DS90CR481, DS90CR482
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SNLS137D – NOVEMBER 2000 – REVISED APRIL 2013
DS90CR481 / DS90CR482 48-Bit LVDS Channel Link SER/DES − 65 - 112 MHz
Check for Samples: DS90CR481, DS90CR482
FEATURES
1
•
•
•
•
2
•
•
•
•
•
•
•
•
3.168 Gbits/sec Bandwidth with 66 MHz Clock
5.376 Gbits/sec Bandwidth with 112 MHz Clock
65 - 112 MHz Input Clock Support
LVDS SER/DES Reduces Cable and Connector
Size
Pre-Emphasis Reduces Cable Loading Effects
Optional DC Balance Encoding Reduces ISI
Distortion
Cable Deskew of +/−1 LVDS Data Bit Time (up
to 80 MHz Clock Rate)
5V Tolerant TxIN and Control Input Pins
Flow Through Pinout for Easy PCB Design
+3.3V Supply Voltage
Transmitter Rejects Cycle-to-Cycle Jitter
Conforms to ANSI/TIA/EIA-644-1995 LVDS
Standard
DESCRIPTION
The DS90CR481 transmitter converts 48 bits of
CMOS/TTL data into eight LVDS (Low Voltage
Differential Signaling) data streams. A phase-locked
transmit clock is transmitted in parallel with the data
streams over a ninth LVDS link. Every cycle of the
transmit clock 48 bits of input data are sampled and
transmitted. The DS90CR482 receiver converts the
LVDS data streams back into 48 bits of
LVCMOS/TTL data. At a transmit clock frequency of
112MHz, 48 bits of TTL data are transmitted at a rate
of 672Mbps per LVDS data channel. Using a 112MHz
clock,
the
data
throughput
is
5.38Gbit/s
(672Mbytes/s). At a transmit clock frequency of
112MHz, 48 bits of TTL data are transmitted at a rate
of 672Mbps per LVDS data channel. Using a 66MHz
clock, the data throughput is 3.168Gbit/s
(396Mbytes/s).
The multiplexing of data lines provides a substantial
cable reduction. Long distance parallel single-ended
buses typically require a ground wire per active signal
(and have very limited noise rejection capability).
Thus, for a 48-bit wide data and one clock, up to 98
conductors are required. With this Channel Link
chipset as few as 19 conductors (8 data pairs, 1 clock
pair and a minimum of one ground) are needed. This
provides an 80% reduction in cable width, which
provides a system cost savings, reduces connector
physical size and cost, and reduces shielding
requirements due to the cables' smaller form factor.
The 48 CMOS/TTL inputs can support a variety of
signal combinations. For example, 6 8-bit words or 5
9-bit (byte + parity) and 3 controls.
The DS90CR481/DS90CR482 chipset is improved
over prior generations of Channel Link devices and
offers higher bandwidth support and longer cable
drive with three areas of enhancement. To increase
bandwidth, the maximum clock rate is increased to
112 MHz and 8 serialized LVDS outputs are
provided. Cable drive is enhanced with a user
selectable pre-emphasis feature that provides
additional output current during transitions to
counteract cable loading effects. Optional DC
balancing on a cycle-to-cycle basis, is also provided
to reduce ISI (Inter-Symbol Interference). With preemphasis and DC balancing, a low distortion eyepattern is provided at the receiver end of the cable. A
cable deskew capability has been added to deskew
long cables of pair-to-pair skew of up to +/−1 LVDS
data bit time (up to 80 MHz Clock Rate). These three
enhancements allow cables 5+ meters in length to be
driven.
The chipset is an ideal means to solve EMI and cable
size problems associated with wide, high speed TTL
interfaces.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2000–2013, Texas Instruments Incorporated
DS90CR481, DS90CR482
SNLS137D – NOVEMBER 2000 – REVISED APRIL 2013
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Generalized Block Diagrams (DS90CR481 and DS90CR482)
Generalized Transmitter Block Diagram – DS90CR481
Generalized Receiver Block Diagram – DS90CR482
2
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SNLS137D – NOVEMBER 2000 – REVISED APRIL 2013
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.
