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SN65HVD255, SN65HVD256, SN65HVD257
SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
SN65HVD25x Turbo CAN Transceivers for Higher Data Rates and Large Networks
Including Features for Functional Safety
1 Features
3 Description
•
•
This CAN transceiver meets the ISO1189-2 High
Speed CAN (Controller Area Network) Physical Layer
standard. It is designed for data rates in excess of
1 Mbps for CAN in short networks, and enhanced
timing margin and higher data rates in long and
highly-loaded networks. The device provides many
protection features to enhance device and CANnetwork robustness. The SN65HVD257 device adds
additional features, allowing for easy design of
redundant and multitopology networks with fault
indication for higher levels of functional safety in the
CAN system.
1
•
•
•
•
Meets the Requirements of ISO11898-2
Turbo CAN:
– Short and Symmetrical Propagation Delay
Times and Fast Loop Times for Enhanced
Timing Margin
– Higher Data Rates in CAN Networks
I/O Voltage Range Supports 3.3-V and 5-V MCUs
Ideal Passive Behavior When Unpowered
– Bus and Logic Pins are High Impedance (No
Load)
– Power Up and Power Down With Glitch-Free
Operation on Bus
Protection Features
– HBM ESD Protection Exceeds ±12 kV
– Bus Fault Protection –27 V to 40 V
– Undervoltage Protection on Supply Pins
– Driver Dominant Time Out (TXD DTO)
– SN65HVD257: Receiver-Dominant Time Out
(RXD DTO)
– SN65HVD257: FAULT Output Pin
– Thermal Shutdown Protection
Characterized for –40°C to 125°C Operation
Device Information(1)
PART NUMBER
PACKAGE
SN65HVD255
SN65HVD256
SN65HVD257
BODY SIZE (NOM)
SOIC (8)
4.90 mm × 3.91 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Block Diagram
NC / VRXD / FAULT
(See Note A)
5
3
FAULT LOGIC
MUX (See Note A)
VCC
VCC
VCC
OVER
TEMPERATURE
7
2 Applications
•
•
•
•
•
•
1-Mbps Operation in Highly Loaded CAN
Networks Down to 10-kbps Networks Using TXD
DTO
Industrial Automation, Control, Sensors, and Drive
Systems
Building, Security, and Climate Control
Automation
Telecom Base Station Status and Control
SN65HVD257: Functional Safety With Redundant
and Multitopology CAN networks
CAN Bus Standards Such as CANopen,
DeviceNet, NMEA2000, ARNIC825, ISO11783,
and CANaerospace
TXD
S
1
DOMINANT
TIME OUT
8
6
CANH
CANL
MODE SELECT
UNDER
VOLTAGE
VCC or V RXD (See Note B)
RXD
4
LOGIC
OUTPUT
DOMINANT
TIME OUT
(See Note B)
2
GND
A.
Pin 5 function is device dependent; NC on
the SN65HVD255 device, VRXD for RXD
output level-shifting device on the
SN65HVD256 device, and FAULT Output
on the SN65HVD257 device.
B.
RXD logic output is driven to 5-V VCC on
5-V only supply devices (SN65HVD255,
SN65HVD257) and driven to VRXD on the
output level-shifting device (SN65HVD256).
C.
RXD (Receiver) Dominant State Time Out
is a device-dependent option available only
on the SN65HVD257 device.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
SN65HVD255, SN65HVD256, SN65HVD257
SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Options.......................................................
Pin Configuration and Functions .........................
Specifications.........................................................
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
8
9
1
1
1
2
4
4
5
Absolute Maximum Ratings ...................................... 5
ESD Ratings.............................................................. 5
Recommended Operating Conditions....................... 6
Thermal Information .................................................. 6
Electrical Characteristics........................................... 7
Power Dissipation ..................................................... 9
Switching Characteristics .......................................... 9
Typical Characteristics ............................................ 10
Parameter Measurement Information ................ 11
Detailed Description ............................................ 14
9.1
9.2
9.3
9.4
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
14
14
14
19
10 Application and Implementation........................ 22
10.1 Application Information.......................................... 22
10.2 Typical Applications .............................................. 23
11 Power Supply Recommendations ..................... 27
12 Layout................................................................... 27
12.1 Layout Guidelines ................................................. 27
12.2 Layout Example .................................................... 28
13 Device and Documentation Support ................. 28
13.1
13.2
13.3
13.4
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
28
28
28
28
14 Mechanical, Packaging, and Orderable
Information ........................................................... 28
4 Revision History
Changes from Revision C (September 2013) to Revision D
•
Page
Added Pin Configuration and Functions section, ESD Ratings table, Switching Characteristics table, Typical
Characteristics section, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section ................................................................................................. 1
Changes from Revision B (June 2012) to Revision C
Page
•
Added Table 1, Receiver Differential Input Voltage Threshold Test .................................................................................... 12
•
Added Figure 13, Example Timing Diagram for TXD DTO and FAULT Pin ........................................................................ 17
•
Added Bus Loading, Length, and Number of Nodes subsection ......................................................................................... 22
Changes from Revision A (June 2012) to Revision B
•
Page
Added SN65HVD257 status to production in Ordering Information table .............................................................................. 4
Changes from Original (December 2011) to Revision A
Page
•
Updated the Features list ....................................................................................................................................................... 1
•
Updated the Applications list .................................................................................................................................................. 1
•
Added text to the Description section..................................................................................................................................... 1
•
Changed Block Diagram - Functional Block Diagram to include HVD257 and Note changes............................................... 1
•
Changed the DEVICE OPTIONS table................................................................................................................................... 4
•
Added SN65HVD257 to the D PACKAGE OPTIONS images................................................................................................ 4
•
Added SN65HVD257 FAULT pin to the PIN FUNCTIONS table ........................................................................................... 4
•
Added SN65HVD257 to the Ordering Information table......................................................................................................... 4
•
Added SN65HVD257 FAULT pin information to the Abs Max table ...................................................................................... 5
•
Added FAULT pin information to the ROC table .................................................................................................................... 6
2
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Copyright © 2011–2015, Texas Instruments Incorporated
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SN65HVD255, SN65HVD256, SN65HVD257
www.ti.com
SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
•
changed RID - Differential input resistance value from 3 kΩ to 30 kΩ.................................................................................... 8
•
Added tRXD_DTO - SN65HVD257 information ......................................................................................................................... 10
•
Added Figure 4, RXD Dominant Timeout Test Circuit and Measurement ........................................................................... 11
•
Added Figure 5, FAULT Test and Measurement ................................................................................................................. 11
•
Added RXD Dominant Timeout (SN65HVD257) section...................................................................................................... 15
•
Added FAULT pin information .............................................................................................................................................. 16
•
Added footnote for SN65HVD257 function to Table 5 ......................................................................................................... 19
•
Added 5-V VCC with FAULT Open-Drain Output Device (SN65HVD257) section................................................................ 21
•
Added Example: Functional Safety Using the SN65HVD257 in a Redundant Physical Layer CAN Network Topology
section .................................................................................................................................................................................. 24
Copyright © 2011–2015, Texas Instruments Incorporated
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3
SN65HVD255, SN65HVD256, SN65HVD257
SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
www.ti.com
5 Device Options
PART NUMBER
I/O
SUPPLY
for RXD
TXD
DTO
RXD
DTO
FAULT
Output
SN65HVD255
No
Yes
No
No
'251 and '1050 functional upgrade with Turbo CAN fast loop times and
TXD DTO protection allowing data rates down to 10 kbps
SN65HVD256
Yes
Yes
No
No
'251 and '1050 functional upgrade with Turbo CAN fast loop times and
TXD DTO protection allowing data rates down to 10 kbps. RXD output
level shifting through RXD supply input.
