (Highest Priority)
100M Half Duplex
10M Full Duplex
10M Half Duplex (Lowest Priority)
If the full capabilities of the transceiver are advertised (100M, Full Duplex), and if the link partner is capable of 10M and
100M, then auto-negotiation selects 100M as the highest performance mode. If the link partner is capable of half and
full duplex modes, then auto-negotiation selects full duplex as the highest performance operation.
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LAN8720A/LAN8720AI
Once a capability match has been determined, the link code words are repeated with the acknowledge bit set. Any difference in the main content of the link code words at this time will cause auto-negotiation to re-start. Auto-negotiation
will also re-start if not all of the required FLP bursts are received.
The capabilities advertised during auto-negotiation by the transceiver are initially determined by the logic levels latched
on the MODE[2:0] configuration straps after reset completes. These configuration straps can also be used to disable
auto-negotiation on power-up. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page 30 for additional information.
Writing the bits 8 through 5 of the Auto Negotiation Advertisement Register allows software control of the capabilities
advertised by the transceiver. Writing the Auto Negotiation Advertisement Register does not automatically re-start autonegotiation. The Restart Auto-Negotiate bit of the Basic Control Register must be set before the new abilities will be
advertised. Auto-negotiation can also be disabled via software by clearing the Auto-Negotiation Enable bit of the Basic
Control Register.
Note:
3.2.1
The device does not support “Next Page” capability.
PARALLEL DETECTION
If the LAN8720A/LAN8720Ai is connected to a device lacking the ability to auto-negotiate (for example, no FLPs are
detected), it is able to determine the speed of the link based on either 100M MLT-3 symbols or 10M Normal Link Pulses.
In this case the link is presumed to be half duplex per the IEEE standard. This ability is known as “Parallel Detection.”
This feature ensures interoperability with legacy link partners. If a link is formed via parallel detection, then the Link Partner Auto-Negotiation Able bit of the Auto Negotiation Expansion Register is cleared to indicate that the Link Partner is
not capable of auto-negotiation. The controller has access to this information via the management interface. If a fault
occurs during parallel detection, the Parallel Detection Fault bit of Link Partner Auto-Negotiation Able is set.
Auto Negotiation Link Partner Ability Register is used to store the link partner ability information, which is coded in the
received FLPs. If the link partner is not auto-negotiation capable, then the Auto Negotiation Link Partner Ability Register
is updated after completion of parallel detection to reflect the speed capability of the link partner.
3.2.2
RESTARTING AUTO-NEGOTIATION
Auto-negotiation can be restarted at any time by setting the Restart Auto-Negotiate bit of the Basic Control Register.
Auto-negotiation will also restart if the link is broken at any time. A broken link is caused by signal loss. This may occur
because of a cable break, or because of an interruption in the signal transmitted by the link partner. Auto-negotiation
resumes in an attempt to determine the new link configuration.
If the management entity re-starts auto-negotiation by setting the Restart Auto-Negotiate bit of the Basic Control Register, the LAN8720A/LAN8720Ai will respond by stopping all transmission/receiving operations. Once the break_link_timer is completed in the Auto-negotiation state-machine (approximately 1200ms), auto-negotiation will re-start. In this
case, the link partner will have also dropped the link due to lack of a received signal, so it too will resume auto-negotiation.
3.2.3
DISABLING AUTO-NEGOTIATION
Auto-negotiation can be disabled by setting the Auto-Negotiation Enable bit of the Basic Control Register to zero. The
device will then force its speed of operation to reflect the information in the Basic Control Register (Speed Select bit and
Duplex Mode bit). These bits should be ignored when auto-negotiation is enabled.
3.2.4
HALF VS. FULL DUPLEX
Half duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle network traffic and collisions. In this mode, the carrier sense signal, CRS, responds to both transmit and receive activity. If
data is received while the transceiver is transmitting, a collision results.
In full duplex mode, the transceiver is able to transmit and receive data simultaneously. In this mode, CRS responds
only to receive activity. The CSMA/CD protocol does not apply and collision detection is disabled.
3.3
HP Auto-MDIX Support
HP Auto-MDIX facilitates the use of CAT-3 (10BASE-T) or CAT-5 (100BASE-T) media UTP interconnect cable without
consideration of interface wiring scheme. If a user plugs in either a direct connect LAN cable, or a cross-over patch
cable, as shown in Figure 3-4, the device’s Auto-MDIX transceiver is capable of configuring the TXP/TXN and RXP/RXN
pins for correct transceiver operation.
2016 Microchip Technology Inc.
DS00002165B-page 21
LAN8720A/LAN8720AI
The internal logic of the device detects the TX and RX pins of the connecting device. Since the RX and TX line pairs
are interchangeable, special PCB design considerations are needed to accommodate the symmetrical magnetics and
termination of an Auto-MDIX design.
The Auto-MDIX function can be disabled via the AMDIXCTRL bit in the Special Control/Status Indications Register.
FIGURE 3-4:
DIRECT CABLE CONNECTION VS. CROSS-OVER CABLE CONNECTION
RJ-45 8-pin straight-through
for 10BASE-T/100BASE-TX
signaling
RJ-45 8-pin cross-over for
10BASE-T/100BASE-TX
signaling
TXP
1
1
TXP
TXP
1
1
TXP
TXN
2
2
TXN
TXN
2
2
TXN
RXP
3
3
RXP
RXP
3
3
RXP
Not Used
4
4
Not Used
Not Used
4
4
Not Used
Not Used
5
5
Not Used
Not Used
5
5
Not Used
RXN
6
6
RXN
RXN
6
6
RXN
Not Used
7
7
Not Used
Not Used
7
7
Not Used
Not Used
8
8
Not Used
Not Used
8
8
Not Used
Direct Connect Cable
3.4
3.4.1
Cross-Over Cable
MAC Interface
RMII
The device supports the low pin count Reduced Media Independent Interface (RMII) intended for use between Ethernet
transceivers and switch ASICs. Under IEEE 802.3, an MII comprised of 16 pins for data and control is defined. In devices
incorporating many MACs or transceiver interfaces such as switches, the number of pins can add significant cost as the
port counts increase. RMII reduces this pin count while retaining a management interface (MDIO/MDC) that is identical
to MII.
The RMII interface has the following characteristics:
•
•
•
•
It is capable of supporting 10Mbps and 100Mbps data rates
A single clock reference is used for both transmit and receive
It provides independent 2-bit (di-bit) wide transmit and receive data paths
It uses LVCMOS signal levels, compatible with common digital CMOS ASIC processes
The RMII includes the following interface signals (1 optional):
•
•
•
•
•
•
transmit data - TXD[1:0]
transmit strobe - TXEN
receive data - RXD[1:0]
receive error - RXER (Optional)
carrier sense - CRS_DV
Reference Clock - (RMII references usually define this signal as REF_CLK)
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LAN8720A/LAN8720AI
3.4.1.1
CRS_DV - Carrier Sense/Receive Data Valid
The CRS_DV is asserted by the device when the receive medium is non-idle. CRS_DV is asserted asynchronously on
detection of carrier due to the criteria relevant to the operating mode. In 10BASE-T mode when squelch is passed, or
in 100BASE-X mode when 2 non-contiguous zeros in 10 bits are detected, the carrier is said to be detected.
Loss of carrier shall result in the deassertion of CRS_DV synchronous to the cycle of REF_CLK which presents the first
di-bit of a nibble onto RXD[1:0] (for example, CRS_DV is deasserted only on nibble boundaries). If the device has additional bits to be presented on RXD[1:0] following the initial deassertion of CRS_DV, then the device shall assert
CRS_DV on cycles of REF_CLK which present the second di-bit of each nibble and de-assert CRS_DV on cycles of
REF_CLK which present the first di-bit of a nibble. The result is, starting on nibble boundaries, CRS_DV toggles at 25
MHz in 100Mbps mode and 2.5 MHz in 10Mbps mode when CRS ends before RXDV (for example, the FIFO still has
bits to transfer when the carrier event ends). Therefore, the MAC can accurately recover RXDV and CRS.
During a false carrier event, CRS_DV shall remain asserted for the duration of carrier activity. The data on RXD[1:0] is
considered valid once CRS_DV is asserted. However, since the assertion of CRS_DV is asynchronous relative to
REF_CLK, the data on RXD[1:0] shall be “00” until proper receive signal decoding takes place.
3.4.1.2
Reference Clock (REF_CLK)
The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_DV, RXD[1:0], TXEN, TXD[1:0]
and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path.
However, on the receive data path, the receiver recovers the clock from the incoming data stream, and the device uses
elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK.
3.5
Serial Management Interface (SMI)
The Serial Management Interface is used to control the device and obtain its status. This interface supports registers 0
through 6 as required by Clause 22 of the 802.3 standard, as well as “vendor-specific” registers 16 to 31 allowed by the
specification. Non-supported registers (such as 7 to 15) will be read as hexadecimal “FFFF”. Device registers are
detailed in Section 4.0, "Register Descriptions," on page 43.
At the system level, SMI provides 2 signals: MDIO and MDC. The MDC signal is an aperiodic clock provided by the
station management controller (SMC). MDIO is a bi-directional data SMI input/output signal that receives serial data
(commands) from the controller SMC and sends serial data (status) to the SMC. The minimum time between edges of
the MDC is 160 ns. There is no maximum time between edges. The minimum cycle time (time between two consecutive
rising or two consecutive falling edges) is 400 ns. These modest timing requirements allow this interface to be easily
driven by the I/O port of a microcontroller.
The data on the MDIO line is latched on the rising edge of the MDC. The frame structure and timing of the data is shown
in Figure 3-5 and Figure 3-6. The timing relationships of the MDIO signals are further described in Section 5.5.6, "SMI
Timing," on page 64.
FIGURE 3-5:
MDIO TIMING AND FRAME STRUCTURE - READ CYCLE
Read Cycle
MDC
MDIO
32 1's
Preamble
0
1
Start of
Frame
1
0
OP
Code
A4
A3
A2
A1
PHY Address
Data To Phy
2016 Microchip Technology Inc.
A0 R4 R3 R2 R1 R0
Register Address
D15
Turn
Around
D14
...
...
D1
D0
Data
Data From Phy
DS00002165B-page 23
LAN8720A/LAN8720AI
FIGURE 3-6:
MDIO TIMING AND FRAME STRUCTURE - WRITE CYCLE
Write Cycle
MDC
MDIO
32 1's
Preamble
0
1
Start of
Frame
0
1
A4
OP
Code
A3
A2
A1
PHY Address
A0 R4 R3 R2 R1 R0
Register Address
D15
Turn
Around
D14
...
...
D1
D0
Data
Data To Phy
3.6
Interrupt Management
The device management interface supports an interrupt capability that is not a part of the IEEE 802.3 specification. This
interrupt capability generates an active low asynchronous interrupt signal on the nINT output whenever certain events
are detected as setup by the Interrupt Mask Register.
The device’s interrupt system provides two modes, a Primary Interrupt mode and an Alternative interrupt mode. Both
systems will assert the nINT pin low when the corresponding mask bit is set. These modes differ only in how they deassert the nINT interrupt output. These modes are detailed in the following subsections.
Note:
3.6.1
The Primary interrupt mode is the default interrupt mode after a power-up or hard reset. The Alternative
interrupt mode requires setup after a power-up or hard reset.
PRIMARY INTERRUPT SYSTEM
The Primary interrupt system is the default interrupt mode (ALTINT bit of the Mode Control/Status Register is “0”). The
Primary interrupt system is always selected after power-up or hard reset. In this mode, to set an interrupt, set the corresponding mask bit in the Interrupt Mask Register (see Table 3-3). Then when the event to assert nINT is true, the nINT
output will be asserted. When the corresponding event to deassert nINT is true, then the nINT will be de-asserted.