Absolute Maximum Ratings (1) (2)
Value
Unit
−0.3 to +4
V
−0.3 to +5.5
V
LVCMOS/TTL Output Voltage
−0.3 to (VCC + 0.3)
V
LVDS Receiver Input Voltage
−0.3 to +3.6
V
LVDS Driver Output Voltage
−0.3 to +3.6
V
Supply Voltage (VCC)
CMOS/TTL Input Voltage
LVDS Output Short Circuit Duration
Continuous
Junction Temperature
+150
°C
Storage Temperature
−65 to +150
°C
Lead Temperature (Soldering, 4 sec.) 100L TQFP
+260
°C
Maximum Package Power Dissipation Capacity @ 25°C, 100 TQFP
Package:
DS90CR481VJD
2.3
W
DS90CR482VS
2.3
W
Package Derating:
DS90CR481VJD
18.1mW/°C above
+25°C
DS90CR482VS
18.1mW/°C above
+25°C
ESD Rating: DS90CR481
(HBM, 1.5kΩ, 100pF)
>6
(EIAJ, 0Ω, 200pF)
ESD Rating: DS90CR482
(HBM, 1.5kΩ, 100pF)
(EIAJ, 0Ω, 200pF)
(1)
kV
> 300
V
>2
kV
> 200
V
“Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to
imply that the device should be operated at these limits. “Electrical Characteristics” specify conditions for device operation.
If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
(2)
Recommended Operating Conditions
Min
Nom
Max
Units
Supply Voltage (VCC)
3.0
3.3
3.6
V
Operating Free Air Temperature (TA)
−10
+25
+70
°C
100
mVp-p
112
MHz
Supply Noise Voltage
Input Clock (TX)
65
Electrical Characteristics (1)
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ (2)
Max
Units
CMOS/TTL DC SPECIFICATIONS
VIH
High Level Input Voltage
2.0
VIL
Low Level Input Voltage
GND
VOH
High Level Output Voltage IOH = −0.4 mA
IOH = −2mA
V
0.8
V
2.7
2.9
V
2.7
2.85
V
VOL
Low Level Output Voltage
IOL = 2 mA
0.1
0.3
VCL
Input Clamp Voltage
ICL = −18 mA
−0.79
−1.5
V
IIN
Input Current
VIN = 0.4V, 2.5V or VCC
+1.8
+15
µA
VIN = GND
(1)
(2)
−15
0
V
µA
Current into device pins is defined as positive. Current out of device pins is defined as negative. Voltages are referenced to ground
unless otherwise specified (except VTH, VTL, VOD and ΔVOD).
Typical values are given for VCC = 3.3V and T A = +25°C.
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Electrical Characteristics(1) (continued)
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
IOS
Parameter
Conditions
Output Short Circuit
Current
Min
Typ (2)
Max
Units
−120
mA
450
mV
35
mV
1.375
V
35
mV
−3.5
−5
mA
±1
±10
µA
+100
mV
VOUT = 0V
LVDS DRIVER DC SPECIFICATIONS
|VOD|
Differential Output Voltage RL = 100Ω
ΔVOD
Change in VOD between
Complimentary Output
States
VOS
Offset Voltage
ΔVOS
Change in VOS between
Complimentary Output
States
IOS
Output Short Circuit
Current
VOUT = 0V, RL = 100Ω
IOZ
Output TRI-STATE
Current
PD = 0V, VOUT = 0V or VCC
250
1.125
345
1.25
LVDS RECEIVER DC SPECIFICATIONS
VTH
Differential Input High
Threshold
VTL
Differential Input Low
Threshold
IIN
Input Current
VCM = +1.2V
−100
mV
VIN = +2.4V, VCC = 3.6V
±10
µA
VIN = 0V, VCC = 3.6V
±10
µA
TRANSMITTER SUPPLY CURRENT
ICCTW
ICCTZ
Transmitter Supply
Current
Worst Case
RL = 100Ω, CL = 5 pF,
BAL = High,
Worst Case Pattern
(Figure 1, Figure 2)
f = 66MHz
106
160
mA
f = 112MHz
155
210
mA
Transmitter Supply
Current
Power Down
PD = Low,
Driver Outputs in TRI-STATE during power down Mode
5
50
µA
f = 66MHz
200
210
mA
f = 112MHz
250
280
mA
20
100
µA
RECEIVER SUPPLY CURRENT
ICCRW
ICCRZ
Receiver Supply Current
Worst Case
CL = 8 pF, BAL = High,
Worst Case Pattern
(Figure 1, Figure 3)
Receiver Supply Current
Power Down
PD = Low,
Receiver Outputs stay low during power down mode.