SN65HVD257
No
Yes
Yes
Yes
'251 and '1050 functional upgrade with Turbo CAN fast loop times, TXD
and RXD DTO protection allowing data rates down to 10 kbps and fault
output pin
COMMENT
6 Pin Configuration and Functions
D Package
8-Pin SOIC
(Top View)
SN65HVD255
SN65HVD257
SN65HVD256
TXD
1
8
S
TXD
1
8
S
TXD
1
8
S
GND
2
7
CANH
GND
2
7
CANH
GND
2
7
CANH
VCC
3
6
CANL
VCC
3
6
CANL
VCC
3
6
CANL
RXD
4
5
NC
RXD
4
5
VRXD
RXD
4
5
FAULT
5-V Supply and Fault
Output
5-V Supply with RXD
Level-Shifting
5-V Supply
Pin Functions
PIN
NAME
NO.
TYPE
TXD
1
GND
2
GND
VCC
3
Supply
RXD
4
O
5
Supply
NC
VRXD
I
NC
FAULT
DESCRIPTION
CAN transmit data input (LOW for dominant and HIGH for recessive bus states)
Ground connection
Transceiver 5-V supply voltage
CAN receive data output (LOW for dominant and HIGH for recessive bus states)
SN65HVD255: No Connect
SN65HVD256: RXD output supply voltage
O
SN65HVD257: Open drain FAULT output pin
CANL
6
I/O
Low level CAN bus line
CANH
7
I/O
High level CAN bus line
S
8
I
4
Mode select: S (silent mode) select pin (active high)
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SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
7 Specifications
7.1 Absolute Maximum Ratings (1) (2)
VCC
Supply voltage
VRXD
RXD Output supply voltage
VBUS
CAN Bus I/O voltage (CANH, CANL)
VLogic_Input
Logic input pin voltage (TXD, S)
SN65HVD256
MIN
MAX
UNIT
–0.3
6.1
V
–0.3
6 and VRXD ≤ VCC + 0.3
V
–27
40
V
–0.3
6
V
–0.3
6
V
–0.3
6 and VI ≤ VRXD + 0.3
V
12
mA
VLogic_Output
Logic output pin voltage (RXD)
SN65HVD255,
SN65HVD257
VLogic_Output
Logic output pin voltage (RXD)
SN65HVD256
IO(RXD)
RXD (Receiver) output current
IO(FAULT)
FAULT output current
20
mA
TJ
Operating virtual junction temperature (see Power Dissipation)
–40
150
°C
TA
Ambient temperature (see Power Dissipation)
–40
125
°C
(1)
(2)
SN65HVD257
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values, except differential I/O bus voltages, are with respect to ground terminal.
7.2 ESD Ratings
VALUE UNIT
Human body model (HBM), per
ANSI/ESDA/JEDEC JS-001 (1)
V(ESD)
Electrostatic
discharge
All pins
±2500
CAN bus pins (CANH, CANL) (2)
±12000
Charged-device model (CDM), per JEDEC
specification JESD22-C101 (3)
All pins
±750
Machine model
All pins
±250
IEC 61400-4-2 according to GIFT-ICT CAN EMC
CAN bus pins (CANH, CANL) to GND
test spec (4)
Pulse 1
ISO7637 Transients according to GIFT - ICT
CAN EMC test spec (5)
(1)
(2)
(3)
(4)
(5)
±8000
V
–100
CAN bus pins (CANH, Pulse 2
CANL)
Pulse 3a
+75
–150
Pulse 3b
+100
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
Test method based upon JEDEC Standard 22 Test Method A114, CAN bus pins stressed with respect to GND.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
IEC 61000-4-2 is a system level ESD test. Results given here are specific to the GIFT-ICT CAN EMC Test specification conditions.
Different system level configurations may lead to different results.
ISO7637 is a system level transient test. Results given here are specific to the GIFT-ICT CAN EMC Test specification conditions.
Different system level configurations may lead to different results.
Copyright © 2011–2015, Texas Instruments Incorporated
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SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
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7.3 Recommended Operating Conditions
MIN
MAX
VCC
Supply voltage
4.5
5.5
VRXD
RXD supply (SN65HVD256 only)
2.8
5.5
VI or VIC
CAN bus terminal voltage (separately or common mode)
–2
7
VID
CAN bus differential voltage
-6
6
VIH
Logic HIGH level input (TXD, S)
2
5.5
VIL
Logic LOW level input (TXD, S)
0
0.8
IOH(DRVR)
CAN BUS Driver High level output current
IOL(DRVR)
CAN BUS Driver Low level output current
IOH(RXD)
RXD pin HIGH level output current
IOL(RXD)
RXD pin LOW level output current
IO(FAULT)
FAULT pin LOW level output current
TA
Operational free-air temperature (see Power Dissipation)
UNIT
V
–70
70
–2
mA
2
SN65HVD257
2
–40
125
°C
7.4 Thermal Information
SN65HVD25x
THERMAL METRIC (1)
D (SOIC)
UNIT
8 PINS
RθJA
Junction-to-ambient thermal resistance, High-K thermal resistance (2)
107.5
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
56.7
°C/W
RθJB
Junction-to-board thermal resistance
48.9
°C/W
ψJT
Junction-to-top characterization parameter
12.1
°C/W
ψJB
Junction-to-board characterization parameter
48.2
°C/W
(1)
(2)
6
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, High-K board, as
specified in JESD51-7, in an environment described in JESD51-2a.
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SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
7.5 Electrical Characteristics
Over recommended operating conditions, TA = –40°C to 125°C (unless otherwise noted). SN65HVD256 device VRXD = VCC.