TABLE 3-2:
Mask
INTERRUPT MANAGEMENT TABLE
Interrupt Source Flag
Interrupt Source
Event to Assert
nINT
Event to
De-Assert nINT
30.7
29.7
ENERGYON
17.1
ENERGYON
Rising 17.1
(Note 3-3)
Falling 17.1 or
Reading register 29
30.6
29.6
Auto-Negotiation
complete
1.5
Auto-Negotiate
Complete
Rising 1.5
Falling 1.5 or
Reading register 29
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2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 3-2:
INTERRUPT MANAGEMENT TABLE
30.5
29.5
Remote Fault
Detected
1.4
Remote Fault
Rising 1.4
Falling 1.4, or
Reading register 1 or
Reading register 29
30.4
29.4
Link Down
1.2
Link Status
Falling 1.2
Reading register 1 or
Reading register 29
30.3
29.3
Auto-Negotiation
LP Acknowledge
5.14
Acknowledge
Rising 5.14
Falling 5.14 or
Read register 29
30.2
29.2
Parallel Detection
Fault
6.4
Parallel Detection Fault
Rising 6.4
Falling 6.4 or
Reading register 6, or
Reading register 29
or
Re-Auto Negotiate or
Link down
30.1
29.1
Auto-Negotiation
Page Received
6.1
Page Received
Rising 6.1
Falling of 6.1 or
Reading register 6, or
Reading register 29
Re-Auto Negotiate, or
Link Down.
Note 3-1
Note:
3.6.2
If the mask bit is enabled and nINT has been de-asserted while ENERGYON is still high, nINT will
assert for 256 ms, approximately one second after ENERGYON goes low when the Cable is
unplugged. To prevent an unexpected assertion of nINT, the ENERGYON interrupt mask should
always be cleared as part of the ENERGYON interrupt service routine.
The ENERGYON bit in the Mode Control/Status Register is defaulted to a ‘1’ at the start of the signal acquisition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no
signal is present, then both ENERGYON and INT7 will clear within a few milliseconds.
ALTERNATE INTERRUPT SYSTEM
The Alternate interrupt system is enabled by setting the ALTINT bit of the Mode Control/Status Register to “1”. In this
mode, to set an interrupt, set the corresponding bit of the in the Mask Register 30, (see Table 3-4). To Clear an interrupt,
either clear the corresponding bit in the Interrupt Mask Register to deassert the nINT output, or clear the interrupt
source, and write a ‘1’ to the corresponding Interrupt Source Flag. Writing a ‘1’ to the Interrupt Source Flag will cause
the state machine to check the Interrupt Source to determine if the Interrupt Source Flag should clear or stay as a ‘1’. If
the Condition to deassert is true, then the Interrupt Source Flag is cleared and nINT is also deasserted. If the Condition
to deassert is false, then the Interrupt Source Flag remains set, and the nINT remains asserted.
2016 Microchip Technology Inc.
DS00002165B-page 25
LAN8720A/LAN8720AI
For example, setting the INT7 bit in the Interrupt Mask Register will enable the ENERGYON interrupt. After a cable is
plugged in, the ENERGYON bit in the Mode Control/Status Register goes active and nINT will be asserted low. To deassert the nINT interrupt output, either clear the ENERGYON bit in the Mode Control/Status Register by removing the
cable and then writing a ‘1’ to the INT7 bit in the Interrupt Mask Register, OR clear the INT7 mask (bit 7 of the Interrupt
Mask Register).
TABLE 3-3:
Mask
ALTERNATIVE INTERRUPT SYSTEM MANAGEMENT TABLE
Interrupt Source Flag
Interrupt Source
Event to
Assert nINT
Condition to
De-Assert
Bit to
Clear
nINT
30.7
29.7
ENERGYON
17.1
ENERGYON
Rising 17.1
17.1 low
29.7
30.6
29.6
Auto-Negotiation
complete
1.5
Auto-Negotiate
Complete
Rising 1.5
1.5 low
29.6
30.5
29.5
Remote Fault
Detected
1.4
Remote Fault
Rising 1.4
1.4 low
29.5
30.4
29.4
Link Down
1.2
Link Status
Falling 1.2
1.2 high
29.4
30.3
29.3
Auto-Negotiation
LP Acknowledge
5.14
Acknowledge
Rising 5.14
5.14 low
29.3
30.2
29.2
Parallel Detection Fault
6.4
Parallel Detection Fault
Rising 6.4
6.4 low
29.2
30.1
29.1
Auto-Negotiation
Page Received
6.1
Page Received
Rising 6.1
6.1 low
29.1
The ENERGYON bit in the Mode Control/Status Register is defaulted to a ‘1’ at the start of the signal acquisition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no
signal is present, then both ENERGYON and INT7 will clear within a few milliseconds.
Note:
3.7
Configuration Straps
Configuration straps allow various features of the device to be automatically configured to user defined values. Configuration straps are latched upon Power-On Reset (POR) and pin reset (nRST). Configuration straps include internal
resistors in order to prevent the signal from floating when unconnected. If a particular configuration strap is connected
to a load, an external pull-up or pull-down resistor should be used to augment the internal resistor to ensure that it
reaches the required voltage level prior to latching. The internal resistor can also be overridden by the addition of an
external resistor.
Note 3-2
The system designer must guarantee that configuration strap pins meet the timing requirements
specified in Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page 59. If
configuration strap pins are not at the correct voltage level prior to being latched, the device may
capture incorrect strap values.
Note 3-3
When externally pulling configuration straps high, the strap should be tied to VDDIO, except for
REGOFF and nINTSEL which should be tied to VDD2A.
3.7.1
PHYAD[0]: PHY ADDRESS CONFIGURATION
The PHYAD0 bit is driven high or low to give each PHY a unique address. This address is latched into an internal register
at the end of a hardware reset (default = 0b). In a multi-PHY application (such as a repeater), the controller is able to
manage each PHY via the unique address. Each PHY checks each management data frame for a matching address in
the relevant bits. When a match is recognized, the PHY responds to that particular frame. The PHY address is also used
to seed the scrambler. In a multi-PHY application, this ensures that the scramblers are out of synchronization and disperses the electromagnetic radiation across the frequency spectrum.
DS00002165B-page 26
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
The device’s SMI address may be configured using hardware configuration to either the value 0 or 1. The user can configure the PHY address using Software Configuration if an address greater than 1 is required. The PHY address can be
written (after SMI communication at some address is established) using the PHYAD bits of the Special Modes Register.
The PHYAD0 hardware configuration strap is multiplexed with the RXER pin.
3.7.2
MODE[2:0]: MODE CONFIGURATION
The MODE[2:0] configuration straps control the configuration of the 10/100 digital block. When the nRST pin is deasserted, the register bit values are loaded according to the MODE[2:0] configuration straps. The 10/100 digital block is
then configured by the register bit values. When a soft reset occurs via the Soft Reset bit of the Basic Control Register,
the configuration of the 10/100 digital block is controlled by the register bit values and the MODE[2:0] configuration
straps have no affect.
The device’s mode may be configured using the hardware configuration straps as summarized in Table 3-6. The user
may configure the transceiver mode by writing the SMI registers.
TABLE 3-4:
MODE[2:0] BUS
Default Register Bit Values
MODE[2:0]
Mode Definitions
Register 0
Register 4
[13,12,10,8]
[8,7,6,5]
000
10Base-T Half Duplex. Auto-negotiation disabled.
0000
N/A
001
10Base-T Full Duplex. Auto-negotiation disabled.
0001
N/A
010
100Base-TX Half Duplex. Auto-negotiation disabled.
CRS is active during Transmit & Receive.
1000
N/A
011
100Base-TX Full Duplex. Auto-negotiation disabled.
CRS is active during Receive.
1001
N/A
100
100Base-TX Half Duplex is advertised. Auto-negotiation enabled.
CRS is active during Transmit & Receive.
1100
0100
101
Repeater mode. Auto-negotiation enabled.
100Base-TX Half Duplex is advertised.
CRS is active during Receive.
1100
0100
110
Power Down mode. In this mode the transceiver will
wake-up in Power-Down mode. The transceiver
cannot be used when the MODE[2:0] bits are set to
this mode. To exit this mode, the MODE bits in Register 18.7:5(see Section 4.2.9, "Special Modes Register," on page 50) must be configured to some
other value and a soft reset must be issued.
N/A
N/A
111
All capable. Auto-negotiation enabled.
X10X
1111
The MODE[2:0] hardware configuration pins are multiplexed with other signals as shown in Table 3-5.
TABLE 3-5:
2016 Microchip Technology Inc.
PIN NAMES FOR MODE BITS
MODE Bit
Pin Name
MODE[0]
RXD0/MODE0
MODE[1]
RXD1/MODE1
DS00002165B-page 27
LAN8720A/LAN8720AI
TABLE 3-5:
3.7.3
PIN NAMES FOR MODE BITS
MODE Bit
Pin Name
MODE[2]
CRS_DV/MODE2
REGOFF: INTERNAL +1.2V REGULATOR CONFIGURATION
The incorporation of flexPWR technology provides the ability to disable the internal +1.2V regulator. When the regulator
is disabled, an external +1.2V must be supplied to the VDDCR pin. Disabling the internal +1.2V regulator makes it possible to reduce total system power, since an external switching regulator with greater efficiency (versus the internal linear
regulator) can be used to provide +1.2V to the transceiver circuitry.
Note:
3.7.3.1
Because the REGOFF configuration strap shares functionality with the LED1 pin, proper consideration must
also be given to the LED polarity. Refer to Section 3.8.1.1, "REGOFF and LED1 Polarity Selection," on
page 33 for additional information on the relation between REGOFF and the LED1 polarity.
Disabling the Internal +1.2V Regulator
To disable the +1.2V internal regulator, a pull-up strapping resistor should be connected from the REGOFF configuration
strap to VDD2A. At power-on, after both VDDIO and VDD2A are within specification, the transceiver will sample
REGOFF to determine whether the internal regulator should turn on. If the pin is sampled at a voltage greater than VIH,
then the internal regulator is disabled and the system must supply +1.2V to the VDDCR pin. The VDDIO voltage must
be at least 80% of the operating voltage level (1.44V when operating at 1.8V, 2.0V when operating at 2.5V, 2.64V when
operating at 3.3V) before voltage is applied to VDDCR. As described in Section 3.7.4.2, when REGOFF is left floating
or connected to VSS, the internal regulator is enabled and the system is not required to supply +1.2V to the VDDCR pin.
3.7.3.2
Enabling the Internal +1.2V Regulator
The +1.2V for VDDCR is supplied by the on-chip regulator unless the transceiver is configured for the regulator off mode
using the REGOFF configuration strap as described in Section 3.7.4.1. By default, the internal +1.2V regulator is
enabled when REGOFF is floating (due to the internal pull-down resistor). During power-on, if REGOFF is sampled
below VIL, then the internal +1.2V regulator will turn on and operate with power from the VDD2A pin.
3.7.4
NINTSEL: NINT/REFCLKO CONFIGURATION
The nINTSEL configuration strap is used to select between one of two available modes: REF_CLK In Mode (nINT) and
REF_CLK Out Mode. The configured mode determines the function of the nINT/REFCLKO pin. The nINTSEL configuration strap is latched at POR and on the rising edge of the nRST. By default, nINTSEL is configured for nINT mode via
the internal pull-up resistor.
TABLE 3-6:
NINTSEL CONFIGURATION
Strap Value
Mode
nINTSEL = 0
REF_CLK Out Mode
nINTSEL = 1
REF_CLK In Mode
REF_CLK description
nINT/REFCLKO is the source of REF_CLK.
nINT/REFCLKO is an active low interrupt output.
The REF_CLK is sourced externally and must be driven
on the XTAL1/CLKIN pin.
The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_DV, RXD[1:0], TXEN, TXD[1:0]
and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path.
However, on the receive data path, the receiver recovers the clock from the incoming data stream. The device uses
elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK.
In REF_CLK In Mode, the 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. This is the traditional system configuration when using RMII, and is described in Section 3.7.4.1. When configured for REF_CLK Out Mode, the device generates the 50MHz RMII REF_CLK and the nINT interrupt is not available. REF_CLK Out Mode allows a low-cost 25MHz
crystal to be used as the reference for REF_CLK. This configuration may result in reduced system cost and is described
in Section 3.7.4.2.
DS00002165B-page 28
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Note:
Because the nINTSEL configuration strap shares functionality with the LED2 pin, proper consideration must
also be given to the LED polarity. Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on
page 33 for additional information on the relation between nINTSEL and the LED2 polarity.
3.7.4.1
REF_CLK In Mode
In REF_CLK In Mode, the 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. A 50MHz source for REF_CLK must
be available external to the device when using this mode. The clock is driven to both the MAC and PHY as shown in
Figure 3-7.