Recommended Transmitter Input Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Min
Typ
Max
Units
TCIT
Symbol
TxCLK IN Transition Time (Figure 4)
1.0
2.0
3.0
ns
TCIP
TxCLK IN Period (Figure 5)
8.93
15.38
ns
TCIH
TxCLK in High Time (Figure 5)
0.35T
0.5T
0.65T
ns
TCIL
TxCLK in Low Time (Figure 5)
0.35T
0.5T
0.65T
ns
TXIT
TxIN Transition Time
6.0
ns
4
Parameter
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SNLS137D – NOVEMBER 2000 – REVISED APRIL 2013
Transmitter Switching Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
LLHT
LHLT
Parameter
Min
Typ
Max
Units
LVDS Low-to-High Transition Time, (Figure 2),
PRE = 0.75V (disabled)
0.14
0.7
ns
LVDS Low-to-High Transition Time, (Figure 2),
PRE = Vcc (max)
0.11
0.6
ns
LVDS High-to-Low Transition Time, (Figure 2),
PRE = 0.75V (disabled)
0.16
0.8
ns
LVDS High-to-Low Transition Time, (Figure 2),
PRE = Vcc (max)
0.11
0.7
ns
TBIT
Transmitter Bit Width
f = 66 MHz,
112MHz
1/7 TCIP
TPPOS
Transmitter Pulse Positions - Normalized
f = 65 to 112
MHz
TJCC
Tranmitter Jitter - Cycle-to-Cycle
100
ps
TCCS
TxOUT Channel to Channel Skew
40
ps
TSTC
TxIN Setup to TxCLK IN, (Figure 5)
THTC
TxIN Hold to TxCLK IN, (Figure 5)
TPDL
Transmitter Propagation Delay - Latency, (Figure 7)
TPLLS
TPDD
− 200
0
ns
+200
2.5
ns
0
1.5(TCIP)+3.72
ps
ns
1.5(TCIP)+4.4
1.5(TCIP)+6.24
ns
Transmitter Phase Lock Loop Set, (Figure 9)
10
ms
Transmitter Powerdown Delay, (Figure 11)
100
ns
Receiver Switching Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
CLHT
CHLT
RCOP
RCOH
Max
Units
CMOS/TTL Low-to-High Transition Time, Rx data out,
(Figure 3)
Parameter
Min
2.0
ns
CMOS/TTL Low-to-High Transition Time, Rx clock out,
(Figure 3)
1.0
ns
CMOS/TTL High-to-Low Transition Time, Rx data out,
(Figure 3)
2.0
ns
CMOS/TTL High-to-Low Transition Time, Rx clock out,
(Figure 3)
1.0
ns
15.38
ns
RxCLK OUT Period, (Figure 6)
8.928
T
f = 112 MHz
3.5
ns
f = 66 MHz
6.0
ns
f = 112 MHz
3.5
ns
f = 66 MHz
6.0
ns
RxOUT Setup to RxCLK
OUT,(Figure 6)
f = 112 MHz
2.4
ns
f = 66 MHz
3.6
ns
RHRC
RxOUT Hold to RxCLK OUT,
(Figure 6), (1)
f = 112 MHz
3.4
ns
RPDL
Receiver Propagation Delay - Latency, (Figure 8)
RPLLS
RPDD
RCOL
RSRC
(1)
RxCLK OUT High Time, (Figure 6),
(1)
Typ
RxCLK OUT Low Time, (Figure 6),
(1)
f = 66 MHz
6.0
3(TCIP)+4.0
ns
3(TCIP)+4.8
3(TCIP)+6.5
ns
Receiver Phase Lock Loop Set, (Figure 10)
10
ms
Receiver Powerdown Delay, (Figure 12)
1
µs
The Minimum and Maximum Limits are based on statistical analysis of the device performance over voltage and temperature ranges.
This parameter is functionally tested on Automatic Test Equipment (ATE). ATE is limited to 85MHz. A sample of characterization parts
have been bench tested to verify functional performance.
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Chipset RSKM Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified. See APPLICATIONS
INFORMATION section (1) (2).
Symbol
RSKM
Parameter
Receiver Skew Margin without Deskew
in non-DC Balance Mode, (Figure 13),
(3)
RSKM
Receiver Skew Margin without Deskew
in DC Balance Mode, (Figure 13), (3)
RSKMD
Min
Typ
Max
Units
f = 112 MHz
170
f = 100 MHz
170
240
ps
f = 85MHz
300
350
ps
f = 66MHz
300
350
ps
f = 112 MHz
170
f = 100 MHz
170
200
ps
f = 85 MHz
250
300
ps
f = 66 MHz
250
300
ps
Receiver Skew Margin with Deskew in
DC Balance, (Figure 14),
f = 33 to 80 MHz
RDR
Receiver Deskew Range
f = 80 MHz
RDSS
Receiver Deskew Step Size
f = 80 MHz
ps
ps
0.25TBIT
ps
±1
TBIT
(4)
(1)
(2)
(3)
(4)
6
0.3 TBIT
ns
The Minimum and Maximum Limits are based on statistical analysis of the device performance over voltage and temperature ranges.
This parameter is functionally tested on Automatic Test Equipment (ATE). ATE is limited to 85MHz. A sample of characterization parts
have been bench tested to verify functional performance.
Typical values for RSKM and RSKMD are applicable for fixed VCC and T A of the Transmitter and Receiver (both are assumed to be at
the same VCC and T A points).