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
60
85
130
180
UNIT
SUPPLY CHARACTERISTICS
5-V Supply
current
ICC
Normal Mode
(Driving
Dominant)
See Figure 6, TXD = 0 V, RL = 50 Ω,
CL = open, RCM = open, S = 0 V
Normal Mode
(Driving
Dominant – bus
fault)
See Figure 6, TXD = 0 V, S = 0 V,
CANH = –12 V, RL = open, CL = open,
RCM = open
Normal Mode
(Driving
Dominant)
See Figure 6, TXD = 0 V,
RL = open (no load),
CL = open, RCM = open, S = 0 V
10
20
Normal Mode
(Recessive)
See Figure 6, TXD = VCC, RL = 50 Ω,
CL = open, RCM = open,
S=0V
10
20
Silent Mode
See Figure 6, TXD = VCC, RL = 50 Ω,
CL = open, RCM = open, S = VCC
2.5
5
All modes
RXD Floating, TXD = 0 V
IRXD
RXD Supply
current
(SN65HVD256
only)
UVVCC
Undervoltage detection on VCC for
protected mode
VHYS(UVVCC)
Hysteresis voltage on UVVCC
UVRXD
Undervoltage detection on VRXD for
protected mode (SN65HVD256 only)
VHYS(UVRXD)
Hysteresis voltage on UVRXD
(SN65HVD256 only)
mA
3.5
500
µA
4.45
V
200
1.3
mV
2.75
80
V
mV
S PIN (MODE SELECT INPUT)
VIH
HIGH-level input voltage
VIL
LOW-level input voltage
2
IIH
HIGH-level input leakage current
S = VCC = 5.5 V
IIL
Low-level input leakage current
S = 0 V, VCC = 5.5 V
ILKG(OFF)
Unpowered leakage current
S = 5.5 V, VCC = 0 V, VRXD = 0 V
V
7
0.8
V
100
µA
–1
0
1
µA
7
35
100
µA
TXD PIN (CAN TRANSMIT DATA INPUT)
VIH
HIGH level input voltage
VIL
LOW level input voltage
2
IIH
HIGH level input leakage current
TXD = VCC = 5.5 V
–2.5
IIL
Low level input leakage current
TXD = 0 V, VCC = 5.5 V
ILKG(OFF)
Unpowered leakage current
TXD = 5.5 V, VCC = 0 V, VRXD = 0 V
CI
Input Capacitance
V
0.8
V
0
1
µA
–100
–25
–7
µA
–1
0
1
µA
3.5
pF
RXD PIN (CAN RECEIVE DATA OUTPUT)
VOH
HIGH level output voltage
See Figure 7, IO = –2 mA. For devices with
VRXD supply VOH = 0.8 × VRXD
VOL
LOW level output voltage
See Figure 7, IO = 2 mA
ILKG(OFF)
Unpowered leakage current
RXD = 5.5 V, VCC = 0 V, VRXD = 0 V
(1)
0.8 × VCC
–1
V
0
0.4
V
1
µA
All typical values are at 25°C and supply voltages of VCC = 5 V and VRXD = 5 V, RL = 60 Ω.
Copyright © 2011–2015, Texas Instruments Incorporated
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Electrical Characteristics (continued)
Over recommended operating conditions, TA = –40°C to 125°C (unless otherwise noted). SN65HVD256 device VRXD = VCC.
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
DRIVER ELECTRICAL CHARACTERISTICS
CANH
VO(D)
Bus output
voltage
(dominant)
VO(R)
Bus output voltage (recessive)
CANL
Differential output voltage
(dominant)
VOD(D)
Differential output voltage
(recessive)
VOD(R)
VSYM
Output symmetry (dominant or
recessive)
(VCC – VO(CANH) – VO(CANL))
IOS(SS)_DOM
Short circuit steady-state output
current, Dominant
See Figure 15 and Figure 6, TXD = 0 V,
S = 0 V, RL = 60 Ω, CL = open,
RCM = open
See Figure 15 and Figure 6, TXD = VCC,
VRXD = VCC, S = VCC or 0 V (2), RL = open
(no load), RCM = open
See Figure 15 and Figure 6, TXD = 0 V,
S = 0 V, 45 Ω ≤ RL ≤ 65 Ω, CL = open,
RCM = 330 Ω, –2 V ≤ VCM ≤ 7 V, 4.75 V≤
VCC ≤ 5.25 V
See Figure 15 and Figure 6, TXD = 0 V, S
= 0 V, 45 Ω ≤ RL ≤ 65 Ω, CL = open,
RCM = 330 Ω, –2 V ≤ VCM ≤ 7 V,
4.5 V ≤ VCC ≤ 5.5 V
2.75
4.5
0.5
2.25
2 0.5 × VCC
1.5
3
V
3.2
See Figure 15 and Figure 6, TXD = VCC,
S = 0 V, RL = 60 Ω, CL = open,
RCM = open
–0.12
0.012
See Figure 15 and Figure 6, TXD = VCC,
S = 0 V, RL = open (no load), CL = open,
RCM = open, –40°C ≤ TA ≤ 85°C
–0.100
0.050
See Figure 15 and Figure 6, S at 0 V,
RL = 60 Ω, CL = open, RCM = open
–0.4
0.4
See Figure 15 and Figure 11, VCANH = 0 V,
CANL = open, TXD = 0 V
–160
V
IOS(SS)_REC
CO
Output capacitance
See Input capacitance to ground (CI) in the
following Receiver Electrical Characteristics
section of this table
V
mA
See Figure 15 and Figure 11,
VCANL = 32 V, CANH = open, TXD = 0 V
See Figure 15 and Figure 11,
–20 V ≤ VBUS ≤ 32 V, Where VBUS = CANH
= CANL,
TXD = VCC, Normal and Silent Modes
V
3
1.25
Short circuit steady-state output
current, Recessive
V
160
–8
8
mA
900
mV
RECEIVER ELECTRICAL CHARACTERISTICS
Positive-going input threshold
voltage, normal mode
VIT+
See Figure 7, Table 5 and Table 1
VIT–
Negative-going input threshold
voltage, normal mode
VHYS
Hysteresis voltage (VIT+ - VIT–)
IIOFF(LKG)
Power-off (unpowered) bus input
leakage current
VCANH = VCANL = 5 V,
VCC = 0 V, VRXD = 0 V
CI
Input capacitance to ground (CANH
or CANL)
TXD = VCC, VRXD = VCC,
VI = 0.4 sin (4E6 π t) + 2.5 V
25
pF
CID
Differential input capacitance
TXD = VCC, VRXD = VCC,
VI = 0.4 sin (4E6 π t)
10
pF
RID
Differential input resistance
RIN
Input resistance (CANH or CANL)
RIN(M)
Input resistance matching:
[1 – RIN(CANH) / RIN(CANL)] × 100%
(2)
8
500
mV
125
mV
5.5
TXD = VCC = VRXD = 5 V, S = 0 V
V(CANH) = V(CANL), –40°C ≤ TA ≤ 85°C
µA
30
80
kΩ
15
40
kΩ
–3%
3%
For the bus output voltage (recessive) will be the same if the device is in normal mode with S pin LOW or if the device is in silent mode
with the S pin HIGH.
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SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
Electrical Characteristics (continued)
Over recommended operating conditions, TA = –40°C to 125°C (unless otherwise noted). SN65HVD256 device VRXD = VCC.
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
FAULT PIN (FAULT OUTPUT), SN65HVD257 ONLY
ICH
Output current high level
FAULT = VCC, see Figure 5
ICL
Output current low level
FAULT = 0.4 V, see Figure 5
–10
10
5
12
µA
mA
7.6 Power Dissipation
THERMAL METRIC
TEST CONDITIONS
TYP
VCC = 5 V, VRXD = 5 V, TJ = 27°C, RL = 60 Ω, S at 0 V, Input to TXD at
250 kHz, 25% duty cycle square wave, CL_RXD = 15 pF. Typical CAN
operating conditions at 500 kbps with 25% transmission (dominant) rate.