FIGURE 3-7:
EXTERNAL 50MHZ CLOCK SOURCES THE REF_CLK
MAC
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
MDIO
RMII
MDC
nINT
Accepts external
50MHz clock
Mag
TXD[1:0]
2
TXEN
RXD[1:0]
RJ45
TXP
TXN
RXP
RXN
2
CRS_DV
RXER
REF_CLK
XTAL1/CLKIN
LED[2:1]
All RMII signals are
synchronous to the supplied
clock
2
nRST
XTAL2
Interface
50MHz
Reference
Clock
3.7.4.2
REF_CLK Out Mode
To reduce BOM cost, the device includes a feature to generate the RMII REF_CLK signal from a low-cost, 25MHz fundamental crystal. This type of crystal is inexpensive in comparison to 3rd overtone crystals that would normally be
required for 50MHz. The MAC must be capable of operating with an external clock to take advantage of this feature as
shown in Figure 3-8.
In order to optimize package size and cost, the REFCLKO pin is multiplexed with the nINT pin. In REF_CLK Out mode,
the nINT functionality is disabled to accommodate usage of REFCLKO as a 50MHz clock to the MAC.
Note:
The REF_CLK Out Mode is not part of the RMII Specification. Timing in this mode is not compliant with the
RMII specification. To ensure proper system operation, a timing analysis of the MAC and LAN8720 must be
performed.
2016 Microchip Technology Inc.
DS00002165B-page 29
LAN8720A/LAN8720AI
FIGURE 3-8:
MAC
SOURCING REF_CLK FROM A 25MHZ CRYSTAL
RMII
MDIO
MDC
Capable of
accepting 50MHz
clock
Note: nINT not available in
this configuration
LAN8720A/LAN8720Ai
10/100 PHY
TXD[1:0]
24-QFN
RMII
2
TXEN
RXD[1:0]
2
Mag
RJ45
TXP
TXN
CRS_DV
RXER
REF_CLK
RXP
RXN
REFCLKO
XTAL1/CLKIN
LED[2:1]
25MHz
2
nRST
XTAL2
Interface
In some system architectures, a 25MHz clock source is available. The device can be used to generate the REF_CLK
to the MAC as shown in FIGURE 3-9:. It is important to note that in this specific example, only a 25MHz clock can be
used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the nINT function is disabled.
DS00002165B-page 30
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
FIGURE 3-9:
SOURCING REF_CLK FROM EXTERNAL 25MHZ SOURCE
Note: nINT is not available in
this configuration
MAC
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
MDIO
RMII
MDC
Capable of
accepting 50MHz
clock
TXD[1:0]
2
TXEN
Mag
RJ45
TXP
TXN
RXD[1:0]
RXP
2
CRS_DV
RXN
RXER
REF_CLK
REFCLKO
XTAL1/CLKIN
LED[2:1]
25MHz
Clock
2
nRST
XTAL2
Interface
3.8
3.8.1
Miscellaneous Functions
LEDS
Two LED signals are provided as a convenient means to determine the transceiver's mode of operation. All LED signals
are either active high or active low as described in Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection" and Section
3.8.1.1, "REGOFF and LED1 Polarity Selection," on page 33.
The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is active (high) indicating activity.
The LED2 output is driven active when the operating speed is 100Mbps. This LED will go inactive when the operating
speed is 10Mbps or during line isolation.
Note:
When pulling the LED1 and LED2 pins high, they must be tied to VDD2A, NOT VDDIO.
2016 Microchip Technology Inc.
DS00002165B-page 31
LAN8720A/LAN8720AI
3.8.1.1
REGOFF and LED1 Polarity Selection
The REGOFF configuration strap is shared with the LED1 pin. The LED1 output will automatically change polarity based
on the presence of an external pull-up resistor. If the LED1 pin is pulled high to VDD2A by an external pull-up resistor
to select a logical high for REGOFF, then the LED1 output will be active low. If the LED1 pin is pulled low by the internal
pull-down resistor to select a logical low for REGOFF, the LED1 output will then be an active high output. Figure 3-7
details the LED1 polarity for each REGOFF configuration.
FIGURE 3-10:
LED1/REGOFF POLARITY CONFIGURATION
REGOFF = 1 (Regulator OFF)
LED output = Active Low
REGOFF = 0 (Regulator ON)
LED output = Active High
VDD2A
LED1/REGOFF
10K
~270 ohms
~270 ohms
LED1/REGOFF
Note:
3.8.1.2
Refer to Section 3.7.4, "REGOFF: Internal +1.2V Regulator Configuration," on page 32 for additional information on the REGOFF configuration strap.
nINTSEL and LED2 Polarity Selection
The nINTSEL configuration strap is shared with the LED2 pin. The LED2 output will automatically change polarity based
on the presence of an external pull-down resistor. If the LED2 pin is pulled high to VDD2A to select a logical high for
nINTSEL, then the LED2 output will be active low. If the LED2 pin is pulled low by an external pull-down resistor to select
a logical low for nINTSEL, the LED2 output will then be an active high output. Figure 3-8 details the LED2 polarity for
each nINTSEL configuration.
FIGURE 3-11:
LED2/NINTSEL POLARITY CONFIGURATION
nINTSEL = 1
LED output = Active Low
nINTSEL = 0
LED output = Active High
VDD2A
LED2/nINTSEL
10K
~270 ohms
~270 ohms
LED2/nINTSEL
Note:
Refer to Section 3.7.5, "nINTSEL: nINT/TXER/TXD4 Configuration," on page 32 for additional information
on the nINTSEL configuration strap.
DS00002165B-page 32
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
3.8.2
VARIABLE VOLTAGE I/O
The device’s digital I/O pins are variable voltage, allowing them to take advantage of low power savings from shrinking
technologies. These pins can operate from a low I/O voltage of +1.62V up to +3.6V. The applied I/O voltage must maintain its value with a tolerance of ± 10%. Varying the voltage up or down after the transceiver has completed power-on
reset can cause errors in the transceiver operation. Refer to Section 5.0, "Operational Characteristics," on page 54 for
additional information.
Note:
3.8.3
Input signals must not be driven high before power is applied to the device.
POWER-DOWN MODES
There are two device power-down modes: General Power-Down Mode and Energy Detect Power-Down Mode. These
modes are described in the following subsections.
3.8.3.1
General Power-Down
This power-down mode is controlled via the Power Down bit of the Basic Control Register. In this mode, the entire transceiver (except the management interface) is powered-down and remains in this mode as long as the Power Down bit is
“1”. When the Power Down bit is cleared, the transceiver powers up and is automatically reset.
3.8.3.2
Energy Detect Power-Down
This power-down mode is activated by setting the EDPWRDOWN bit of the Mode Control/Status Register. In this mode,
when no energy is present on the line the transceiver is powered down (except for the management interface, the
SQUELCH circuit, and the ENERGYON logic). The ENERGYON logic is used to detect the presence of valid energy
from 100BASE-TX, 10BASE-T, or Auto-negotiation signals.
In this mode, when the ENERGYON bit of the Mode Control/Status Register is low, the transceiver is powered-down
and nothing is transmitted. When energy is received via link pulses or packets, the ENERGYON bit goes high and the
transceiver powers-up. The device automatically resets into the state prior to power-down and asserts the nINT interrupt
if the ENERGYON interrupt is enabled in the Interrupt Mask Register. The first and possibly the second packet to activate ENERGYON may be lost.
When the EDPWRDOWN bit of the Mode Control/Status Register is low, energy detect power-down is disabled.
3.8.4
ISOLATE MODE
The device data paths may be electrically isolated from the RMII interface by setting the Isolate bit of the Basic Control
Register to “1”. In isolation mode, the transceiver does not respond to the TXD, TXEN and TXER inputs, but does
respond to management transactions.
Isolation provides a means for multiple transceivers to be connected to the same RMII interface without contention. By
default, the transceiver is not isolated (on power-up (Isolate=0).
3.8.5
RESETS
The device provides two forms of reset: Hardware and Software. The device registers are reset by both Hardware and
Software resets. Select register bits, indicated as “NASR” in the register definitions, are not cleared by a Software reset.
The registers are not reset by the power-down modes described in Section 3.8.3.
Note:
3.8.5.1
For the first 16us after coming out of reset, the RMII interface will run at 2.5 MHz. After this time, it will switch
to 25 MHz if auto-negotiation is enabled.
Hardware Reset
A Hardware reset is asserted by driving the nRST input pin low. When driven, nRST should be held low for the minimum
time detailed in Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page 59 to ensure a proper transceiver reset. During a Hardware reset, an external clock must be supplied to the XTAL1/CLKIN signal.
Note:
3.8.5.2
A hardware reset (nRST assertion) is required following power-up. Refer to Section 5.5.3, "Power-On nRST
& Configuration Strap Timing," on page 59 for additional information.
Software Reset
A Software reset is activated by setting the Soft Reset bit of the Basic Control Register to “1”. All registers bits, except
those indicated as “NASR” in the register definitions, are cleared by a Software reset. The Soft Reset bit is self-clearing.
Per the IEEE 802.3u standard, clause 22 (22.2.4.1.1) the reset process will be completed within 0.5s from the setting
of this bit.
2016 Microchip Technology Inc.
DS00002165B-page 33
LAN8720A/LAN8720AI
3.8.6
CARRIER SENSE
The carrier sense (CRS) is output on the CRS_DV pin. CRS is a signal defined by the MII specification in the IEEE
802.3u standard. The device asserts CRS based only on receive activity whenever the transceiver is either in repeater
mode or full-duplex mode. Otherwise the transceiver asserts CRS based on either transmit or receive activity.
The carrier sense logic uses the encoded, unscrambled data to determine carrier activity status. It activates carrier
sense with the detection of 2 non-contiguous zeros within any 10 bit span. Carrier sense terminates if a span of 10 consecutive ones is detected before a /J/K/ Start-of Stream Delimiter pair. If an SSD pair is detected, carrier sense is
asserted until either /T/R/ End–of-Stream Delimiter pair or a pair of IDLE symbols is detected. Carrier is negated after
the /T/ symbol or the first IDLE. If /T/ is not followed by /R/, then carrier is maintained. Carrier is treated similarly for IDLE
followed by some non-IDLE symbol.
3.8.7
LINK INTEGRITY TEST
The device performs the link integrity test as outlined in the IEEE 802.3u (Clause 24-15) Link Monitor state diagram.
The link status is multiplexed with the 10Mbps link status to form the Link Status bit in the Basic Status Register and to
drive the LINK LED (LED1).
The DSP indicates a valid MLT-3 waveform present on the RXP and RXN signals as defined by the ANSI X3.263 TPPMD standard, to the Link Monitor state-machine, using the internal DATA_VALID signal. When DATA_VALID is
asserted, the control logic moves into a Link-Ready state and waits for an enable from the auto-negotiation block. When
received, the Link-Up state is entered, and the Transmit and Receive logic blocks become active. Should auto-negotiation be disabled, the link integrity logic moves immediately to the Link-Up state when the DATA_VALID is asserted.
To allow the line to stabilize, the link integrity logic will wait a minimum of 330 sec from the time DATA_VALID is
asserted until the Link-Ready state is entered. Should the DATA_VALID input be negated at any time, this logic will
immediately negate the Link signal and enter the Link-Down state.
When the 10/100 digital block is in 10BASE-T mode, the link status is derived from the 10BASE-T receiver logic.
3.8.8
LOOPBACK OPERATION
The device may be configured for near-end loopback and far loopback. These loopback modes are detailed in the following subsections.
3.8.8.1
Near-end Loopback
Near-end loopback mode sends the digital transmit data back out the receive data signals for testing purposes, as indicated by the blue arrows in Figure 3-9. The near-end loopback mode is enabled by setting the Loopback bit of the Basic
Control Register to “1”. A large percentage of the digital circuitry is operational in near-end loopback mode because data
is routed through the PCS and PMA layers into the PMD sublayer before it is looped back. The transmitters are powered
down regardless of the state of TXEN.
FIGURE 3-12:
10/100
Ethernet
MAC
NEAR-END LOOPBACK BLOCK DIAGRAM
TXD
X
RXD
Digital
Analog
X
TX
RX
XFMR
CAT-5
SMSC
Ethernet Transceiver
DS00002165B-page 34
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
3.8.8.2
Far Loopback
Far loopback is a special test mode for MDI (analog) loopback as indicated by the blue arrows in Figure 3-11. The far
loopback mode is enabled by setting the FARLOOPBACK bit of the Mode Control/Status Register to “1”. In this mode,
data that is received from the link partner on the MDI is looped back out to the link partner. The digital interface signals
on the local MAC interface are isolated.