Receiver Skew Margin (RSKM) is defined as the valid data sampling region at the receiver inputs. This margin takes into account
transmitter output pulse positions (min and max) and the receiver input setup and hold time (internal data sampling window, RSPOS).
This margin allows for LVDS interconnect skew, inter-symbol interference (both dependent on type/length of cable) and clock jitter
(TJCC).RSKM ≥ cable skew (type, length) + source clock jitter (cycle to cycle,TJCC) + ISI (if any). See APPLICATIONS INFORMATION
section for more details.
Receiver Skew Margin with Deskew (RSKMD) is defined as the valid data sampling region at the receiver inputs. The DESKEW function
will constrain the receiver’s sampling strobes to the middle half of the LVDS bit and removes (adjusts for) fixed interconnect skew. This
margin (RSKMD) allows for inter-symbol interference (dependent on type/length of cable), Transmitter Pulse Position (TPPOS) variance,
and LVDS clock jitter (TJCC).RSKMD ≥ ISI + TPPOS(variance) + source clock jitter (cycle to cycle, TJCC). See APPLICATIONS
INFORMATION section for more details.
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AC Timing Diagrams
(1)
The worst case test pattern produces a maximum toggling of digital circuits, LVDS I/O and CMOS/TTL I/O.
Figure 1. “Worst Case” Test Pattern
Figure 2. DS90CR481 (Transmitter) LVDS Output Load and Transition Times
Figure 3. DS90CR482 (Receiver) CMOS/TTL Output Load and Transition Times
Figure 4. DS90CR481 (Transmitter) Input Clock Transition Time
Figure 5. DS90CR481 (Transmitter) Setup/Hold and High/Low Times
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Figure 6. DS90CR482 (Receiver) Setup/Hold and High/Low Times
Figure 7. DS90CR481 (Transmitter) Propagation Delay - Latency
Figure 8. DS90CR482 (Receiver) Propagation Delay - Latency
Figure 9. DS90CR481 (Transmitter) Phase Lock Loop Set Time
8
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Figure 10. DS90CR482 (Receiver) Phase Lock Loop Set Time
Figure 11. DS90CR481 (Transmitter) Power Down Delay
Figure 12. DS90CR482 (Receiver) Power Down Delay
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C—Setup and Hold Time (Internal data sampling window) defined by Rspos (receiver input strobe position) min and
max
Tppos—Transmitter output pulse position (min and max)
RSKM ≥ Cable Skew (type, length) + LVDS Source Clock Jitter (cycle to cycle) + ISI (Inter-symbol interference)
■ Cable Skew—typically 10 ps–40 ps per foot, media dependent
■ Cycle-to-cycle LVDS Output jitter (TJCC) is less than 100 ps (worse case estimate).
■ ISI is dependent on interconnect length; may be zero
See APPLICATIONS INFORMATION section for more details.
Figure 13. Receiver Skew Margin (RSKM) for Chipset without DESKEW
C — Setup and Hold Time (Internal data sampling window) defined by Rspos (receiver input strobe position) min and
max
RSKMD ≥ TPPOSvariance (d) + TJCC (output jitter)(f) + ISI (m)
■ d= Tppos—Transmitter output pulse position (min and max)
■ f= Cycle-to-cycle LVDS Output jitter (TJCC) is less than 100 ps (worse case estimate)
■ m= extra margin - assigned to ISI in long cable applications
See APPLICATIONS INFORMATION section for more details.
Figure 14. Receiver Skew Margin (RSKMD) for Chipset with DESKEW
10
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LVDS Interface
Optional features supported: Pre-emphasis and DESKEW
Figure 15. 48 Parallel TTL Data Bits Mapped to LVDS Bits with DC Balance Enabled
Optional feature supported: Pre-emphasis
Figure 16. 48 Parallel TTL Data Bits Mapped to LVDS Bits with DC Balance Disabled
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APPLICATIONS INFORMATION
The DS90CR481/DS90CR482 chipset is improved over prior generations of Channel Link devices and offers
higher bandwidth support and longer cable drive with three areas of enhancement. To increase bandwidth, the
maximum clock rate is increased to 112 MHz and 8 serialized LVDS outputs are provided. Cable drive is
enhanced with a user selectable pre-emphasis feature that provides additional output current during transitions to
counteract cable loading effects. This requires the use of one pull up resistor to Vcc; please refer to Table 1 to
set the level needed. Optional DC balancing on a cycle-to-cycle basis, is also provided to reduce ISI (InterSymbol Interference). With pre-emphasis and DC balancing, a low distortion eye-pattern is provided at the
receiver end of the cable. A cable deskew capability has been added to deskew long cables of pair-to-pair skew
of up to ±1 LVDS data bit time (up to 80 MHz clock rates). For details on deskew, refer to the Deskew section
below. These three enhancements allow cables 5+ meters in length to be driven depending upon media and
clock rate.
