NSC DS90CR287 3.3v rising edge data strobe lvds 28-bit channel link-85 mhz Datasheet

DS90CR287/DS90CR288A
+3.3V Rising Edge Data Strobe LVDS 28-Bit Channel
Link-85 MHz
General Description
Features
The DS90CR287 transmitter converts 28 bits of LVCMOS/
LVTTL data into four LVDS (Low Voltage Differential Signaling) data streams. A phase-locked transmit clock is transmitted in parallel with the data streams over a fifth LVDS link.
Every cycle of the transmit clock 28 bits of input data are
sampled and transmitted. The DS90CR288A receiver converts the four LVDS data streams back into 28 bits of
LVCMOS/LVTTL data. At a transmit clock frequency of 85
MHz, 28 bits of TTL data are transmitted at a rate of 595
Mbps per LVDS data channel. Using a 85 MHz clock, the
data throughput is 2.38 Gbit/s (297.5 Mbytes/sec).
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This chipset is an ideal means to solve EMI and cable size
problems associated with wide, high-speed TTL interfaces.
20 to 85 MHz shift clock support
50% duty cycle on receiver output clock
2.5 / 0 ns Set & Hold Times on TxINPUTs
Low power consumption
± 1V common-mode range (around +1.2V)
Narrow bus reduces cable size and cost
Up to 2.38 Gbps throughput
Up to 297.5 Mbytes/sec bandwidth
345 mV (typ) swing LVDS devices for low EMI
PLL requires no external components
Rising edge data strobe
Compatible with TIA/EIA-644 LVDS standard
Low profile 56-lead TSSOP package
Block Diagrams
DS90CR288A
DS90CR287
10108727
10108701
Order Number DS90CR287MTD
See NS Package Number MTD56
© 2004 National Semiconductor Corporation
DS101087
Order Number DS90CR288AMTD
See NS Package Number MTD56
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DS90CR287/DS90CR288A +3.3V Rising Edge Data Strobe LVDS 28-Bit Channel Link-85 MHz
July 2004
DS90CR287/DS90CR288A
Pin Diagram for TSSOP Packages
DS90CR287
DS90CR288A
10108721
10108722
Typical Application
10108723
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2
Package Derating:
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VCC)
−0.5V to (VCC + 0.3V)
CMOS/TTL Output Voltage
−0.3V to (VCC + 0.3V)
LVDS Receiver Input Voltage
−0.3V to (VCC + 0.3V)
LVDS Driver Output Voltage
−0.3V to (VCC + 0.3V)
+150˚C
Storage Temperature
−65˚C to +150˚C
> 7kV
> 700V
(EIAJ, 0Ω, 200pF)
Latch Up Tolerance @
+25˚C
> ± 300mA
Recommended Operating
Conditions
Continuous
Junction Temperature
12.4 mW/˚C above +25˚C
(HBM, 1.5kΩ, 100pF)
LVDS Output Short Circuit
Duration
12.5 mW/˚C above +25˚C
DS90CR288AMTD
ESD Rating
−0.3V to +4V
CMOS/TTL Input Voltage
DS90CR287MTD
Min Nom Max Units
Supply Voltage (VCC)
Lead Temperature
(Soldering, 4 sec.)
3.0
+260˚C
Temperature (TA)
Solder Reflow Temperature
Receiver Input Range
Maximum Package Power Dissipation @ +25˚C
1.63 W
DS90CR288AMTD
1.61 W
3.6
V
−10 +25 +70
˚C
0
2.4
Supply Noise Voltage
(VCC)
MTD56 (TSSOP) Package:
DS90CR287MTD
3.3
Operating Free Air
V
100 mVPP
Electrical Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified
Symbol
Parameter
Conditions
Min
Typ
Max
Units
LVCMOS/LVTTL DC SPECIFICATIONS
VIH
High Level Input Voltage
2.0
VCC
V
VIL
Low Level Input Voltage
GND
0.8
V
VOH
High Level Output Voltage
IOH = −0.4 mA
VOL
Low Level Output Voltage
IOL = 2 mA
VCL
Input Clamp Voltage
ICL = −18 mA
IIN
Input Current
VIN = 0.4V, 2.5V or VCC
VIN = GND
IOS
Output Short Circuit Current
2.7
−10
VOUT = 0V
3.3
V
0.06
0.3
V
−0.79
−1.5
V
+1.8
+15
µA
−60
−120
mA
290
450
mV
35
mV
0
µA
LVDS DRIVER DC SPECIFICATIONS
VOD
Differential Output Voltage
∆VOD
Change in VOD between
Complimentary Output States
VOS
Offset Voltage (Note 4)
∆VOS
Change in VOS between
Complimentary Output States
IOS
Output Short Circuit Current
VOUT = 0V, RL = 100Ω
IOZ
Output TRI-STATE Current
PWR DWN = 0V, VOUT = 0V or VCC