FIGURE 3-13:
FAR LOOPBACK BLOCK DIAGRAM
Far-end system
10/100
Ethernet
MAC
TXD
RXD
TX
X
X
RX
Digital
XFMR
Link
Partner
CAT-5
Analog
SMSC
Ethernet Transceiver
3.8.8.3
Connector Loopback
The device maintains reliable transmission over very short cables, and can be tested in a connector loopback as shown
in Figure 3-11. An RJ45 loopback cable can be used to route the transmit signals an the output of the transformer back
to the receiver inputs, and this loopback will work at both 10 and 100.
FIGURE 3-14:
10/100
Ethernet
MAC
CONNECTOR LOOPBACK BLOCK DIAGRAM
TXD
TX
RXD
RX
Digital
Analog
SMSC
Ethernet Transceiver
3.9
XFMR
1
2
3
4
5
6
7
8
RJ45 Loopback Cable.
Created by connecting pin 1 to pin 3
and connecting pin 2 to pin 6.
Application Diagrams
This section provides typical application diagrams for the following:
•
•
•
•
•
Simplified System Level Application Diagram
Power Supply Diagram (1.2V Supplied by Internal Regulator)
Power Supply Diagram (1.2V Supplied by External Source)
Twisted-Pair Interface Diagram (Single Power Supply)
Twisted-Pair Interface Diagram (Dual Power Supplies)
2016 Microchip Technology Inc.
DS00002165B-page 35
LAN8720A/LAN8720AI
3.9.1
SIMPLIFIED SYSTEM LEVEL APPLICATION DIAGRAM
FIGURE 3-15:
SIMPLIFIED SYSTEM LEVEL APPLICATION DIAGRAM
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
MDIO
RMII
MDC
nINT
Mag
RJ45
TXP
TXD[1:0]
2
TXEN
TXN
RXP
RXN
RXD[1:0]
2
RXER
XTAL1/CLKIN
LED[2:1]
25MHz
2
nRST
XTAL2
Interface
DS00002165B-page 36
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
3.9.2
POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY INTERNAL REGULATOR)
FIGURE 3-16:
POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY INTERNAL REGULATOR)
LAN8720A/LAN8720Ai
24-QFN
Ch.2 3.3V
Circuitry
Core Logic
VDDCR
OUT
470 pF
1 uF
VDDDIO
Supply
1.8 - 3.3V
Internal
Regulator
IN
VDD2A
CBYPASS
Ch.1 3.3V
Circuitry
VDDIO
CF
Power
Supply
3.3V
VDD1A
CBYPASS
CBYPASS
RBIAS
LED1/
REGOFF
VSS
12.1k
~270 Ohm
2016 Microchip Technology Inc.
DS00002165B-page 37
LAN8720A/LAN8720AI
3.9.3
POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY EXTERNAL SOURCE)
FIGURE 3-17:
POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY EXTERNAL SOURCE)
LAN8720A/LAN8720Ai
24-QFN
Ch.2 3.3V
Circuitry
Core Logic
VDDCR
Supply
1.2V
VDDCR
OUT
470 pF
1 uF
VDDDIO
Supply
1.8 - 3.3V
Internal
Regulator
VDD2A
IN
(Disabled)
CBYPASS
VDD1A
Ch.1 3.3V
Circuitry
VDDIO
CF
Power
Supply
3.3V
CBYPASS
CBYPASS
RBIAS
LED1/
REGOFF
VSS
12.1k
~270 Ohm
10k
DS00002165B-page 38
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
3.9.4
TWISTED-PAIR INTERFACE DIAGRAM (SINGLE POWER SUPPLY)
FIGURE 3-18:
TWISTED-PAIR INTERFACE DIAGRAM (SINGLE POWER SUPPLY)
LAN8720A/LAN8720Ai
24-QFN
Power
Supply
3.3V
Ferrite
bead
49.9 Ohm Resistors
VDD2A
CBYPASS
VDD1A
CBYPASS
Magnetics
RJ45
TXP
1
2
3
4
5
6
7
8
75
TXN
RXP
75
RXN
1000 pF
3 kV
CBYPASS
2016 Microchip Technology Inc.
DS00002165B-page 39
LAN8720A/LAN8720AI
3.9.5
TWISTED-PAIR INTERFACE DIAGRAM (DUAL POWER SUPPLIES)
FIGURE 3-19:
TWISTED-PAIR INTERFACE DIAGRAM (DUAL POWER SUPPLIES)
LAN8720A/LAN8720Ai
24-QFN
Power
Supply
3.3V
Power
Supply
2.5V - 3.3V
49.9 Ohm Resistors
VDD2A
CBYPASS
VDD1A
CBYPASS
Magnetics
RJ45
TXP
1
2
3
4
5
6
7
8
75
TXN
RXP
75
RXN
1000 pF
3 kV
CBYPASS
DS00002165B-page 40
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
4.0
REGISTER DESCRIPTIONS
This chapter describes the various control and status registers (CSRs). All registers follow the IEEE 802.3 (clause
22.2.4) management register set. All functionality and bit definitions comply with these standards. The IEEE 802.3 specified register index (in decimal) is included with each register definition, allowing for addressing of these registers via
the Serial Management Interface (SMI) protocol.
4.1
Register Nomenclature
Table 4-1 describes the register bit attribute notation used throughout this document.
TABLE 4-1:
REGISTER BIT TYPES
Register Bit Type
Notation
Register Bit Description
R
Read: A register or bit with this attribute can be read.
W
Read: A register or bit with this attribute can be written.
RO
Read only: Read only. Writes have no effect.
WO
Write only: If a register or bit is write-only, reads will return unspecified data.
WC
Write One to Clear: writing a one clears the value. Writing a zero has no effect
WAC
Write Anything to Clear: writing anything clears the value.
RC
Read to Clear: Contents is cleared after the read. Writes have no effect.
LL
Latch Low: Clear on read of register.
LH
Latch High: Clear on read of register.
SC
Self-Clearing: Contents are self-cleared after the being set. Writes of zero have no
effect. Contents can be read.
SS
Self-Setting: Contents are self-setting after being cleared. Writes of one have no
effect. Contents can be read.
RO/LH
Read Only, Latch High: Bits with this attribute will stay high until the bit is read. After it
is read, the bit will either remain high if the high condition remains, or will go low if the
high condition has been removed. If the bit has not been read, the bit will remain high
regardless of a change to the high condition. This mode is used in some Ethernet PHY
registers.
NASR
Not Affected by Software Reset. The state of NASR bits do not change on assertion
of a software reset.
RESERVED
Reserved Field: Reserved fields must be written with zeros to ensure future compatibility. The value of reserved bits is not guaranteed on a read.
Many of these register bit notations can be combined. Some examples of this are shown below:
• R/W: Can be written. Will return current setting on a read.
• R/WAC: Will return current setting on a read. Writing anything clears the bit.
4.2
Control and Status Registers
Table 4-2 provides a list of supported registers. Register details, including bit definitions, are provided in the proceeding
subsections.
2016 Microchip Technology Inc.
DS00002165B-page 41
LAN8720A/LAN8720AI
TABLE 4-2:
SMI REGISTER MAP
Register Index
(Decimal)
4.2.1
Register Name
Group
0
Basic Control Register
Basic
1
Basic Status Register
Basic
2
PHY Identifier 1
Extended
3
PHY Identifier 2
Extended
4
Auto-Negotiation Advertisement Register
Extended
5
Auto-Negotiation Link Partner Ability Register
Extended
6
Auto-Negotiation Expansion Register
Extended
17
Mode Control/Status Register
Vendor-specific
18
Special Modes
Vendor-specific
26
Symbol Error Counter Register
Vendor-specific
27
Control / Status Indication Register
Vendor-specific
29
Interrupt Source Register
Vendor-specific
30
Interrupt Mask Register
Vendor-specific
31
PHY Special Control/Status Register
Vendor-specific
BASIC CONTROL REGISTER
Index (In Decimal):
Bits
0
Size:
16 bits
Description
Type
Default
15
Soft Reset
1 = software reset. Bit is self-clearing. When setting this bit do not set other
bits in this register. The configuration (as described in Section 3.7.2,
MODE[2:0]: Mode Configuration) is set from the register bit values, and not
from the mode pins.
R/W
SC
0b
14
Loopback
0 = normal operation
1 = loopback mode
R/W
0b
13
Speed Select
0 = 10Mbps
1 = 100Mbps
Ignored if Auto-negotiation is enabled (0.12 = 1).
R/W
Note 4-1
12
Auto-Negotiation Enable
0 = disable auto-negotiate process
1 = enable auto-negotiate process (overrides 0.13 and 0.8)
R/W
Note 4-1
DS00002165B-page 42
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Bits
Description
Type
Default
11
Power Down
0 = normal operation
1 = General power down mode
The Auto-Negotiation Enable must be cleared before setting the Power
Down.
R/W
0b
10
Isolate
0 = normal operation
1 = electrical isolation of PHY from the RMII
R/W
0b
9
Restart Auto-Negotiate
0 = normal operation
1 = restart auto-negotiate process
Bit is self-clearing.
R/W
SC
0b
8
Duplex Mode
0 = half duplex
1 = full duplex
Ignored if Auto-Negotiation is enabled (0.12 = 1).
R/W
Note 4-1
RESERVED
RO
—
7:0
Note 4-1
4.2.2
The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
BASIC STATUS REGISTER
Index (In Decimal):
Bits
1
Size:
Description
16 bits
Type
Default
15
100BASE-T4
0 = no T4 ability
1 = T4 able
RO
0b
14
100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
RO
1b
13
100BASE-TX Half Duplex
0 = no TX half duplex ability
1 = TX with half duplex
RO
1b
12
10BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
RO
1b
11
10BASE-T Half Duplex
0 = no 10Mbps with half duplex ability
1 = 10Mbps with half duplex
RO
1b
10
100BASE-T2 Full Duplex
0 = PHY not able to perform full duplex 100BASE-T2
1 = PHY able to perform full duplex 100BASE-T2
RO
0b
2016 Microchip Technology Inc.
DS00002165B-page 43
LAN8720A/LAN8720AI
Bits
Description
Type
Default
9
100BASE-T2 Half Duplex
0 = PHY not able to perform half duplex 100BASE-T2
1 = PHY able to perform half duplex 100BASE-T2
RO
0b
8
Extended Status
0 = no extended status information in register 15
1 = extended status information in register 15
RO
0b
RESERVED
RO
—
5
Auto-Negotiate Complete
0 = auto-negotiate process not completed
1 = auto-negotiate process completed
RO
0b
4
Remote Fault
1 = remote fault condition detected
0 = no remote fault
RO/LH
0b
3
Auto-Negotiate Ability
0 = unable to perform auto-negotiation function
1 = able to perform auto-negotiation function
RO
1b
2
Link Status
0 = link is down
1 = link is up
RO/LL
0b
1
Jabber Detect
0 = no jabber condition detected
1 = jabber condition detected
RO/LH
0b
0
Extended Capabilities
0 = does not support extended capabilities registers
1 = supports extended capabilities registers
RO
1b
7:6
4.2.3
PHY IDENTIFIER 1 REGISTER
Index (In Decimal):
2
Size:
16 bits
Bits
Description
Type
Default
15:0
PHY ID Number
Assigned to the 3rd through 18th bits of the Organizationally Unique Identifier
(OUI), respectively.
R/W
0007h
4.2.4
PHY IDENTIFIER 2 REGISTER
Index (In Decimal):
DS00002165B-page 44
3
Size:
16 bits
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Bits
Type
Default
PHY ID Number
Assigned to the 19th through 24th bits of the OUI.
R/W
110000b
9:4
Model Number
Six-bit manufacturer’s model number.
R/W
001111b
3:0
Revision Number
Four-bit manufacturer’s revision number.
R/W
Note 4-2
15:10
Note 4-2
4.2.5
Description
The default value of this field will vary dependent on the silicon revision number.