PD
Average power dissipation
UNIT
115
mW
VCC = 5.5 V, VRXD = 5.5 V, TJ = 150°C, RL = 50 Ω, S at 0 V, Input to TXD
at 500 kHz, 50% duty cycle square wave, CL_RXD = 15 pF. Typical high
load CAN operating conditions at 1 Mbps with 50% transmission
(dominant) rate and loaded network.
268
Thermal shutdown temperature
Thermal shutdown hysteresis
170
°C
5
°C
7.7 Switching Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
DEVICE SWITCHING CHARACTERISTICS
tPROP(LOOP1)
Total loop delay, driver input (TXD) to
receiver output (RXD), recessive to
dominant
tPROP(LOOP2)
Total loop delay, driver input (TXD) to
receiver output (RXD), dominant to
recessive
IMODE
Mode change time, from Normal to Silent
or from Silent to Normal
150
See Figure 9, S = 0 V, RL = 60 Ω,
CL = 100 pF, CL_RXD = 15 pF
ns
150
See Figure 8
20
µS
DRIVER SWITCHING CHARACTERISTICS
tpHR
Propagation delay time, HIGH TXD to
Driver Recessive
tpLD
Propagation delay time, LOW TXD to
Driver Dominant
tsk(p)
Pulse skew (|tpHR – tpLD|)
tR
Differential output signal rise time
10
30
tF
Differential output signal fall time
17
30
tR(10k)
Differential output signal rise time,
RL = 10 kΩ
tF(10k)
Differential output signal fall time,
RL = 10 kΩ
tTXD_DTO
Dominant timeout (1)
(1)
See Figure 6, S = 0 V, RL = 60 Ω,
CL = 100 pF, RCM = open
50
70
40
70
ns
10
35
See Figure 6, S = 0 V, RL = 10 kΩ,
CL = 10 pF, RCM = open
ns
100
See Figure 10, RL = 60 Ω, CL = open
1175
3700
µs
The TXD dominant timeout (tTXD_DTO) disables the driver of the transceiver when the TXD has been dominant longer than tTXD_DTO,
which releases the bus lines to recessive, thus preventing a local failure from locking the bus dominant. The driver may only transmit
dominant again after TXD has been returned HIGH (recessive). While this protects the bus from local faults locking the bus dominant, it
limits the minimum data rate possible. The CAN protocol allows a maximum of eleven successive dominant bits (on TXD) for the worst
case, where five successive dominant bits are followed immediately by an error frame. This, along with the tTXD_DTO minimum, limits the
minimum bit rate. The minimum bit rate may be calculated by: Minimum Bit Rate = 11 / tTXD_DTO = 11 bits / 1175 µs = 9.4 kbps.
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Switching Characteristics (continued)
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
70
90
ns
70
90
ns
RECEIVER SWITCHING CHARACTERISTICS
tpRH
Propagation delay time, recessive input to
high output
tpDL
Propagation delay time, dominant input to
low output
tR
Output signal rise time
4
20
ns
tF
Output signal fall time
4
20
ns
tRXD_DTO (2)
Receiver dominant time out (SN65HVD257
only) See Figure 4, CL_RXD = 15 pF
4200
µs
(2)
See Figure 7, CL_RXD = 15 pF
1380
The RXD timeout (tRXD_DTO) disables the RXD output in the case that the bus has been dominant longer than tRXD_DTO, which releases
RXD pin to the recessive state (high), thus preventing a dominant bus failure from permanently keeping the RXD pin low. The RXD pin
will automatically resume normal operation once the bus has been returned to a recessive state. While this protects the protocol
controller from a permanent dominant state, it limits the minimum data rate possible. The CAN protocol allows a maximum of eleven
successive dominant bits (on RXD) for the worst case, where five successive dominant bits are followed immediately by an error frame.
This, along with the tRXD_DTO minimum, limits the minimum bit rate. The minimum bit rate may be calculated by: Minimum Bit Rate = 11 /
tRXD_DTO = 11 bits / 1380 µs = 8 kbps.
7.8 Typical Characteristics
4.8
4.4
4.6
4.2
4.4
4
VOD (V)
VOD (V)
4.2
4
3.8
3.8
3.6
3.6
3.4
3.4
3.2
3.2
3
4.3
4.5
4.7
4.9
5.1
VCC (V)
5.3
5.5
3
-50
5.7
0
D001
Figure 1. Differential Output Voltage vs Supply Voltage
50
100
Temperature (qC)
150
200
D002
Figure 2. Differential Output Voltage vs Ambient
Temperature
140
120
Time (ns)
100
80
60
40
20
0
40
45
50
55
60
RL - Bus Load (:)
65
70
C024
Figure 3. Typical Transceiver Loop Delay vs Bus Loading
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8 Parameter Measurement Information
VID(D)
CANH
VID
RXD
0.9V
0.5V
0V
VID
CL_RXD
CANL
VO
VOH
RXD
50%
0V
t RXD_DTO
Figure 4. RXD Dominant Timeout Test Circuit and Measurement
IFAULT
TXD
DTO
FAULT
RXD
DTO
+
-
Thermal
Shutdown
UV
Lockout
GND
Figure 5. FAULT Test and Measurement
RCM
CANH
TXD
VCC
TXD
RL
CL
VOD
VO(CANL)
50%
0V
VCM
VO(CANH)
CANL
50%
tpHR
tpLD
90%
RCM
VOD
0.9 V
0.5 V
10%
tR
tF
Figure 6. Driver Test Circuit and Measurement
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Parameter Measurement Information (continued)
CANH
1 .5 V
RXD
0 .9 V
IO
V ID
0 .5 V
0V
VID
CL_RXD
CANL
t pDL
t pRH
VO
V OH
90 %
V O(RXD)
50 %
10 %
V OL
tF
tR
Figure 7. Receiver Test Circuit and Measurement
CANH
0V
VCC
TXD
RL
CL
S
50%
CANL
VI
S
0V
tMODE
RXD
VO
VOH
CL_RXD
RXD
50%
VOL
Figure 8. tMODE Test Circuit and Measurement
Table 1. Receiver Differential Input Voltage Threshold Test
INPUT
12
OUTPUT
VCANH
VCANL
|VID|
–1.1 V
–2.0 V
900 mV
L
7.0 V
6.1 V
900 mV
L
–1.5 V
–2.0 V
500 mV
H
7.0 V
6.5 V
500 mV
H
Open
Open
X
H
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RXD
VOL
VOH
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CANH
VCC
TXD
RL
VI
CL
50%
TXD
0V
CANL
S
0V
tPROP(LOOP1)
RXD
VO
tPROP(LOOP2)
VOH
CL_RXD
50%
RXD
VOL
Figure 9. TPROP(LOOP) Test Circuit and Measurement
CANH
TXD
VIH
TXD
RL
CL
0V
VOD
VOD(D)
CANL
0.9 V
VOD
0.5 V
0V
tTXD_DTO
Figure 10. TXD Dominant Timeout Test Circuit and Measurement
CANH
IOS
200 ms
TXD
IOS
CANL
VBUS
VBUS
VBUS
0V
or
0V
VBUS
VBUS
Figure 11. Driver Short Circuit Current Test and Measurement
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9 Detailed Description
9.1 Overview
The SN65HVD25x family of bus transceiver devices are compatible with the ISO 11898-2 High Speed CAN
(Controller Area Network) physical layer standard. The SN65HVD25x devices are designed to interface between
the differential bus lines and the CAN protocol controller at data rates up to 1 Mbps (megabits per second).