The DS90CR481/482 chipset may also be used in a non-DC Balance mode. In this mode pre-emphasis is
supported. In this mode, the chipset is also compatible with 21 and 28-bit Channel Link Receivers. See Figure 16
for the LVDS mapping.
NEW FEATURES DESCRIPTION
Pre-emphasis
Adds extra current during LVDS logic transition to reduce the cable loading effects. Pre-emphasis strength is set
via a DC voltage level applied from min to max (0.75V to Vcc) at the “PRE” pin. A higher input voltage on the
”PRE” pin increases the magnitude of dynamic current during data transition. The “PRE” pin requires one pull-up
resistor (Rpre) to Vcc in order to set the DC level. There is an internal resistor network, which cause a voltage
drop. Please refer to the tables below to set the voltage level.
The waveshape at the Receiver input should not exhibit over or undershoot with the proper amount of preemphasis set. Too much pre-emphasis generates excess noise and increases power dissipation. Cables less
than 2 meters in length typically do not require pre-emphasis.
Table 1. Pre-emphasis DC Voltage Level with (Rpre)
Rpre
Resulting PRE Voltage
Effect
1MΩ or NC
0.75V
Standard LVDS
50kΩ
1.0V
9kΩ
1.5V
3kΩ
2.0V
1kΩ
2.6V
100Ω
Vcc
50% pre-emphasis
100% pre-emphasis
Table 2. Pre-emphasis Needed per Cable Length (1)
(1)
Frequency
PRE Voltage
Typical cable length
112MHz
1.0V
2 meters
112MHz
1.5V
5 meters
80MHz
1.0V
2 meters
80MHz
1.2V
5+ meters
66MHz
1.5V
7 meters
This is based on testing with standard shield twisted pair cable. The amount of pre-emphasis will vary
depending on the type of cable, length and operating frequency.
DC Balance
In addition to data information an additional bit is transmitted on every LVDS data signal line during each cycle
as shown in Figure 15. This bit is the DC balance bit (DCBAL). The purpose of the DC Balance bit is to minimize
the short- and long-term DC bias on the signal lines. This is achieved by selectively sending the data either
unmodified or inverted.
12
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The value of the DC balance bit is calculated from the running word disparity and the data disparity of the current
word to be sent. The data disparity of the current word shall be calculated by subtracting the number of bits of
value 0 from the number of bits value 1 in the current word. Initially, the running word disparity may be any value
between +7 and −6. The running word disparity shall be calculated as a continuous sum of all the modified data
disparity values, where the unmodified data disparity value is the calculated data disparity minus 1 if the data is
sent unmodified and 1 plus the inverse of the calculated data disparity if the data is sent inverted. The value of
the running word disparity shall saturate at +7 and −6.
The value of the DC balance bit (DCBAL) shall be 0 when the data is sent unmodified and 1 when the data is
sent inverted. To determine whether to send data unmodified or inverted, the running word disparity and the
current data disparity are used. If the running word disparity is positive and the current data disparity is positive,
the data shall be sent inverted. If the running word disparity is positive and the current data disparity is zero or
negative, the data shall be sent unmodified. If the running word disparity is negative and the current data
disparity is positive, the data shall be sent unmodified. If the running word disparity is negative and the current
data disparity is zero or negative, the data shall be sent inverted. If the running word disparity is zero, the data
shall be sent inverted.
DC Balance mode is set when the BAL pin on the transmitter is tied HIGH - see pin descriptions. DC Balancing
is useful on long cable applications which are typically greater than 5 meters in length.
Deskew
Deskew is supported in the DC Balance mode only (BAL = high on DS90CR481). The “DESKEW” pin on the
receiver when set high will deskew a minimum of ±1 LVDS data bit time skew from the ideal strobe location
between signals arriving on independent differential pairs (pair-to-pair skew). It is required that the “DS_OPT” pin
on the Transmitter must be applied low for a minimum of four clock cycles to complete the deskew operation. It is
also required that this must be performed at least once at any time after the PLLs have locked to the input clock
frequency. If power is lost, or if the cable has been switched, this procedure must be repeated or else the
receiver may not sample the incoming LVDS data correctly. When the receiver is in the deskew mode, all
receiver outputs are set to a LOW state, but the receiver clock output is still active and switching. Setting the
“DESKEW” pin to low will disable the deskew operation and allow the receiver to operation on a fixed data
sampling strobe. In this case, the ”DS_OPT” pin on the transmitter must then be set high.