AUTO NEGOTIATION ADVERTISEMENT REGISTER
Index (In Decimal):
Bits
4
Size:
16 bits
Type
Default
RESERVED
RO
—
13
Remote Fault
0 = no remote fault
1 = remote fault detected
R/W
0b
12
RESERVED
RO
—
Pause Operation
00 = No PAUSE
01 = Symmetric PAUSE
10 = Asymmetric PAUSE toward link partner
11 = Advertise support for both Symmetric PAUSE and Asymmetric PAUSE
toward local device
R/W
00b
15:14
11:10
Description
Note:
When both Symmetric PAUSE and Asymmetric PAUSE are set,
the device will only be configured to, at most, one of the two settings upon auto-negotiation completion.
9
RESERVED
RO
—
8
100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
R/W
Note 4-3
7
100BASE-TX
0 = no TX ability
1 = TX able
R/W
1b
6
10BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
R/W
Note 4-3
5
10BASE-T
0 = no 10Mbps ability
1 = 10Mbps able
R/W
Note 4-3
2016 Microchip Technology Inc.
DS00002165B-page 45
LAN8720A/LAN8720AI
Bits
4:0
Note 4-3
4.2.6
Description
Selector Field
00001 = IEEE 802.3
Default
R/W
00001b
The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
AUTO NEGOTIATION LINK PARTNER ABILITY REGISTER
Index (In Decimal):
Bits
15
Type
5
Size:
Description
Next Page
0 = no next page ability
1 = next page capable
Note:
16 bits
Type
Default
RO
0b
This device does not support next page ability.
14
Acknowledge
0 = link code word not yet received
1 = link code word received from partner
RO
0b
13
Remote Fault
0 = no remote fault
1 = remote fault detected
RO
0b
RESERVED
RO
—
10
Pause Operation
0 = No PAUSE supported by partner station
1 = PAUSE supported by partner station
RO
0b
9
100BASE-T4
0 = no T4 ability
1 = T4 able
RO
0b
12:11
Note:
This device does not support T4 ability.
8
100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
RO
0b
7
100BASE-TX
0 = no TX ability
1 = TX able
RO
0b
6
10BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
RO
0b
5
10BASE-T
0 = no 10Mbps ability
1 = 10Mbps able
RO
0b
4:0
Selector Field
00001 = IEEE 802.3
RO
00001b
DS00002165B-page 46
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
4.2.7
AUTO NEGOTIATION EXPANSION REGISTER
Index (In Decimal):
Bits
15:5
6
Size:
16 bits
Description
RESERVED
Type
Default
RO
—
4
Parallel Detection Fault
0 = no fault detected by parallel detection logic
1 = fault detected by parallel detection logic
RO/LH
0b
3
Link Partner Next Page Able
0 = link partner does not have next page ability
1 = link partner has next page ability
RO
0b
2
Next Page Able
0 = local device does not have next page ability
1 = local device has next page ability
RO
0b
1
Page Received
0 = new page not yet received
1 = new page received
RO/LH
0b
0
Link Partner Auto-Negotiation Able
0 = link partner does not have auto-negotiation ability
1 = link partner has auto-negotiation ability
RO
0b
Type
Default
RESERVED
RO
—
EDPWRDOWN
Enable the Energy Detect Power-Down mode:
0 = Energy Detect Power-Down is disabled
1 = Energy Detect Power-Down is enabled
R/W
0b
RESERVED
RO
—
FARLOOPBACK
Enables far loopback mode (for example, all the received packets are sent
back simultaneously (in 100BASE-TX only)). This mode works even if the Isolate bit (0.10) is set.
R/W
0b
4.2.8
MODE CONTROL/STATUS REGISTER
Index (In Decimal):
Bits
15:14
13
12:10
9
17
Size:
16 bits
Description
0 = Far loopback mode is disabled
1 = Far loopback mode is enabled
Refer to Section 3.8.9.2, Far Loopback for additional information.
2016 Microchip Technology Inc.
DS00002165B-page 47
LAN8720A/LAN8720AI
Bits
Type
Default
RESERVED
RO
—
ALTINT
Alternate Interrupt Mode:
0 = Primary interrupt system enabled (Default)
1 = Alternate interrupt system enabled
Refer to Section 3.6, Interrupt Management for additional information.
R/W
0b
RESERVED
RO
—
1
ENERGYON
Indicates whether energy is detected. This bit transitions to “0” if no valid
energy is detected within 256ms. It is reset to “1” by a hardware reset and is
unaffected by a software reset. Refer to Section 3.8.3.2, Energy Detect
Power-Down for additional information.
RO
1b
0
RESERVED
R/W
0b
Type
Default
RO
—
R/W
NASR
1b
RO
—
8:7
6
5:2
4.2.9
Description
SPECIAL MODES REGISTER
Index (In Decimal):
Bits
18
Size:
16 bits
Description
15
RESERVED
14
RESERVED
Write as 1, ignore on read.
13:8
RESERVED
7:5
MODE
Transceiver mode of operation. Refer to Section 3.7.2, MODE[2:0]: Mode
Configuration for additional details.
R/W
NASR
Note 4-5
4:0
PHYAD
PHY Address. The PHY Address is used for the SMI address and for initialization of the Cipher (Scrambler) key. Refer to Section 3.7.1, PHYAD[2:0]:
PHY Address Configuration for additional details.
R/W
NASR
Note 4-6
Note 4-4
The default value of this field is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
Note 4-5
The default value of this field is determined by the PHYAD[0] configuration strap. Refer to
Section 3.7.1, PHYAD[2:0]: PHY Address Configuration for additional information.
4.2.10
SYMBOL ERROR COUNTER REGISTER
Index (In Decimal):
DS00002165B-page 48
26
Size:
16 bits
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Bits
Description
Type
Default
15:0
SYM_ERR_CNT
The symbol error counter increments whenever an invalid code symbol is
received (including IDLE symbols) in 100BASE-TX mode. The counter is
incremented only once per packet, even when the received packet contains
more than one symbol error. This counter increments up to 65,536 (216) and
rolls over to 0 after reaching the maximum value.
RO
0000h
Type
Default
Note:
4.2.11
This register is cleared on reset, but is not cleared by reading the
register. This register does not increment in 10BASE-T mode.
SPECIAL CONTROL/STATUS INDICATIONS REGISTER
Index (In Decimal):
Bits
27
Size:
16 bits
Description
15
AMDIXCTRL
HP Auto-MDIX control:
0 = Enable Auto-MDIX
1 = Disable Auto-MDIX (use 27.13 to control channel)
R/W
0b
14
RESERVED
RO
—
13
CH_SELECT
Manual channel select:
0 = MDI (TX transmits, RX receives)
1 = MDIX (TX receives, RX transmits)
R/W
0b
12
RESERVED
RO
—
11
SQEOFF
Disable the SQE test (Heartbeat):
0 = SQE test is enabled
1 = SQE test is disabled
R/W
NASR
0b
RESERVED
RO
—
XPOL
Polarity state of the 10BASE-T:
0 = Normal polarity
1 = Reversed polarity
RO
0b
RESERVED
RO
—
10:5
4
3:0
4.2.12
INTERRUPT SOURCE FLAG REGISTER
Index (In Decimal):
2016 Microchip Technology Inc.
29
Size:
16 bits
DS00002165B-page 49
LAN8720A/LAN8720AI
Bits
15:8
Description
RESERVED
Type
Default
RO
—
7
INT7
0 = not source of interrupt
1 = ENERGYON generated
RO/LH
0b
6
INT6
0 = not source of interrupt
1 = Auto-Negotiation complete
RO/LH
0b
5
INT5
0 = not source of interrupt
1 = Remote Fault Detected
RO/LH
0b
4
INT4
0 = not source of interrupt
1 = Link Down (link status negated)
RO/LH
0b
3
INT3
0 = not source of interrupt
1 = Auto-Negotiation LP Acknowledge
RO/LH
0b
2
INT2
0 = not source of interrupt
1 = Parallel Detection Fault
RO/LH
0b
1
INT1
0 = not source of interrupt
1 = Auto-Negotiation Page Received
RO/LH
0b
0
RESERVED
RO
0b
Type
Default
4.2.13
INTERRUPT MASK REGISTER
Index (In Decimal):
Bits
30
Size:
16 bits
Description
15:8
RESERVED
RO
—
7:1
Mask Bits
0 = interrupt source is masked
1 = interrupt source is enabled
R/W
0000000b
RO
—
Note:
0
Refer to Section 4.2.12, Interrupt Source Flag Register for details
on the corresponding interrupt definitions.
RESERVED
DS00002165B-page 50
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
4.2.14
PHY SPECIAL CONTROL/STATUS REGISTER
Index (In Decimal):
31
Bits
Size:
Type
Default
RESERVED
RO
—
Autodone
Auto-negotiation done indication:
0 = Auto-negotiation is not done or disabled (or not active)
1 = Auto-negotiation is done
RO
0b
11:5
RESERVED - Write as 0000010b, ignore on read.
R/W
0000010b
4:2
Speed Indication
HCDSPEED value:
001 = 10BASE-T half-duplex
101 = 10BASE-T full-duplex
010 = 100BASE-TX half-duplex
110 = 100BASE-TX full-duplex
RO
XXX
1:0
RESERVED
RO
—
15:13
12
Description
16 bits
2016 Microchip Technology Inc.
DS00002165B-page 51
LAN8720A/LAN8720AI
5.0
OPERATIONAL CHARACTERISTICS
5.1
Absolute Maximum Ratings*
Supply Voltage (VDDIO, VDD1A, VDD2A) (Note 5-1) ............................................................................... -0.5V to +3.6V
Digital Core Supply Voltage (VDDCR) (Note 5-1) ...................................................................................... -0.5V to +1.5V
Ethernet Magnetics Supply Voltage ........................................................................................................... -0.5V to +3.6V
Positive voltage on signal pins, with respect to ground (Note 5-2)..............................................................................+6V
Negative voltage on signal pins, with respect to ground (Note 5-3) ......................................................................... -0.5V
Positive voltage on XTAL1/CLKIN, with respect to ground ......................................................................................+3.6V
Positive voltage on XTAL2, with respect to ground ..................................................................................................+2.5V
Ambient Operating Temperature in Still Air (TA) ............................................................................................... Note 5-40
Storage Temperature............................................................................................................................. .-55oC to +150oC
Junction to Ambient (JA) ................................................................................................................................. .59.8oC/W
Junction to Case (JC)...................................................................................................................................... .12.6oC/W
Lead Temperature Range ........................................................................................... Refer to JEDEC Spec. J-STD-020
HBM ESD Performance per JEDEC JESD22-A114............................................................................................Class 3A
IEC61000-4-2 Contact Discharge ESD Performance (Note 5-5) ............................................................................+/-8kV
IEC61000-4-2 Air-Gap Discharge ESD Performance (Note 5-5) ..........................................................................+/-15kV
Latch-up Performance per EIA/JESD 78.......................................................................................................... .+/-150mA
Note 5-1
When powering this device from laboratory or system power supplies, it is important that the absolute
maximum ratings not be exceeded or device failure can result. Some power supplies exhibit voltage
spikes on their outputs when AC power is switched on or off. In addition, voltage transients on the
AC power line may appear on the DC output. If this possibility exists, it is suggested that a clamp
circuit be used.
Note 5-2
This rating does not apply to the following pins: XTAL1/CLKIN, XTAL2, RBIAS.
Note 5-3
This rating does not apply to the following pins: RBIAS.
Note 5-4
0oC to +85oC for extended commercial version, -40oC to +85oC for industrial version.
Note 5-5
Performed by independent 3rd party test facility.
*Stresses exceeding those listed in this section could cause permanent damage to the device. This is a stress rating
only. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Functional
operation of the device at any condition exceeding those indicated in Section 5.2, "Operating Conditions**", Section 5.1,
"Absolute Maximum Ratings*", or any other applicable section of this specification is not implied. Note, device signals
are NOT 5 volt tolerant unless specified otherwise.
5.2
Operating Conditions**
Supply Voltage (VDDIO).......................................................................................................................... +1.62V to +3.6V
Analog Port Supply Voltage (VDD1A, VDD2A) ......................................................................................... +3.0V to +3.6V
Digital Core Supply Voltage (VDDCR) .................................................................................................. +1.08V to +1.32V
Ethernet Magnetics Supply Voltage ........................................................................................................ +2.25V to +3.6V
Ambient Operating Temperature in Still Air (TA) ................................................................................................. Note 5-4
**Proper operation of the device is guaranteed only within the ranges specified in this section. After the device has completed power-up, VDDIO and the magnetics power supply must maintain their voltage level with +/-10%. Varying the
voltage greater than +/-10% after the device has completed power-up can cause errors in device operation.