9.2 Functional Block Diagram
NC / VRXD / FAULT
(See Note A)
5
3
FAULT LOGIC
MUX (See Note A)
VCC
VCC
VCC
OVER
TEMPERATURE
7
TXD
S
1
DOMINANT
TIME OUT
8
6
CANH
CANL
MODE SELECT
UNDER
VOLTAGE
VCC or V RXD (See Note B)
RXD
4
LOGIC
OUTPUT
DOMINANT
TIME OUT
(See Note B)
2
GND
A.
Pin 5 function is device dependent; NC on SN65HVD255, VRXD for RXD output level-shifting device on the
SN65HVD256 device, and FAULT Output on the SN65HVD257 device.
B.
RXD logic output is driven to 5-V VCC on 5-V only supply devices (SN65HVD255, SN65HVD257) and driven to VRXD
on output level-shifting device (SN65HVD256).
C.
RXD (Receiver) Dominant State Time Out is a device dependent option available only on the SN65HVD257 device.
9.3 Feature Description
9.3.1 TXD Dominant Timeout (DTO)
During normal mode (the only mode where the CAN driver is active), the TXD DTO circuit prevents the
transceiver from blocking network communication in the event of a hardware or software failure where TXD is
held dominant longer than the timeout period tTXD_DTO. The DTO circuit timer starts on a falling edge on TXD.
The DTO circuit disables the CAN bus driver if no rising edge is seen before the timeout period expires, which
frees the bus for communication between other nodes on the network. The CAN driver is reactivated when a
recessive signal is seen on TXD pin, thus clearing the TXD DTO condition. The receiver and RXD pin still reflect
the CAN bus, and the bus pins are biased to recessive level during a TXD dominant timeout.
NOTE
The minimum dominant TXD time allowed by the TXD DTO circuit limits the minimum
possible transmitted data rate of the device. The CAN protocol allows a maximum of
eleven successive dominant bits (on TXD) for the worst case, where five successive
dominant bits are followed immediately by an error frame. This, along with the tTXD_DTO
minimum, limits the minimum data rate. Calculate the minimum transmitted data rate by:
Minimum Data Rate = 11 / tTXD_DTO.
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Feature Description (continued)
9.3.2 RXD Dominant Timeout (SN65HVD257)
The SN65HVD257 device has a RXD dominant timeout (RXD DTO) circuit that prevents a bus stuck dominant
fault from permanently driving the RXD output dominant (low) when the bus is held dominant longer than the
timeout period tRXD_DTO. The RXD DTO timer starts on a falling edge on RXD (bus going dominant). If no rising
edge (bus returning recessive) is seen before the timeout constant of the circuit expires (tRXD_DTO), the RXD pin
returns high (recessive). The RXD output is reactivated to mirror the bus receiver output when a recessive signal
is seen on the bus, clearing the RXD dominant timeout. The CAN bus pins are biased to the recessive level
during a RXD DTO.
NOTE
The minimum dominant RXD time allowed by the RXD DTO limits the minimum possible
received data rate of the device. The CAN protocol allows a maximum of eleven
successive dominant bits for the worst case transmission, where five successive dominant
bits are followed immediately by an error frame. This, along with the tRXD_DTO minimum,
limits the minimum data rate. The minimum received data rate may be calculated by:
Minimum Data Rate = 11 / tRXD_DTO.
9.3.3 Thermal Shutdown
If the junction temperature of the device exceeds the thermal shut down threshold, the device turns off the CAN
driver circuits thus blocking the TXD to bus transmission path. The shutdown condition is cleared when the
junction temperature drops below the thermal shutdown temperature of the device.
NOTE
During thermal shutdown the CAN bus drivers turn off; thus, no transmission is possible
from TXD to the bus. The CAN bus pins are biased to recessive level during a thermal
shutdown, and the receiver to RXD path remains operational.
9.3.4 Undervoltage Lockout
The supply pins have undervoltage detection that places the device in protected mode, which protects the bus
during an undervoltage event on either the VCC or VRXD supply pins.
Table 2. Undervoltage Lockout 5-V Only Devices (SN65HVD255 and SN65HVD257)
VCC
DEVICE STATE
BUS OUTPUT
RXD
GOOD
Normal
Per Device State and TXD
Mirrors Bus
BAD
Protected
High Impedance
High Impedance (3-state)
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Table 3. Undervoltage Lockout 5 V and VRXD Device (SN65HVD256)
VCC
VRXD
DEVICE STATE
BUS OUTPUT
RXD
GOOD
GOOD
Normal
Per Device State and TXD
Mirrors Bus
BAD
GOOD
Protected
High Impedance
High (Recessive)
GOOD
BAD
Protected
Recessive
High Impedance (3-state)
BAD
BAD
Protected
High Impedance
High Impedance (3-state)
NOTE
After an undervoltage condition is cleared and the supplies have returned to valid levels,
the device typically resumes normal operation in 300 µs.
9.3.5 FAULT Pin (SN65HVD257)
If one or more of the faults (TXD dominant timeout, RXD dominant timeout, thermal shutdown or undervoltage
lockout) occurs, the FAULT pin (open-drain) turns off, resulting in a high level when externally pulled up to VCC or
I/O supply.
VCC or VIO
µP
FAULT
Input
FAULT
TXD
DTO
RXD
DTO
Thermal
Shutdown
GND
UV
Lockout
Figure 12. FAULT Pin Function Diagram and Application
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TXD fault stuck dominant, example PCB
failure or bad software
TXD
(driver)
tTXD_DTO
Fault is repaired & transmission
capability restored
Driver disabled freeing bus for other nodes
%XVZRXOGEH³VWXFNGRPLQDQW´EORFNLQJFRPPXQLFDWLRQIRUWKH
whole network but TXD DTO prevents this and frees the bus for
communication after the time tTXD_DTO.
Normal CAN
communication
CAN
Bus
Signal
tTXD_DTO
Communication from
other bus node(s)
Communication from
repaired node
FAULT is signaled to link layer / protocol.
Fault indication is removed.
FAULT
(HVD257)
RXD
(receiver)
Communication from
other bus node(s)
Communication from
local node
Communication from
repaired local node
Figure 13. Example Timing Diagram for TXD DTO and FAULT Pin
Bus Fault stuck dominant , example CANH
short to supply =5V and CAN L short to GND .
Fault is repaired and normal
communication returns
SN65HVD255
SN65HVD256
CAN
Bus
Signal
SN65HVD257
CAN PHY With RXD
DTO AND FAULT
CAN PHY
CAN BUS
Normal CAN
communication
RXD
(receiver)
RXD will also be “stuck dominant” blocking
alternative communication paths
RXD
(reciever)
t RXD_DTO
RXD output is returned recessive (high)
and FAULT is signaled to μP and link
layer / protocol.