The DS_OPT pin at the input of the transmitter (DS90CR481) is used to initiate the deskew calibration pattern. It
must be applied low for a minimum of four clock cycles in order for the receiver to complete the deskew
operation. For this reason, the LVDS clock signal with DS_OPT applied high (active data sampling) shall be
1111000 or 1110000 pattern. During the deskew operation with DS_OPT applied low, the LVDS clock signal
shall be 1111100 or 1100000 pattern. The transmitter will also output a series of 1111000 or 1110000 onto the
LVDS data lines (TxOUT 0-7) during deskew so that the receiver can automatically calibrated the data sampling
strobes at the receiver inputs. Each data channel is deskewed independently and is tuned with a step size of 1/3
of a bit time over a range of +/−1 TBIT from the ideal strobe location. The Deskew feature operates up to clock
rates of 80 MHz only. If the Receiver is enabled in the deskew mode, then it must be trained before data transfer.
CLOCK JITTER
The transmitter is designed to reject cycle-to-cycle jitter which may be seen at the transmitter input clock. Very
low cycle-to-cycle jitter is passed on to the transmitter outputs. Cycle-to-cycle jitter has been measured over
frequency to be less than 100 ps with input step function jitter applied. This should be subtracted from the
RSKM/RSKMD budget as shown and described in Figure 13 and Figure 14. This rejection capability significantly
reduces the impact of jitter at the TXinput clock pin, and improves the accuracy of data sampling in the receiver.
Transmitter output jitter is effected by PLLVCC noise and input clock jitter - minimize supply noise and use a low
jitter clock source to limit output jitter. The falling edge of the input clock to the transmitter is the critical edge and
is used by the PLL circuit.
RSKM - RECEIVER SKEW MARGIN
RSKM is a chipset parameter and is explained in AN-1059 (SNLA050) in detail. It is the difference between the
transmitter’s pulse position and the receiver’s strobe window. RSKM must be greater than the summation of:
Interconnect skew, LVDS Source Clock Jitter (TJCC), and ISI (if any). See Figure 13. Interconnect skew includes
PCB traces differences, connector skew and cable skew for a cable application. PCB trace and connector skew
can be compensated for in the design of the system. Cable skew is media type and length dependant.
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RSKMD - RECEIVER SKEW MARGIN WITH DESKEW
RSKMD is a chipset parameter and is applicable when the DESKEW feature of the DS90CR482 is employed. It
is the difference between the receiver’s strobe window and the ideal pulse locations. The DESKEW feature
adjusts for skew between each data channel and the clock channel. This feature is supported up to 80MHz clock
rate. RSKMD must be greater than the summation of: Transmitter’s Pulse Position variance, LVDS Source Clock
Jitter (TJCC), and ISI (if any). See Figure 14. With DESKEW, RSKMD will be a minimum of 25% of TBIT.
Deskew compensates for interconnect skew which includes PCB traces differences, connector skew and cable
skew (for a cable application). PCB trace and connector skew can be compensated for in the design of the
system. Note, cable skew is media type and length dependant. Cable length may be limited by the RSKMD
parameter prior to the interconnect skew reaching 1 TBIT in length due to ISI effects.
POWER DOWN
Both transmitter and receiver provide a power down feature. When asserted current draw through the supply pins
is minimized and the PLLs are shut down. The transmitter outputs are in TRI-STATE when in power down mode.
The receiver outputs are forced to a active LOW state when in the power down mode. (See Table 3 and
Table 4). The PD pin should be driven HIGH to enable the device once VCC is stable.
CONFIGURATIONS
The transmitter is designed to be connected typically to a single receiver load. This is known as a point-to-point
configuration. It is also possible to drive multiple receiver loads if certain restrictions are made. Only the final
receiver at the end of the interconnect should provide termination across the pair. In this case, the driver still
sees the intended DC load of 100 Ohms. Receivers connected to the cable between the transmitter and the final
receiver must not load down the signal. To meet this system requirement, stub lengths from the line to the
receiver inputs must be kept very short.
CABLE TERMINATION
A termination resistor is required for proper operation to be obtained. The termination resistor should be equal to
the differential impedance of the media being driven. This should be in the range of 90 to 132 Ohms. 100 Ohms
is a typical value common used with standard 100 Ohm twisted pair cables. This resistor is required for control of
reflections and also to complete the current loop. It should be placed as close to the receiver inputs to minimize
the stub length from the resistor to the receiver input pins.
HOW TO CONFIGURE FOR BACKPLANE APPLICATIONS
In a backplane application with differential line impedance of 100Ω the differential line pair-to-pair skew can
controlled by trace layout. The transmitter-DS90CR481 “DS_OPT” pin may be set high. In a backplane
application with short PCB distance traces, pre-emphasis from the transmitter is typically not required. The “PRE”
pin should be left open (do not tie to ground). A resistor pad provision for a pull up resistor to Vcc can be
implemented in case pre-emphasis is needed to counteract heavy capacitive loading effects.