Note:
Do not drive input signals without power supplied to the device.
DS00002165B-page 52
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
5.3
Power Consumption
This section details the device power measurements taken over various operating conditions. Unless otherwise noted,
all measurements were taken with power supplies at nominal values (VDDIO, VDD1A, VDD2A = 3.3V, VDDCR = 1.2V).
See Section 3.8.3, Power-Down Modes for a description of the power down modes. For more information on the REF_CLK modes, see Section 3.7.4, nINTSEL: nINT/REFCLKO Configuration.
5.3.1
REF_CLK IN MODE
TABLE 5-1:
DEVICE ONLY CURRENT CONSUMPTION AND POWER DISSIPATION (REF_CLK IN
MODE)
VDDA3.3
Power
PinS(mA)
VDDCR
Power
pin(mA)
VDDIO
power
pin(mA)
Total
Current
(mA)
Total
Power
(mW)
Max
28
21
0.6
49
159
Typical
26
19
0.5
45
148
Min
23
18
0.3
41
96
Note 5-8
Max
9.7
13
0.6
24
77
Typical
8.9
12
0.5
22
70
Min
8.3
12
0.3
20
42
Note 5-8
Max
4.2
3.0
0.2
7.4
25
Typical
4.1
1.9
0.2
6.2
21
Min
3.9
1.9
0
5.8
16
Note 5-8
Max
0.4
2.8
0.2
3.4
11.2
Typical
0.3
1.8
0.2
2.3
7.6
Min
0.3
1.7
0
2
3.0
Note 5-8
Power Pin Group
100BASE-TX /w traffic
10BASE-T /w traffic
Energy Detect Power Down
General Power Down
Note 5-6
The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A,
or from an external 1.2V supply when the internal regulator is disabled.
Note 5-7
Current measurements do not include power applied to the magnetics or the optional external LEDs.
The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T
mode, independent of the 2.5V or 3.3V supply rail of the transformer.
Note 5-8
Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled.
2016 Microchip Technology Inc.
DS00002165B-page 53
LAN8720A/LAN8720AI
5.3.2
REF_CLK OUT MODE
.
TABLE 5-2:
DEVICE ONLY CURRENT CONSUMPTION AND POWER DISSIPATION (REF_CLK
OUT MODE)
VDDA3.3
Power
Pins(mA)
VDDCR
Power
Pin(mA)
VDDIO
Power
Pin(mA)
Total
Current
(mA)
Total
Power
(mW)
Max
28
20
6.3
54
179
Typical
26
19
5.8
50
164
Min
22
15
2.9
39
93
Note 5-11
Max
9.9
13
6.4
30
96
Typical
8.8
12
5.6
26
85
Min
7.1
10
3.0
20
41
Note 5-11
Max
4.5
2.7
0.3
7.5
25
Typical
4.0
1.5
0.2
5.7
19
Min
3.9
1.2
0
5.1
15
Note 5-11
Max
0.4
2.5
0.2
3.1
10.2
Typical
0.4
1.3
0.2
1.9
6.3
Min
0.4
1.0
0
1.4
2.5
Note 5-11
Power Pin Group
100BASE-T /w traffic
10BASE-T /w traffic
Energy Detect Power Down
General Power Down
Note 5-9
The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A,
or from an external 1.2V supply when the internal regulator is disabled.
Note 5-10
Current measurements do not include power applied to the magnetics or the optional external LEDs.
The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T
mode, independent of the 2.5V or 3.3V supply rail of the transformer.
Note 5-11
Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled.
DS00002165B-page 54
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
5.4
DC Specifications
TABLE 5-2: details the non-variable I/O buffer characteristics. These buffer types do not support variable voltage operation. TABLE 5-3: details the variable voltage I/O buffer characteristics. Typical values are provided for 1.8V, 2.5V, and
3.3V VDDIO cases.
TABLE 5-3:
NON-VARIABLE I/O BUFFER CHARACTERISTICS
Parameter
Symbol
Min
Low Input Level
VILI
-0.3
High Input Level
VIHI
Negative-Going Threshold
VILT
1.01
Positive-Going Threshold
VIHT
Schmitt Trigger Hysteresis
(VIHT - VILT)
Typ
Max
Units
Notes
IS Type Input Buffer
V
3.6
V
1.19
1.39
V
Schmitt trigger
1.39
1.59
1.79
V
Schmitt trigger
VHYS
336
399
459
mV
Input Leakage
(VIN = VSS or VDDIO)
IIH
-10
10
uA
Input Capacitance
CIN
2
pF
Low Output Level
VOL
0.4
V
IOL = 12mA
High Output Level
VOH
V
IOH = -12mA
Note 5-9
O12 Type Buffers
VDD2A 0.4
Note 5-10
ICLK Type Buffer
(XTAL1 Input)
Low Input Level
VILI
-0.3
0.35
V
High Input Level
VIHI
0.9
3.6
V
Note 5-12
This specification applies to all inputs and tri-stated bi-directional pins. Internal pull-down and pull-up
resistors add +/- 50uA per-pin (typical).
Note 5-13
XTAL1/CLKIN can optionally be driven from a 25MHz single-ended clock oscillator.
2016 Microchip Technology Inc.
DS00002165B-page 55
LAN8720A/LAN8720AI
TABLE 5-4:
VARIABLE I/O BUFFER CHARACTERISTICS
Parameter
1.8V
Typ
2.5V
Typ
Symbol
Min
Low Input Level
VILI
-0.3
High Input Level
VIHI
Neg-Going Threshold
VILT
0.64
0.83
1.15
Pos-Going Threshold
VIHT
0.81
0.99
Schmitt Trigger Hysteresis (VIHT - VILT)
VHYS
102
158
Input Leakage
(VIN = VSS or VDDIO)
IIH
-10
Input Capacitance
3.3V
Typ
Max
Units
Notes
VIS Type Input Buffer
V
3.6
V
1.41
1.76
V
Schmitt trigger
1.29
1.65
1.90
V
Schmitt trigger
136
138
288
mV
10
uA
CIN
2
pF
Low Output Level
VOL
0.4
V
IOL = 8mA
High Output Level
VOH
V
IOH = -8mA
V
IOL = 8mA
Note 5-11
VO8 Type Buffers
VDDIO 0.4
VOD8 Type Buffer
Low Output Level
Note 5-14
TABLE 5-5:
VOL
0.4
This specification applies to all inputs and tri-stated bi-directional pins. Internal pull-down and pull-up
resistors add +/- 50uA per-pin (typical).
100BASE-TX TRANSCEIVER CHARACTERISTICS
Parameter
Symbol
Min
Typ
Max
Units
Notes
Peak Differential Output Voltage High
VPPH
950
—
1050
mVpk
Note 5-12
Peak Differential Output Voltage Low
VPPL
-950
—
-1050
mVpk
Note 5-12
Signal Amplitude Symmetry
VSS
98
—
102
%
Note 5-12
Signal Rise and Fall Time
TRF
3.0
—
5.0
nS
Note 5-12
Rise and Fall Symmetry
TRFS
—
—
0.5
nS
Note 5-12
Duty Cycle Distortion
DCD
35
50
65
%
Note 5-13
Overshoot and Undershoot
VOS
—
—
5
%
—
—
—
—
1.4
nS
Note 5-14
Jitter
Note 5-15
Measured at line side of transformer, line replaced by 100 (+/- 1%) resistor.
Note 5-16
Offset from 16nS pulse width at 50% of pulse peak.
DS00002165B-page 56
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Note 5-17
TABLE 5-6:
Measured differentially.
10BASE-T TRANSCEIVER CHARACTERISTICS
Parameter
Symbol
Min
Typ
Max
Units
Notes
Transmitter Peak Differential Output Voltage
VOUT
2.2
2.5
2.8
V
Note 5-15
Receiver Differential Squelch Threshold
VDS
300
420
585
mV
—
Note 5-18
5.5
Min/max voltages guaranteed as measured with 100 resistive load.
AC Specifications
This section details the various AC timing specifications of the device.
Note 5-19
The SMI timing adheres to the IEEE 802.3 specification. Refer to the IEEE 802.3 specification for
additional timing information.
Note 5-20
The RMII timing adheres to the RMII Consortium RMII Specification R1.2.
5.5.1
EQUIVALENT TEST LOAD
Output timing specifications assume a 25pF equivalent test load, unless otherwise noted, as illustrated in Figure 5-1
below.
FIGURE 5-1:
OUTPUT EQUIVALENT TEST LOAD
OUTPUT
25 pF
2016 Microchip Technology Inc.
DS00002165B-page 57
LAN8720A/LAN8720AI
5.5.2
POWER SEQUENCE TIMING
This diagram illustrates the device power sequencing requirements. The VDDIO, VDD1A, VDD2A and magnetics power
supplies can turn on in any order provided they all reach operational levels within the specified time period tpon. Device
power supplies can turn off in any order provided they all reach 0 volts within the specified time period poff.
FIGURE 5-2:
POWER SEQUENCE TIMING
tpon
tpoff
VDDIO
Magnetics
Power
VDD1A,
VDD2A
TABLE 5-7:
POWER SEQUENCE TIMING VALUES
Symbol
Min
Typ
Max
Units
tpon
Power supply turn on time
—
—
50
mS
tpoff
Power supply turn off time
—
—
500
mS
Note:
5.5.3
Description
When the internal regulator is disabled, a power-up sequencing relationship exists between VDDCR and
the 3.3V power supply. For additional information refer to Section 3.7.4, REGOFF: Internal +1.2V Regulator Configuration.
POWER-ON NRST & CONFIGURATION STRAP TIMING
This diagram illustrates the nRST reset and configuration strap timing requirements in relation to power-on. A hardware
reset (nRST assertion) is required following power-up. For proper operation, nRST must be asserted for no less than
trstia. The nRST pin can be asserted at any time, but must not be deasserted before tpurstd after all external power supplies have reached 80% of their nominal operating levels. In order for valid configuration strap values to be read at
power-up, the tcss and tcsh timing constraints must be followed. Refer to Section 3.8.5, Resets for additional information.
DS00002165B-page 58
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
FIGURE 5-3:
POWER-ON NRST & CONFIGURATION STRAP TIMING
All External
Power Supplies
80%
tpurstd
tpurstv
trstia
nRST
tcss
tcsh
Configuration Strap
Pins Input
totaa
todad
Configuration Strap
Pins Output Drive
TABLE 5-8:
POWER-ON NRST & CONFIGURATION STRAP TIMING VALUES
symbol
DESCRIPTION
min
typ
max
units
tpurstd
External power supplies at 80% to nRST deassertion
25
—
—
mS
tpurstv
External power supplies at 80% to nRST valid
0
—
—
nS
trstia
nRST input assertion time
100
—
—
S
tcss
Configuration strap pins setup to nRST deassertion
200
—
—
nS
tcsh
Configuration strap pins hold after nRST deassertion
1
—
—
nS
totaa
Output tri-state after nRST assertion
—
50
nS
todad
Output drive after nRST deassertion
—
800
(Note 520)
nS
Note 5-21
nRST deassertion must be monotonic.
Note 5-22
Device configuration straps are latched as a result of nRST assertion. Refer to Section 3.7,
Configuration Straps for details. Configuration straps must only be pulled high or low and must not
be driven as inputs.
Note 5-23
20 clock cycles for 25MHz, or 40 clock cycles for 50MHz.
2016 Microchip Technology Inc.
2
DS00002165B-page 59
LAN8720A/LAN8720AI
5.5.4
RMII INTERFACE TIMING
5.5.4.1
RMII Timing (REF_CLK Out Mode)
The 50MHz REF_CLK OUT timing applies to the case when nINTSEL is pulled-low. In this mode, a 25MHz crystal or
clock oscillator must be input on the XTAL1/CLKIN and XTAL2 pins. For more information on REF_CLK Out Mode, see
Section 3.7.4.2, REF_CLK Out Mode.