RL = 100Ω
250
1.125
1.25
1.375
V
35
mV
−3.5
−5
mA
±1
± 10
µA
LVDS RECEIVER DC SPECIFICATIONS
VTH
Differential Input High Threshold
VTL
Differential Input Low Threshold
IIN
Input Current
VCM = +1.2V
+100
−100
VIN = +2.4V, VCC = 3.6V
VIN = 0V, VCC = 3.6V
3
mV
mV
± 10
± 10
µA
µA
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DS90CR287/DS90CR288A
Absolute Maximum Ratings (Note 1)
DS90CR287/DS90CR288A
Electrical Characteristics
(Continued)
Over recommended operating supply and temperature ranges unless otherwise specified
Symbol
Parameter
Conditions
Min
Typ
Max
Units
f = 33 MHz
31
45
mA
f = 40 MHz
32
50
mA
f = 66 MHz
37
55
mA
f = 85 MHz
42
60
mA
10
55
µA
f = 33 MHz
49
70
mA
f = 40 MHz
53
75
mA
f = 66 MHz
81
114
mA
f = 85 MHz
96
135
mA
PWR DWN = Low
Receiver Outputs Stay Low during
Powerdown Mode
140
400
µA
TRANSMITTER SUPPLY CURRENT
ICCTW
ICCTZ
Transmitter Supply Current Worst
Case (with Loads)
Transmitter Supply Current Power
Down
RL = 100Ω,
CL = 5 pF,
Worst Case
Pattern
(Figures 1, 2)
PWR DWN = Low
Driver Outputs in TRI-STATE
under Powerdown Mode
RECEIVER SUPPLY CURRENT
ICCRW
ICCRZ
Receiver Supply Current Worst
Case
CL = 8 pF,
Worst Case
Pattern
(Figures 1, 3)
Receiver Supply Current Power
Down
Note 1: “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. The tables of “Electrical Characteristics” specify conditions for device operation.
Note 2: Typical values are given for VCC = 3.3V and TA = +25˚C.
Note 3: 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 VOD and ∆VOD).
Note 4: VOS previously referred as VCM.
Transmitter Switching Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified
Typ
Max
LLHT
Symbol
LVDS Low-to-High Transition Time (Figure 2)
0.75
1.5
ns
LHLT
LVDS High-to-Low Transition Time (Figure 2)
0.75
1.5
ns
TCIT
TxCLK IN Transition Time (Figure 4)
6.0
ns
TPPos0
Transmitter Output Pulse Position for Bit0 (Figure 14)
−0.20
0
0.20
ns
TPPos1
Transmitter Output Pulse Position for Bit1
1.48
1.68
1.88
ns
TPPos2
Transmitter Output Pulse Position for Bit2
3.16
3.36
3.56
ns
TPPos3
Transmitter Output Pulse Position for Bit3
4.84
5.04
5.24
ns
TPPos4
Transmitter Output Pulse Position for Bit4
6.52
6.72
6.92
ns
TPPos5
Transmitter Output Pulse Position for Bit5
8.20
8.40
8.60
ns
TPPos6
Transmitter Output Pulse Position for Bit6
9.88
10.08
10.28
ns
TCIP
TxCLK IN Period (Figure 5 )
11.76
T
50
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
TSTC
TxIN Setup to TxCLK IN (Figure 5)
THTC
TxIN Hold to TxCLK IN (Figure 5)
TCCD
TxCLK IN to TxCLK OUT Delay (Figure 7)
TPLLS
TPDD
TJIT
TxCLK IN Cycle-to-Cycle Jitter (Input clock requirement)
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Parameter
Min
1.0
f = 85 MHz
f = 85 MHz
TA = 25˚C,
VCC = 3.3V
Units
2.5
ns
0
ns
6.3
ns
Transmitter Phase Lock Loop Set (Figure 9)
10
ms
Transmitter Powerdown Delay (Figure 12)
100
ns
2
ns
4
3.8
Over recommended operating supply and temperature ranges unless otherwise specified
Symbol
Parameter
CLHT
CMOS/TTL Low-to-High Transition Time (Figure 3)
CHLT
CMOS/TTL High-to-Low Transition Time (Figure 3)
RSPos0
Receiver Input Strobe Position for Bit 0 (Figure 15)
RSPos1
RSPos2
Min
Typ
Max
Units
2
3.5
ns
1.8
3.5
ns
0.49
0.84
1.19
ns
Receiver Input Strobe Position for Bit 1
2.17
2.52
2.87
ns
Receiver Input Strobe Position for Bit 2
3.85
4.20
4.55
ns
RSPos3
Receiver Input Strobe Position for Bit 3
5.53
5.88
6.23
ns
RSPos4
Receiver Input Strobe Position for Bit 4
7.21
7.56
7.91
ns
RSPos5
Receiver Input Strobe Position for Bit 5
8.89
9.24
9.59
ns
RSPos6
Receiver Input Strobe Position for Bit 6
10.57
10.92
11.27
ns
RSKM
RxIN Skew Margin (Note 5) (Figure 16)
RCOP
RxCLK OUT Period (Figure 6)
11.76
T
50
ns
RCOH
RxCLK OUT High Time (Figure 6)
4
5
6.5
ns
5
6
f = 85 MHz
f = 85 MHz
f = 85 MHz
290
ps
RCOL