HOW TO CONFIGURE FOR CABLE INTERCONNECT APPLICATIONS
In applications that require the long cable drive capability. The DS90CR481/DS90CR482 chipset is improved
over prior generations of Channel Link devices and offers higher bandwidth support and longer cable drive with
the use of DC balanced data transmission, pre-emphasis. Cable drive is enhanced with a user selectable preemphasis feature that provides additional output current during transitions to counteract cable loading effects.
This requires the use of one pull up resistor to Vcc; please refer to Table 1 to set the level needed. Optional DC
balancing on a cycle-to-cycle basis, is also provided to reduce ISI (Inter-Symbol Interference) for long cable
applications. With pre-emphasis and DC balancing, a low distortion eye-pattern is provided at the receiver end of
the cable. These enhancements allow cables 5+ meters in length to be driven. Depending upon clock rate and
the media being driven, the cable Deskew feature may also be employed - see discussion on DESKEW, RSKM
and RSKMD above.
14
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SUPPLY BYPASS RECOMMENDATIONS
Bypass capacitors must be used on the power supply pins. Different pins supply different portions of the circuit,
therefore capacitors should be nearby all power supply pins except as noted in Table 3 and Table 4. Use high
frequency ceramic (surface mount recommended) 0.1µF capacitors close to each supply pin. If space allows, a
0.01µF capacitor should be used in parallel, with the smallest value closest to the device pin. Additional scattered
capacitors over the printed circuit board will improve decoupling. Multiple (large) via should be used to connect
the decoupling capacitors to the power plane. A 4.7 to 10 µF bulk cap is recommended near the PLLVCC pins
and also the LVDSVCC (pin #40) on the Transmitter. Connections between the caps and the pin should use wide
traces.
INPUT SIGNAL QUALITY REQUIREMENTS - TRANSMITTER
The input signal quality must comply to the datasheet requirements, please refer to the Recommended
Transmitter Input Characteristics table for specifications. In addition undershoots in excess of the ABS MAX
specifications are not recommended. If the line between the host device and the transmitter is long and acts as a
transmission line, then termination should be employed. If the transmitter is being driven from a device with
programmable drive strengths, data inputs are recommended to be set to a weak setting to prevent transmission
line effects. The clock signal is typically set higher to provide a clean edge that is also low jitter.
UNUSED LVDS OUTPUTS
Unused LVDS output channels should be terminated with 100 Ohm at the transmitter’s output pin.
LVDS INTERCONNECT GUIDELINES
See AN-1108 (SNLA008) and AN-905 (SNLA035) for full details.
• Use 100Ω coupled differential pairs
• Use the S/2S/3S rule in spacings
– S = space between the pair
– 2S = space between pairs
– 3S = space to TTL signal
• Minimize the number of VIA
• Use differential connectors when operating above 500Mbps line speed
• Maintain balance of the traces
• Minimize skew within the pair
• Minimize skew between pairs
• Terminate as close to the RXinputs as possible
RECEIVER OUTPUT DRIVE STRENGTH
The DS90CR482 output specify a 8pF load, VOH and VOL are tested at ± 2mA, which is intended for only 1 or
maybe 2 loads. If high fan-out is required or long transmission line driving capability, buffering the receiver output
is recommended. Receiver outputs do not support / provide a TRI-STATE function.
DS90CR483/484
The DS90CR481/2 chipset is electrically similar to the DS90CR483/4. The DS90CR481/2 differ only in the
control circuit of the internal PLL and are specified for 65 to 112 MHz operation. The devices will directly interoperate within the scope of the respective datasheets.
FOR MORE INFORMATION
Channel Link Applications Notes currently available:
• AN-1041 () Introduction to Channel Link
• AN-1059 (SNLA050) RSKM Calculations
• AN-1108 (SNLA008) PCB and Interconnect Guidelines
• AN-905 () Differential Impedance
• TI’s LVDS Owner’s Manual (literature number SNLA187)
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Table 3. DS90CR481 Pin Descriptions—Channel Link Transmitter
Pin Name
I/O
Description
(1)
TxIN
I
TTL level input.
TxOUTP
O
Positive LVDS differential data output.
TxOUTM
O
Negative LVDS differential data output.
TxCLKIN
I
TTL level clock input. The rising edge acts as data strobe.
TxCLKP
O
Positive LVDS differential clock output.
TxCLKM
O
Negative LVDS differential clock output.
PD
I
TTL level input. Assertion (low input) tri-states the outputs, ensuring low current at power down.
(1)
PLLSEL
I
PLL range select. This pin must be tied to VCC. NC or tied to Ground is reserved for future use.