RXD mirrors
bus
FAULT cleared signal
is given
FAULT
Figure 14. Example Timing Diagram for Devices With and Without RXD DTO and FAULT Pin
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9.3.6 Unpowered Device
The SN65HVD25x device is designed to be an ideal passive or no load to the CAN bus if it is unpowered. The
bus pins (CANH, CANL) have extremely low leakage currents when the device is unpowered, so they will not
load down the bus. This is critical if some nodes of the network will be unpowered while the rest of the of network
remains in operation. The logic pins also have extremely low leakage currents when the device is unpowered to
avoid loading down other circuits that may remain powered.
9.3.7 Floating Pins
The device has internal pullups and pulldowns on critical pins to place the device into known states if the pins
float. The TXD pin is pulled up to VCC to force a recessive input level if the pin floats. The S pin is pulled down to
GND to force the device into normal mode if the pin floats.
9.3.8 CAN Bus Short-Circuit Current Limiting
The SN65HVD25x device has several protection features that limit the short circuit current when a CAN bus line
is shorted. These features include driver current limiting (dominant and recessive). The device has TXD
dominant state time out to prevent permanent higher short circuit current of the dominant state during a system
fault. During CAN communication, the bus switches between dominant and recessive states with the data and
control fields bits; thus the short circuit current may be viewed either as the instantaneous current during each
bus state or as a DC average current. For system current (power supply) and power considerations in the
termination resistors and common-mode choke ratings, use the average short circuit current. Determine the ratio
of dominant and recessive bits by the data in the CAN frame plus the following factors of the protocol and PHY
that force either recessive or dominant at the following times:
•
•
•
•
Control fields with set bits
Bit stuffing
Interframe space
TXD dominant time out (fault case limiting)
These factors ensure a minimum recessive amount of time on the bus even if the data field contains a high
percentage of dominant bits.
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The short circuit current of the bus depends on the ratio of recessive to dominant bits and their respective short
circuit currents. The average short circuit current may be calculated with Equation 1.
IOS(AVG) = %Transmit × [(%REC_Bits × IOS(SS)_REC) + (%DOM_Bits × IOS(SS)_DOM)] + [%Receive × IOS(SS)_REC]
(1)
where:
IOS(AVG) is the average short circuit current
%Transmit is the percentage the node is transmitting CAN messages
%Receive is the percentage the node is receiving CAN messages
%REC_Bits is the percentage of recessive bits in the transmitted CAN messages
%DOM_Bits is the percentage of dominant bits in the transmitted CAN messages
IOS(SS)_REC is the recessive steady state short circuit current
IOS(SS)_DOM is the dominant steady state short circuit current
NOTE
Consider the short circuit current and possible fault cases of the network when sizing the
power ratings of the termination resistance and other network components.
9.4 Device Functional Modes
Table 4. Driver Function Table
INPUTS
DEVICE
S (1) (2)
L or Open
All Devices
H
(1)
(2)
(3)
OUTPUTS
TXD (1) (3)
CANH (1)
CANL (1)
DRIVEN BUS
STATE
L
H
L
Dominant
H or Open
Z
Z
Recessive
X
Z
Z
Recessive
H = high level, L = low level, X= irrelevant, Z = common mode (recessive) bias to VCC / 2. See
Figure 15 and Figure 16 for bus state and common mode bias information.
Devices have an internal pulldown to GND on S pin. If S pin is open the pin will be pulled low and the
device will be in normal mode.
Devices have an internal pullup to VCC on TXD pin. If the TXD pin is open the pin will be pulled high
and the transmitter will remain in recessive (nondriven) state.
Table 5. Receiver Function Table
DEVICE MODE
Normal or Silent
(1)
(2)
CAN DIFFERENTIAL INPUTS
VID = VCANH – VCANL
BUS STATE
RXD PIN (1)
VID ≥ 0.9 V
Dominant
L (2)
0.5 V < VID < 0.9 V
?
?
VID ≤ 0.5 V
Recessive
H
Open (VID ≈ 0 V)
Open
H
H = high level, L = low level, ? = indeterminate.
RXD output remains dominant (low) as long as the bus is dominant. On the SN65HVD257 device with
RXD dominant timeout, when the bus has been dominant longer than the dominant timeout, tRXD_DTO,
the RXD pin will return recessive (high). See RXD Dominant Timeout (SN65HVD257) for a description
of behavior during receiving a bus stuck dominant condition.
9.4.1 Operating Modes
The device has two main operating modes: normal mode and silent mode. Operating mode selection is made via
the S input pin.
Table 6. Operating Modes
(1)
S Pin
MODE
DRIVER
RECEIVER
RXD PIN
LOW
Normal Mode
Enabled (ON)
Enabled (ON)
Mirrors Bus State (1)
HIGH
Silent Mode
Disabled (OFF)
Enabled (ON)
Mirrors Bus State
Mirrors bus state: low if CAN bus is dominant, high if CAN bus is recessive.
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9.4.2 Can Bus States
The CAN bus has two states during powered operation of the device: dominant and recessive. A dominant bus
state is when the bus is driven differentially, corresponding to a logic low on the TXD and RXD pin. A recessive
bus state is when the bus is biased to VCC / 2 via the high-resistance internal input resistors RIN of the receiver,
corresponding to a logic high on the TXD and RXD pins. See Figure 15 and Figure 16.
Typical Bus Voltage (V)
Normal & Silent Mode
4
CANH
3
Vdiff(D)
2
Vdiff(R)
CANL
1
Recessive
Logic H
Dominant
Logic L
Recessive
Logic H
Time, t
Figure 15. Bus States (Physical Bit Representation)
CANH
VCC/2
RXD
CANL
Figure 16. Simplified Recessive Common Mode Bias and Receiver
9.4.3 Normal Mode
Select the normal mode of device operation by setting S low. The CAN driver and receiver are fully operational
and CAN communication is bidirectional. The driver is translating a digital input on TXD to a differential output on
CANH and CANL. The receiver is translating the differential signal from CANH and CANL to a digital output on
RXD.
9.4.4 Silent Mode
Activate silent mode (receive only) by setting S high. The CAN driver is turned off while the receiver remains
active and RXD outputs the received bus state.
NOTE
Silent mode may be used to implement babbling idiot protection, to ensure that the driver
does not disrupt the network during a local fault. Silent mode may also be used in
redundant systems to select or de-select the redundant transceiver (driver) when needed.
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9.4.5 Digital Inputs and Outputs
9.4.5.1 5-V VCC Only Devices (SN65HVD255 and SN65HVD257)
The 5-V VCC device is supplied by a single 5-V rail. The digital inputs are 5-V and 3.3-V compatible. The
SN65HVD255 and SN65HVD257 devices have a 5-V (VCC) level RXD output. TXD is internally pulled up to VCC
and S is internally pulled down to GND.
NOTE
TXD is internally pulled up to VCC and the S pin is internally pulled down to GND.