FIGURE 5-4:
RMII TIMING (REF_CLK OUT MODE)
tclkp
tclkh tclkl
REFCLKO
toval
RXD[1:0],
RXER
toval
tohold
tohold
toval
CRS_DV
tsu tihold
tsu tihold
tihold
TXD[1:0]
tihold
tsu
TXEN
TABLE 5-9:
RMII TIMING VALUES (REF_CLK OUT MODE)
Symbol
Description
Min
Max
Units
Notes
20
—
ns
—
tclkp
REFCLKO period
tclkh
REFCLKO high time
tclkp*0.4
tclkp*0.6
ns
—
tclkl
REFCLKO low time
tclkp*0.4
tclkp*0.6
ns
—
toval
RXD[1:0], RXER, CRS_DV output valid from rising edge of REFCLKO
—
5.0
ns
Note 5-24
tohold
RXD[1:0], RXER, CRS_DV output hold from rising edge of REFCLKO
1.4
—
ns
Note 5-24
TXD[1:0], TXEN setup time to rising edge of
REFCLKO
7.0
—
ns
Note 5-24
TXD[1:0], TXEN input hold time after rising edge
of REFCLKO
2.0
—
ns
Note 5-24
tsu
tihold
Note 5-24
Timing was designed for system load between 10 pf and 25 pf.
DS00002165B-page 60
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
5.5.4.2
RMII Timing (REF_CLK In Mode)
The 50MHz REF_CLK IN timing applies to the case when nINTSEL is floated or pulled-high. In this mode, a 50MHz
clock must be input on the CLKIN pin. For more information on REF_CLK In Mode, see Section 3.7.4.1, REF_CLK In
Mode.
FIGURE 5-5:
RMII TIMING (REF_CLK IN MODE)
tclkp
tclkh
CLKIN
(REF_CLK)
tclkl
toval
RXD[1:0],
RXER
toval
tohold
tohold
toval
CRS_DV
tsu tihold
tsu tihold
tihold
TXD[1:0]
tihold
tsu
TXEN
TABLE 5-10:
RMII TIMING VALUES (REF_CLK IN MODE)
Symbol
Description
Min
Max
Units
Notes
20
—
ns
—
tclkp
CLKIN period
tclkh
CLKIN high time
tclkp*0.35
tclkp*0.65
ns
—
tclkl
CLKIN low time
tclkp*0.35
tclkp*0.65
ns
—
toval
RXD[1:0], RXER, CRS_DV output valid from rising edge of CLKIN
—
14.0
ns
Note 5-25
tohold
RXD[1:0], RXER, CRS_DV output hold from rising edge of CLKIN
3.0
—
ns
Note 5-25
TXD[1:0], TXEN setup time to rising edge of
CLKIN
4.0
—
ns
Note 5-25
TXD[1:0], TXEN input hold time after rising edge
of CLKIN
1.5
—
ns
Note 5-25
tsu
tihold
Note 5-25
Timing was designed for system load between 10 pf and 25 pf.
2016 Microchip Technology Inc.
DS00002165B-page 61
LAN8720A/LAN8720AI
5.5.4.3
RMII CLKIN Requirements
TABLE 5-11:
RMII CLKIN (REF_CLK) TIMING VALUES
Parameter
Min
Typ
Max
Units
Notes
CLKIN frequency
50
—
MHz
—
CLKIN Frequency Drift
—
± 50
ppm
—
—
60
%
—
—
150
psec
p-p – not RMS
CLKIN Duty Cycle
40
CLKIN Jitter
5.5.5
SMI TIMING
This section specifies the SMI timing of the device. Please refer to Section 3.5, Serial Management Interface (SMI) for
additional details.
FIGURE 5-6:
SMI TIMING
tclkp
tclkh
tclkl
MDC
tval
tohold
tohold
MDIO
(Data-Out)
tsu tihold
MDIO
(Data-In)
TABLE 5-12:
SMI TIMING VALUES
Symbol
Description
Min
Max
Units
Notes
400
—
ns
—
tclkp
MDC period
tclkh
MDC high time
160 (80%)
—
ns
—
tclkl
MDC low time
160 (80%)
—
ns
—
tval
MDIO (read from PHY) output valid from rising
edge of MDC
—
300
ns
—
tohold
MDIO (read from PHY) output hold from rising
edge of MDC
0
—
ns
—
tsu
MDIO (write to PHY) setup time to rising edge of
MDC
10
—
ns
—
tihold
MDIO (write to PHY) input hold time after rising
edge of MDC
10
—
ns
—
DS00002165B-page 62
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
5.6
Clock Circuit
The device can accept either a 25MHz crystal (preferred) or a 25MHz single-ended clock oscillator (±50ppm) input. If
the single-ended clock oscillator method is implemented, XTAL2 should be left unconnected and XTAL1/CLKIN should
be driven with a nominal 0-3.3V clock signal.
It is recommended that a crystal utilizing matching parallel load capacitors be used for the crystal input/output signals
(XTAL1/XTAL2). Either a 300uW or 100uW 25MHz crystal may be utilized. The 300uW 25MHz crystal specifications are
detailed in Section 5.6.1, "300uW 25MHz Crystal Specification," on page 65. The 100uW 25MHz crystal specifications
are detailed in Section 5.6.2, "100uW 25MHz Crystal Specification," on page 66.
5.6.1
300UW 25MHZ CRYSTAL SPECIFICATION
When utilizing a 300uW 25MHz crystal, the following circuit design (Figure 5-8) and specifications (Table 5-12) are
required to ensure proper operation.
FIGURE 5-7:
300UW 25MHZ CRYSTAL CIRCUIT
LAN8720
XTAL2
Y1
XTAL1
C1
TABLE 5-13:
C2
300UW 25MHZ CRYSTAL SPECIFICATIONS
Parameter
Symbol
Min
Nom
Crystal Cut
Max
Units
Notes
AT, typ
—
Crystal Oscillation Mode
Fundamental Mode
—
Crystal Calibration Mode
Parallel Resonant Mode
—
Frequency
Ffund
—
25.000
—
MHz
—
Frequency Tolerance @ 25oC
Ftol
—
—
±50
PPM
Note 5-26
Frequency Stability Over Temp
Ftemp
—
—
±50
PPM
Note 5-26
Frequency Deviation Over Time
Fage
—
+/-3 to 5
—
PPM
Note 5-27
Total Allowable PPM Budget
—
—
—
±50
PPM
Note 5-28
Shunt Capacitance
CO
—
7 typ
—
pF
—
Load Capacitance
CL
—
20 typ
—
pF
—
Drive Level
PW
300
—
—
uW
—
Equivalent Series Resistance
R1
—
—
30
Ohm
—
Operating Temperature Range
—
Note 5-35
—
+85
oC
—
XTAL1/CLKIN Pin Capacitance
—
—
3 typ
—
pF
Note 5-30
XTAL2 Pin Capacitance
—
—
3 typ
—
pF
Note 5-30
2016 Microchip Technology Inc.
DS00002165B-page 63
LAN8720A/LAN8720AI
Note 5-26
The maximum allowable values for Frequency Tolerance and Frequency Stability are application
dependent. Since any particular application must meet the IEEE ±50 PPM Total PPM Budget, the
combination of these two values must be approximately ±45 PPM (allowing for aging).
Note 5-27
Frequency Deviation Over Time is also referred to as Aging.
Note 5-28
The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as
±100 PPM.
Note 5-29
0oC for extended commercial version, -40oC for industrial version.
Note 5-30
This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included
in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are required to
accurately calculate the value of the two external load capacitors. The total load capacitance must
be equivalent to what the crystal expects to see in the circuit so that the crystal oscillator will operate
at 25.000 MHz.
5.6.2
100UW 25MHZ CRYSTAL SPECIFICATION
When utilizing a 100uW 25MHz crystal, the following circuit design (Figure 5-9) and specifications (Table 5-13) are
required to ensure proper operation.
FIGURE 5-8:
100UW 25MHZ CRYSTAL CIRCUIT
LAN8720
XTAL2
RS
Y1
XTAL1
C2
C1
TABLE 5-14:
100UW 25MHZ CRYSTAL SPECIFICATIONS
Parameter
Symbol
Min
Crystal Cut
Nom
Max
Units
Notes
AT, typ
—
Crystal Oscillation Mode
Fundamental Mode
—
Crystal Calibration Mode
Parallel Resonant Mode
—
Frequency
Ffund
—
25.000
—
MHz
—
Ftol
—
—
±50
PPM
Note 5-31
Frequency Stability Over Temp
Ftemp
—
—
±50
PPM
Note 5-31
Frequency Deviation Over Time
Fage
—
±3 to 5
—
PPM
Note 5-32
Total Allowable PPM Budget
—
—
—
±50
PPM
Note 5-33
Shunt Capacitance
CO
—
—
5
pF
—
Load Capacitance
CL
8
—
12
pF
—
Drive Level
PW
—
100
—
uW
Note 5-34
Frequency Tolerance @
DS00002165B-page 64
25oC
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
TABLE 5-14:
100UW 25MHZ CRYSTAL SPECIFICATIONS (CONTINUED)
Parameter
Symbol
Min
Nom
Max
Units
Notes
Equivalent Series Resistance
R1
—
—
80
Ohm
—
XTAL2 Series Resistor
Rs
495
500
505
Ohm
—
Operating Temperature Range
—
Note 5-35
—
+85
oC
—
XTAL1/CLKIN Pin Capacitance
—
—
3 typ
—
pF
Note 5-36
XTAL2 Pin Capacitance
—
—
3 typ
—
pF
Note 5-36
Note 5-31
The maximum allowable values for Frequency Tolerance and Frequency Stability are application
dependent. Since any particular application must meet the IEEE ±50 PPM Total PPM Budget, the
combination of these two values must be approximately ±45 PPM (allowing for aging).
Note 5-32
Frequency Deviation Over Time is also referred to as Aging.
Note 5-33
The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as
±100 PPM.
Note 5-34
The crystal must support 100uW operation to utilize this circuit.
Note 5-35
0oC for extended commercial version, -40oC for industrial version.
Note 5-36
This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included
in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are required to
accurately calculate the value of the two external load capacitors. The total load capacitance must
be equivalent to what the crystal expects to see in the circuit so that the crystal oscillator will operate
at 25.000 MHz.
2016 Microchip Technology Inc.
DS00002165B-page 65
LAN8720A/LAN8720AI
6.0
PACKAGE INFORMATION
6.1
24-QFN (Punch)
A
A1
A2
D/E
D1/E1
D2/E2
L
b
k
e
Note 1:
2:
3:
Min
0.70
0
—
3.90
3.55
2.40
0.30
0.18
0.25
Nominal
0.85
0.02
—
4.00
3.75
2.50
0.40
0.25
—
0.50 BSC
Max
1.00
0.05
0.90
4.10
3.95
2.60
0.50
0.30
—
Remarks
Overall Package Height
Standoff
Mold Cap Thickness
X/Y Body Size
X/Y Mold Cap Size
X/Y Exposed Pad Size
Terminal Length
Terminal Width
Terminal to Exposed Pad Clearance
Terminal Pitch
All dimensions are in millimeters unless otherwise noted.
Dimension “b” applies to plated terminals and is measured between 0.15 and 0.30 mm from the terminal tip.
The pin 1 identifier may vary, but is always located within the zone indicated.
DS00002165B-page 66
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
2016 Microchip Technology Inc.
DS00002165B-page 67
LAN8720A/LAN8720AI
6.2
24-SQFN (Sawn)
DS00002165B-page 68
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
6.3
Note:
Tape & Reel Information
Standard reel size is 5,000 pieces per reel.
2016 Microchip Technology Inc.
DS00002165B-page 69
LAN8720A/LAN8720AI
DS00002165B-page 70
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
7.0
APPLICATION NOTES
7.1
Application Diagram
The device requires few external components. The voltage on the magnetics center tap can range from 2.5 - 3.3V.
7.1.1
RMII DIAGRAM
FIGURE 7-1:
SIMPLIFIED APPLICATION DIAGRAM
RMII
MDIO
MDC
nINT
LAN8720
10/100 PHY
24-QFN
RMII
Mag
RJ45
TXP
TXD[1:0]
2
TXEN
TXN
RXP
RXN
RXD[1:0]
2
RXER
XTAL1/CLKIN
LED[2:1]
25MHz
2
nRST
XTAL2
Interface
7.1.2
POWER SUPPLY DIAGRAM
2016 Microchip Technology Inc.
DS00002165B-page 71
LAN8720A/LAN8720AI
FIGURE 7-3:
HIGH-LEVEL SYSTEM DIAGRAM FOR POWER
Analog
Supply
3.3V
Power to
magnetics
interface.