(1)
PRE
I
Pre-emphasis “level” select. Pre-emphasis is active when input is tied to VCC through external pull-up
resistor. Resistor value determines Pre-emphasis level (See APPLICATIONS INFORMATION Section). For
normal LVDS drive level (No Pre-emphasis) leave this pin open (do not tie to ground).
DS_OPT
I
Cable Deskew performed when TTL level input is low. No TxIN data is sampled during Deskew. To
perform Deskew function, input must be held low for a minimum of 4 clock cycles. The Deskew operation is
normally conducted after the TX and RX PLLs have locked. It should also be conducted after a system
reset, or a reconfiguration event. It must be peformed at least once when "DESKEW" is enabled. (2)
BAL
I
TTL level input. This pin was previously labeled as VCC, which enabled the DC Balance function. But when
tied low or left open, the DC Balance function is disabled. Please refer to (Figure 15 Figure 16) for LVDS
data bit mapping respectively. (2), (3)
VCC
I
Power supply pins for TTL inputs and digital circuitry. Bypass not required on Pins 20 and 21.
GND
I
Ground pins for TTL inputs and digital circuitry.
PLLVCC
I
Power supply pin for PLL circuitry.
PLLGND
I
Ground pins for PLL circuitry.
LVDSVCC
I
Power supply pin for LVDS outputs.
LVDSGND
I
Ground pins for LVDS outputs.
NC
(1)
(2)
(3)
No Connect. Make NO Connection to these pins - leave open.
Inputs default to “low” when left open due to internal pull-down resistor.
Inputs default to “low” when left open due to internal pull-down resistor.
The DS90CR482 is design to automatically detect the DC Balance or non-DC Balance transmitted data from the DS90CR481 and
deserialize the LVDS data according to the define bit mapping.
Table 4. DS90CR482 Pin Descriptions—Channel Link Receiver (1)
Pin Name
I/O
Description
RxINP
I
Positive LVDS differential data inputs.
RxINM
I
Negative LVDS differential data inputs.
RxOUT
O
TTL level data outputs. In PowerDown (PD = Low) mode, receiver outputs are forced to a Low
state.
RxCLKP
I
Positive LVDS differential clock input.
RxCLKM
I
Negative LVDS differential clock input.
RxCLKOUT
O
TTL level clock output. The rising edge acts as data strobe.
PLLSEL
I
PLL range select. This pin must be tied to VCC. NC or tied to Ground is reserved for future use.
DESKEW
I
Deskew / Oversampling “on/off” select. When using the Deskew / Oversample feature this pin
must be tied to VCC. Tieing this pin to ground disables this feature. (2) Deskew is only supported in
the DC Balance mode.
PD
I
TTL level input. When asserted (low input) the receiver outputs are Low.
VCC
I
Power supply pins for TTL outputs and digital circuitry. Bypass not required on Pins 6 and 77.
GND
I
Ground pins for TTL outputs and digital circuitry.
PLLVCC
I
Power supply for PLL circuitry.
PLLGND
I
Ground pin for PLL circuitry.
(1)
(2)
16
(2)
(2)
These receivers have input fail-safe bias circuitry to guarantee a stable receiver output for floating or terminated receiver inputs. Under
test conditions receiver inputs will be in a HIGH state. If the cable interconnect (media) are disconnected which results in
floating/terminated inputs, the outputs will remain in the last valid state.
Inputs default to “low” when left open due to internal pull-down resistor.
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Table 4. DS90CR482 Pin Descriptions—Channel Link Receiver(1) (continued)
Pin Name
I/O
Description
LVDSVCC
I
Power supply pin for LVDS inputs.
LVDSGND
I
Ground pins for LVDS inputs.
NC
No Connect. Make NO Connection to these pins - leave open.
DS90DR481 — Connection Diagram
Figure 17. Transmitter - DS90CR481 - TQFP - Top View
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DS90CR481, DS90CR482
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DS90CR482 – Connection Diagram
Figure 18.
Figure 19. Receiver - DS90CR482 - TQFP - Top View
18
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SNLS137D – NOVEMBER 2000 – REVISED APRIL 2013
REVISION HISTORY
Changes from Revision C (April 2013) to Revision D
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 18
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PACKAGE OPTION ADDENDUM
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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)
(3)
Device Marking
(4/5)
(6)
DS90CR481VJD/NOPB
ACTIVE
TQFP
NEZ
100
90
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-10 to 70
DS90CR481VJD
>B
DS90CR482VS/NOPB
ACTIVE
TQFP
NEZ
100
90
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-10 to 70
DS90CR482VS
>B
DS90CR482VSX/NOPB
ACTIVE
TQFP
NEZ
100
1000
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-10 to 70
DS90CR482VS
>B
(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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