However, the internal bias may only put the device into a known state if the pins float. The
internal bias may be inadequate for system-level biasing. TXD pullup strength and CAN bit
timing require special consideration when the SN65HVD25x devices are used with an
open-drain TXD output on the CAN controller. An adequate external pullup resistor must
be used to ensure that the CAN controller output of the μP maintains adequate bit timing
input to the SN65HVD25x devices.
9.4.5.2 5-V VCC With VRXD RXD Output Supply Devices (SN65HVD256)
This device is a 5-V VCC CAN transceiver with a separate supply for the RXD output, VRXD. The digital inputs are
5-V and 3.3-V compatible. The SN65HVD256 device has a VRXD level RXD output. TXD remains weakly pulled
up to VCC.
NOTE
On device versions with a VRXD supply that shifts the RXD output level, the input pins of
the device remain the same. TXD remains weakly pulled up to VCC internally. Thus, a
small IIH current flows if the TXD input is used below VCC levels.
9.4.5.3 5-V VCC with FAULT Open-Drain Output Device (SN65HVD257)
The SN65HVD257 device has a FAULT output pin (open-drain). FAULT must be pulled up to VCC or I/O supply
level through an external resistor.
NOTE
Because the FAULT output pin is open-drain, it actively pulls down when there is no fault
and becomes high-impedance when a fault condition is detected. An external pullup
resistor to the VCC or I/O supply of the system must be used to pull the pin high to indicate
a fault to the host microprocessor. The open-drain architecture makes the fault pin
compatible with 3.3-V and 5-V I/O-level systems. The pullup current, selected by the
pullup resistance value, must be as low as possible while achieving the desired voltage
level output in the system with margin against noise.
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10 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
10.1.1 Bus Loading, Length, and Number of Nodes
The ISO 11898 standard states that a CAN bus should have a maximum of 30 nodes, be less than 40 meters
from end to end, and should have no stubs greater than 0.3 meters. However, with careful design, users can
have longer cables, longer stub lengths, and many more nodes to a bus. A large number of nodes requires a
transceiver with high input impedance, such as the SN65HVD25x family devices.
Many CAN organizations and standards have scaled the use of CAN for applications outside the original
ISO11898 standard. They have made system level trade-offs for data rate, cable length, and parasitic loading of
the bus. Examples of some of these specifications are: ARINC825, CANopen, DeviceNet, and NMEA200.
A CAN network design is a series of trade-offs, but these devices operate over wide common-mode range. In
ISO11898-2, the driver differential output is specified with a 60-Ω load (the two 120-Ω termination resistors in
parallel) and the differential output must be greater than 1.5 V. The SN65HVD25x devices are specified to meet
the 1.5-V requirement with a 45-Ω load incorporating the worst case including parallel transceivers. The
differential input resistance of the SN65HVD25x devices is a minimum of 30 KΩ. If 167 SN65HVD25x family
transceivers are in parallel on a bus, this is equivalent to a 180-Ω differential load worst case. That transceiver
load of 180 Ω in parallel with the 60 Ω gives a total 45 Ω. Therefore, the SN65HVD25x family theoretically
supports over 167 transceivers on a single bus segment with margin to the 1.2-V minimum differential input at
each node. However, CAN network design margin must be given for signal loss across the system and cabling,
parasitic loadings, network imbalances, ground offsets, and signal integrity; thus a practical maximum number of
nodes is typically much lower. Bus length may also be extended beyond the original ISO11898 standard of 40 m
by careful system design and data-rate tradeoffs. For example, CAN open network design guidelines allow the
network to be up to 1 km with changes in the termination resistance, cabling, less than 64 nodes, and a
significantly lowered data rate.
This flexibility in CAN network design is one of the key strengths of the various extensions and additional
standards that have been built on the original ISO11898 CAN standard. In using this flexibility comes the
responsibility of good network design and balancing these tradeoffs.
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10.2 Typical Applications
10.2.1 Typical 5-V Microcontroller Application
VIN
VIN
VOUT
5-V Voltage
Regulator
(e.g.TPSxxxx)
VCC
VCC
3
Port x
S
7
CANH
8
SN65HVD255
5-V MCU
CAN Transceiver
RXD
TXD
RXD
TXD
4
1
5
NC
6
2
CANL
GND
Figure 17. Typical 5-V Application
10.2.1.1 Design Requirements
10.2.1.1.1 CAN Termination
The ISO11898 standard specifies the interconnect to be a twisted-pair cable (shielded or unshielded) with 120-Ω
characteristic impedance (ZO). Resistors equal to the characteristic impedance of the line must be used to
terminate both ends of the cable to prevent signal reflections. Unterminated drop lines (stubs) connecting nodes
to the bus must be kept as short as possible to minimize signal reflections. The termination may be on the cable
or in a node, but if nodes may be removed from the bus, the termination must be carefully placed so that it is not
removed from the bus.
Node 1
Node 2
Node 3
MCU or DSP
MCU or DSP
MCU or DSP
CAN
Controller
CAN
Controller
CAN
Controller
CAN
Transceiver
CAN
Transceiver
CAN
Transceiver
Node n
(with termination)
MCU or DSP
CAN
Controller
CAN
Transceiver
RTERM
RTERM
Figure 18. Typical CAN Bus
Termination may be a single 120-Ω resistor at the end of the bus either on the cable or in a terminating node. If
filtering and stabilization of the common mode voltage of the bus is desired, then split termination may be used
(see Figure 19). Split termination improves the electromagnetic emissions behavior of the network by eliminating
fluctuations in the bus common-mode voltages at the start and end of message transmissions.
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Typical Applications (continued)
Standard Termination
CANH
Split Termination
CANH
RTERM/2
CAN
CAN
Transceiver
RTERM
Transceiver
CSPLIT
RTERM/2
CANL
CANL
Figure 19. CAN Bus Termination Concepts
10.2.1.2 Detailed Design Procedure
10.2.1.2.1 Example: Functional Safety Using the SN65HVD257 in a Redundant Physical Layer CAN Network
Topology
CAN is a standard linear bus topology using 120-Ω twisted-pair cabling. The SN65HVD257 CAN device includes
several features to use the CAN physical layer in nonstandard topologies with only one CAN link layer controller
(μP) interface. This allows much greater flexibility in the physical topology of the bus while reducing the digital
controller and software costs. The combination of RXD DTO and the FAULT output allows great flexibility,
control, and monitoring of these applications.
A simple example of this flexibility is to use two SN65HVD257 devices in parallel with an AND gate to achieve
redundancy (parallel) of the physical layer (cabling and PHYs) in a CAN network.
For the CAN bit-wise arbitration to work, the RXD outputs of the transceivers must connect through AND gate
logic so that a dominant bit (low) from any of the branches is received by the link layer logic (μP) and appears to
the link layer and above as a single physical network. The RXD DTO feature prevents a bus stuck dominant fault
in a single branch from taking down the entire network by forcing the RXD pin for the transceivers on the branch
with the fault back to the recessive after the tRXD_DTO time. The remaining branch of the network continues to
function. The FAULT pin of the transceivers on the branch with the fault indicates this through the FAULT output
to their host processors, which diagnose the failure condition. The S pin (silent mode pin) may be used to put a
branch in silent mode to check each branch for other faults. Therefore, it is possible to implement a robust and
redundant CAN network topology in a very simple and low-cost manner.