6
LAN8720
24-QFN
VDDCR
19
VDD1A
1uF
CBYPASS
VDDDIO
Supply
1.8 - 3.3V
9
VDDIO
1
VDD2A
CBYPASS
CBYPASS
CF
R
15
24
RBIAS
nRST
C
12k
VSS
7.1.3
TWISTED-PAIR INTERFACE DIAGRAM
FIGURE 7-5:
COPPER INTERFACE DIAGRAM
LAN8720
24-QFN
Analog
Supply
3.3V
VDD2A
49.9 Resistors
Magnetic
Supply
2.5 - 3.3V
1
CBYPASS
VDD1A
19
CBYPASS
Magnetics
RJ45
TXP
21
1
2
3
4
5
6
7
8
75
TXN
RXP
20
23
75
RXN
22
CBYPASS
DS00002165B-page 72
1000 pF
3 kV
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
APPENDIX A:
TABLE A-1:
DATA SHEET REVISION HISTORY
REVISION HISTORY
Revision
Section/Figure/Entry
Rev B. (07-15-16)
Section 5.1, "Absolute Maximum Ratings*," on page 54
Update to Positive voltage on XTAL1/CLKIN, with
respect to ground.
Table 5-2, “Non-Variable I/O
Buffer Characteristics,” on
page 56
Update to min/max values for the last row, ICLK
Type Buffer (XTAL1 Input) - High Input Level.
All
Document converted to Microchip look and feel.
Replaces SMSC Rev. 1.4 (08-23-12).
Section 5.2, "Operating Conditions**," on page 54
Increased VDDCR operational limits from “+1.14V
to +1.26V” to “+1.08V to +1.32V”
Section 5.6, "Clock Circuit,"
on page 65
Added new 100uW crystal specifications and circuit
diagram. The section is now split into two subsections, one for 300uW crystals and the other for
100uW crystals.
Section 6.0, "Package Information," on page 68
Added new subsections to include SQFN package
information.
Section , "Product Identification System," on page 77
Updated ordering codes with sawn SQFN package
options.
Rev. 1.4
(08-23-12)
Section 4.2.2, Basic Status
Register
Updated definitions of bits 10:8.
Rev. 1.3
(04-20-11)
Table 5-9, “RMII Timing Values (REF_CLK Out Mode),”
on page 60
Updated toval maximum value from 10.0ns to 5.0ns.
Section 5.5.5, "RMII Interface Timing," on page 63
Updated diagrams and tables to include RXER.
Rev. A (06-24-16)
Rev. 1.2 (11-10-10)
2016 Microchip Technology Inc.
Correction
DS00002165B-page 73
LAN8720A/LAN8720AI
THE MICROCHIP WEB SITE
Microchip provides online support via our WWW site at www.microchip.com. This web site is used as a means to make
files and information easily available to customers. Accessible by using your favorite Internet browser, the web site contains the following information:
• Product Support – Data sheets and errata, application notes and sample programs, design resources, user’s
guides and hardware support documents, latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQ), technical support requests, online discussion
groups, Microchip consultant program member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip press releases, listing of seminars and events, listings of Microchip sales offices, distributors and factory representatives
CUSTOMER CHANGE NOTIFICATION SERVICE
Microchip’s customer notification service helps keep customers current on Microchip products. Subscribers will receive
e-mail notification whenever there are changes, updates, revisions or errata related to a specified product family or
development tool of interest.
To register, access the Microchip web site at www.microchip.com. Under “Support”, click on “Customer Change Notification” and follow the registration instructions.
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
•
•
•
•
Distributor or Representative
Local Sales Office
Field Application Engineer (FAE)
Technical Support
Customers should contact their distributor, representative or field application engineer (FAE) for support. Local sales
offices are also available to help customers. A listing of sales offices and locations is included in the back of this document.
Technical support is available through the web site at: http://microchip.com/support
DS00002165B-page 74
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO.
[X]
Device
Temperature
Range
[X](1)
-
Tape & Reel
Option
Device:
LAN8720A
Temperature
Range:
CP
i-CP
=
0C to
= -40C to
Tape and Reel
Option:
Blank
TR
= Standard packaging (tray)
= Tape and Reel(1)
Package:
Blank
ABC
= Punch Package (24-QFN)
= Sawn Package (24-SQFN)
+85C
+85C
-
[XXX]
Package
Examples:
a)
LAN8720Ai-CP-TR
Industrial temp., Tape & Reel, 24-QFN (Punch)
b)
LAN8720A-CP-ABC
Ext. commercial temp., Tray, 24-SQFN (Sawn)
(Extended Commercial)
(Industrial)
Note 1:
2016 Microchip Technology Inc.
Tape and Reel identifier only appears in the
catalog part number description. This
identifier is used for ordering purposes and is
not printed on the device package. Check
with your Microchip Sales Office for package
availability with the Tape and Reel option.
DS00002165B-page 75
LAN8720A/LAN8720AI
NOTES:
DS00002165B-page 76
2016 Microchip Technology Inc.
LAN8720A/LAN8720AI
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device applications and the like is provided only for your convenience and may be
superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO
REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer’s risk, and the buyer agrees to defend, indemnify and hold
harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or
otherwise, under any Microchip intellectual property rights unless otherwise stated.
Trademarks
The Microchip name and logo, the Microchip logo, AnyRate, dsPIC, FlashFlex, flexPWR, Heldo, JukeBlox, KeeLoq, KeeLoq logo,
Kleer, LANCheck, LINK MD, MediaLB, MOST, MOST logo, MPLAB, OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC,
SST, SST Logo, SuperFlash and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other
countries.
ClockWorks, The Embedded Control Solutions Company, ETHERSYNCH, Hyper Speed Control, HyperLight Load, IntelliMOS,
mTouch, Precision Edge, and QUIET-WIRE are registered trademarks of Microchip Technology Incorporated in the U.S.A.
Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut, BodyCom, chipKIT, chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net,
Dynamic Average Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial Programming, ICSP, Inter-Chip Connectivity, JitterBlocker,
KleerNet, KleerNet logo, MiWi, motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach,
Omniscient Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, PureSilicon, RightTouch logo, REAL ICE, Ripple Blocker, Serial
Quad I/O, SQI, SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC, USBCheck, VariSense, ViewSpan, WiperLock, Wireless
DNA, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries.
GestIC is a registered trademarks of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in
other countries.
All other trademarks mentioned herein are property of their respective companies.
© 2016, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
ISBN: 978-1-5224-0780-5
QUALITY MANAGEMENT SYSTEM
CERTIFIED BY DNV
== ISO/TS 16949 ==
2016 Microchip Technology Inc.
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
DS00002165B-page 77
Worldwide Sales and Service
AMERICAS
ASIA/PACIFIC
ASIA/PACIFIC
EUROPE
Corporate Office
2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: 480-792-7200
Fax: 480-792-7277
Technical Support:
http://www.microchip.com/
support
Web Address:
www.microchip.com
Asia Pacific Office
Suites 3707-14, 37th Floor
Tower 6, The Gateway
Harbour City, Kowloon
China - Xiamen
Tel: 86-592-2388138
Fax: 86-592-2388130
Austria - Wels
Tel: 43-7242-2244-39
Fax: 43-7242-2244-393
China - Zhuhai
Tel: 86-756-3210040
Fax: 86-756-3210049
Denmark - Copenhagen
Tel: 45-4450-2828
Fax: 45-4485-2829
India - Bangalore
Tel: 91-80-3090-4444
Fax: 91-80-3090-4123
France - Paris
Tel: 33-1-69-53-63-20
Fax: 33-1-69-30-90-79
India - New Delhi
Tel: 91-11-4160-8631
Fax: 91-11-4160-8632
Germany - Dusseldorf
Tel: 49-2129-3766400
Atlanta
Duluth, GA
Tel: 678-957-9614
Fax: 678-957-1455
Hong Kong
Tel: 852-2943-5100
Fax: 852-2401-3431
Australia - Sydney
Tel: 61-2-9868-6733
Fax: 61-2-9868-6755
China - Beijing
Tel: 86-10-8569-7000
Fax: 86-10-8528-2104
Austin, TX
Tel: 512-257-3370
China - Chengdu
Tel: 86-28-8665-5511
Fax: 86-28-8665-7889
Boston
Westborough, MA
Tel: 774-760-0087
Fax: 774-760-0088
China - Chongqing
Tel: 86-23-8980-9588
Fax: 86-23-8980-9500
Chicago
Itasca, IL
Tel: 630-285-0071
Fax: 630-285-0075
Cleveland
Independence, OH
Tel: 216-447-0464
Fax: 216-447-0643
Dallas
Addison, TX
Tel: 972-818-7423
Fax: 972-818-2924
Detroit
Novi, MI
Tel: 248-848-4000
Houston, TX
Tel: 281-894-5983
Indianapolis
Noblesville, IN
Tel: 317-773-8323
Fax: 317-773-5453
Los Angeles
Mission Viejo, CA
Tel: 949-462-9523
Fax: 949-462-9608
New York, NY
Tel: 631-435-6000
San Jose, CA
Tel: 408-735-9110
Canada - Toronto
Tel: 905-695-1980
Fax: 905-695-2078
China - Dongguan
Tel: 86-769-8702-9880
China - Guangzhou
Tel: 86-20-8755-8029
China - Hangzhou
Tel: 86-571-8792-8115
Fax: 86-571-8792-8116
China - Hong Kong SAR
Tel: 852-2943-5100
Fax: 852-2401-3431
China - Nanjing
Tel: 86-25-8473-2460
Fax: 86-25-8473-2470
China - Qingdao
Tel: 86-532-8502-7355
Fax: 86-532-8502-7205
China - Shanghai
Tel: 86-21-5407-5533
Fax: 86-21-5407-5066
China - Shenyang
Tel: 86-24-2334-2829
Fax: 86-24-2334-2393
China - Shenzhen
Tel: 86-755-8864-2200
Fax: 86-755-8203-1760
India - Pune
Tel: 91-20-3019-1500
Japan - Osaka
Tel: 81-6-6152-7160
Fax: 81-6-6152-9310
Japan - Tokyo
Tel: 81-3-6880- 3770
Fax: 81-3-6880-3771
Korea - Daegu
Tel: 82-53-744-4301
Fax: 82-53-744-4302
Korea - Seoul
Tel: 82-2-554-7200
Fax: 82-2-558-5932 or
82-2-558-5934
Malaysia - Kuala Lumpur
Tel: 60-3-6201-9857
Fax: 60-3-6201-9859
Malaysia - Penang
Tel: 60-4-227-8870
Fax: 60-4-227-4068
Philippines - Manila
Tel: 63-2-634-9065
Fax: 63-2-634-9069
Germany - Karlsruhe
Tel: 49-721-625370
Germany - Munich
Tel: 49-89-627-144-0
Fax: 49-89-627-144-44
Italy - Milan
Tel: 39-0331-742611
Fax: 39-0331-466781
Italy - Venice
Tel: 39-049-7625286
Netherlands - Drunen
Tel: 31-416-690399
Fax: 31-416-690340
Poland - Warsaw
Tel: 48-22-3325737
Spain - Madrid
Tel: 34-91-708-08-90
Fax: 34-91-708-08-91
Sweden - Stockholm
Tel: 46-8-5090-4654
UK - Wokingham
Tel: 44-118-921-5800
Fax: 44-118-921-5820
Singapore
Tel: 65-6334-8870
Fax: 65-6334-8850
Taiwan - Hsin Chu
Tel: 886-3-5778-366
Fax: 886-3-5770-955
Taiwan - Kaohsiung
Tel: 886-7-213-7828
China - Wuhan
Tel: 86-27-5980-5300
Fax: 86-27-5980-5118
Taiwan - Taipei
Tel: 886-2-2508-8600
Fax: 886-2-2508-0102
China - Xian
Tel: 86-29-8833-7252
Fax: 86-29-8833-7256
Thailand - Bangkok
Tel: 66-2-694-1351
Fax: 66-2-694-1350
06/23/16
DS00002165B-page 78
2016 Microchip Technology Inc.
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