These concepts can be expanded into more complicated and flexible CAN network topologies to solve various
system-level challenges with a networked infrastructure.
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Typical Applications (continued)
μP
μP
SN65HVD 257
A1
~~
~
~
SN65HVD 257
B1
RX D_A
RXD_B
SN65HVD 257
A2
RX D
TXD
S_A
FAULT_ A
S_B
RX D_A
RXD_B
SN65HVD 257
B2
FAULT_ B
RX D
SN65HVD 257
A3
TXD
S_A
FAULT_ A
S_B
SN65 HVD 257
B3
RX D_A
RXD_B
RXD_A
RXD_B
SN65 HVD257
An
FAULT_ B
RX D
TXD
S_A
FAULT_ A
S_B
FAULT_ B
RXD
TXD
S_A
FAULT_A
S_B
FAULT_B
SN65HVD 257
Bn
μP
μP
A.
CAN nodes with termination are PHY A, PHY B, PHY An and PHY Bn.
B.
RXD DTO prevents a single branch-stuck-dominant condition from blocking the redundant branch through the AND
logic on RXD. The transceivers signal a received bus stuck dominant fault through the FAULT pin. The system
detects which branch is stuck dominant and issues a system warning. Other network faults on a single branch that
appear as recessive (not blocking the redundant network) may be detected through diagnostic routines and using the
Silent Mode of the PHYs to use only one branch at a time for transmission during diagnostic mode. This combination
allows robust fault detection and recovery within single branches so that they may be repaired and again provide
redundancy of the physical layer.
Figure 20. Typical Redundant Physical Layer Topology Using the SN65HVD257 Device
10.2.1.3 Application Curves
Figure 21 shows the typical loop delay through the transceiver based on the differential resistive load between
CANH and CANL.
Figure 21. Typical TXD to RXD Loop Delay
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Typical Applications (continued)
10.2.2 Typical 3.3-V Microcontroller Application
The SN65HVD256 device has a second supply voltage pin used for level shifting the input and output pins. This
can be used for applications where there is a 3.3-V micrcontroller and a 5-V CAN transceiver.
VIN
VIN
VOUT
5-V Voltage
Regulator
(e.g. TPSxxxx)
VCC
VCC
3
Port x
S
SN65HVD256
CAN Transceiver
VOUT
RXD
3-V Voltage
Regulator
(e.g. TPSxxxx)
CANH
8
3-V MCU
VIN
7
TXD
RXD
TXD
4
1
5
VRXD
6
2
CANL
GND
Figure 22. Typical 3.3-V Application
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SLLSEA2D – DECEMBER 2011 – REVISED MAY 2015
11 Power Supply Recommendations
To ensure reliable operation at all data rates and supply voltages, each supply must be decoupled with a 100-nF
ceramic capacitor located as close as possible to the supply pins. The TPS76350 device is a linear voltage
regulator suitable for the 5-V supply rail.
12 Layout
12.1 Layout Guidelines
For the PCB design to be successful, start with the design of the protection and filtering circuitry because ESD
and EFT transients have a wide frequency bandwidth from approximately 3-MHz to 3-GHz and high frequency
layout techniques must be applied during PCB design. On chip IEC ESD protection is good for laboratory and
portable equipment but is usually not sufficient for EFT and surge transients occurring in industrial environments.
Therefore, robust and reliable bus node design requires the use of external transient protection devices at the
bus connectors. Placement at the connector also prevents these harsh transient events from propagating further
into the PCB and system.
Use VCC and ground planes to provide low inductance.
NOTE
High frequency current follows the path of least inductance and not the path of least
resistance.
Design the bus protection components in the direction of the signal path. Do not force the transient current to
divert from the signal path to reach the protection device. Below is a list of layout recommendations when
designing a CAN transceiver into an application.
• Transient Protection on CANH and CANL: Transient Voltage Suppression (TVS) and capacitors (D1, C5
and C7 shown in Figure 23) can be used to protect the system level transients like EFT, IEC ESD, and
Surge. These devices must be placed as close to the connector as possible. This prevents the transient
energy and noise from penetrating into other nets on the board.
• Bus Termination on CANH and CANL: Figure 23 shows split termination where the termination is split into
two resistors, R5 and R6, with the center or split tap of the termination connected to ground through capacitor
C6. Split termination provides common mode filtering for the bus. When termination is placed on the board
instead of directly on the bus, care must be taken to ensure the terminating node is not removed from the
bus, as this causes signal integrity issues if the bus is not properly terminated on both ends.
• Decoupling Capacitors on VCC and VRXD: Bypass and bulk capacitors must be placed as close as possible
to the supply pins of transceiver (examples are C2, C3, C5, and C6).
• Ground and power connections: Use at least two vias for VCC, VIO, and ground connections of bypass
capacitors and protection devices to minimize trace and via inductance.
• Digital inputs and outputs: To limit current of digital lines, serial resistors may be used. Examples are R1,
R2, R3, R4, and R5.
• Filtering noise on digital inputs and outputs: To filter noise on the digital I/O lines, a capacitor may be
used close to the input side of the I/O as shown by C1 and C4.
• External pull-up resistors on input and output pins: Because the internal pullup and pulldown biasing of
the device is weak for floating pins, an external 1-kΩ to 10-kΩ pullup or pulldown resistor must be used to
bias the state of the pins during transient events.
• Fault Output Pin (SN65HVD257 only): Because the FAULT output pin is an open drain output, an external
pullup resistor is required to pull the pin voltage high for normal operation (R5).
• VRXD Supply (SN65HVD256 only): The SN65HVD256 device will need additional bypass capacitors for the
VRXD supply shown with C5 and C6.
• TXD input pin: If an open-drain host processor is used to drive the TXD pin of the device, an external pullup
resistor between 1 kΩ and 10 kΩ must be used to help drive the recessive input state of the device (weak
internal pullup resistor).
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12.2 Layout Example
S
R2
GND
C4
TXD
R4
R1
8
1
C1
VCC orVRXD
C8
GND
GND
2
C7
SN65HVD25x
6
4
5
R8
C9
3
J1
D1
U1
C3
C2
VCC
R7
7
U1
GND
RXD
R3
VRXD
C6
C5
GND
R5
R6
FAULT
VCC or VRXD
Figure 23. Layout Example
13 Device and Documentation Support
13.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 7. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
SN65HVD255
Click here
Click here
Click here
Click here
Click here
SN65HVD256
Click here
Click here
Click here
Click here
Click here
SN65HVD257
Click here
Click here
Click here
Click here
Click here
13.2 Trademarks
All trademarks are the property of their respective owners.
13.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
13.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
14 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
SN65HVD255D
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD255
SN65HVD255DR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD255
SN65HVD256D
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD256
SN65HVD256DR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD256
SN65HVD257D
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD257
SN65HVD257DR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HVD257
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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