RxCLK OUT Low Time (Figure 6)
3.5
RSRC
RxOUT Setup to RxCLK OUT (Figure 6)
3.5
ns
ns
RHRC
RxOUT Hold to RxCLK OUT (Figure 6)
3.5
ns
5.5
RCCD
RxCLK IN to RxCLK OUT Delay @ 25˚C, VCC = 3.3V (Note 6)(Figure 8)
9.5
ns
RPLLS
Receiver Phase Lock Loop Set (Figure 10)
10
ms
RPDD
Receiver Powerdown Delay (Figure 13)
1
µs
7
Note 5: Receiver Skew Margin is defined as the valid data sampling region at the receiver inputs. This margin takes into account the transmitter pulse positions (min
and max) and the receiver input setup and hold time (internal data sampling window-RSPOS). This margin allows LVDS interconnect skew, inter-symbol interference
(both dependent on type/length of cable), and source clock (less than 150 ps).
Note 6: Total latency for the channel link chipset is a function of clock period and gate delays through the transmitter (TCCD) and receiver (RCCD). The total latency
for the 217/287 transmitter and 218/288A receiver is: (T + TCCD) + (2*T + RCCD), where T = Clock period.
AC Timing Diagrams
10108702
FIGURE 1. “Worst Case” Test Pattern
5
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DS90CR287/DS90CR288A
Receiver Switching Characteristics
DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108703
10108704
FIGURE 2. DS90CR287 (Transmitter) LVDS Output Load and Transition Times
10108705
10108706
FIGURE 3. DS90CR288A (Receiver) CMOS/TTL Output Load and Transition Times
10108707
FIGURE 4. DS90CR287 (Transmitter) Input Clock Transition Time
10108709
FIGURE 5. DS90CR287 (Transmitter) Setup/Hold and High/Low Times
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DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108710
FIGURE 6. DS90CR288A (Receiver) Setup/Hold and High/Low Times
10108711
FIGURE 7. DS90CR287 (Transmitter) Clock In to Clock Out Delay
10108712
FIGURE 8. DS90CR288A (Receiver) Clock In to Clock Out Delay
10108713
FIGURE 9. DS90CR287 (Transmitter) Phase Lock Loop Set Time
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DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108714
FIGURE 10. DS90CR288A (Receiver) Phase Lock Loop Set Time
10108716
FIGURE 11. 28 Parallel TTL Data Inputs Mapped to LVDS Outputs
10108717
FIGURE 12. Transmitter Powerdown Delay
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DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108718
FIGURE 13. Receiver Powerdown Delay
10108719
FIGURE 14. Transmitter LVDS Output Pulse Position Measurement
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DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108728
FIGURE 15. Receiver LVDS Input Strobe Position
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DS90CR287/DS90CR288A
AC Timing Diagrams
(Continued)
10108720
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) + Source Clock Jitter (cycle to cycle)(Note 7) + ISI (Inter-symbol interference)(Note 8)
Cable Skew — typically 10 ps–40 ps per foot, media dependent
Note 7: Cycle-to-cycle jitter is less than 150ps at 85MHz.
Note 8: ISI is dependent on interconnect length; may be zero
FIGURE 16. Receiver LVDS Input Skew Margin
DS90CR287 MTD56 (TSSOP) Package Pin Description — Channel Link
Transmitter
Pin Name
I/O
No.
Description
TxIN
I
28
TTL level input.
TxOUT+
O
4
Positive LVDS differential data output.
TxOUT−
O
4
Negative LVDS differential data output.
TxCLK IN
I
1
TTL level clock input. The rising edge acts as data strobe. Pin name TxCLK IN. See
Applications Information section.
TxCLK OUT+
O
1
Positive LVDS differential clock output.
TxCLK OUT−
O
1
Negative LVDS differential clock output.
PWR DOWN
I
1
TTL level input. Assertion (low input) TRI-STATES the outputs, ensuring low current at
power down. See Applications Information section.
VCC
I
4
Power supply pins for TTL inputs.
GND
I
5
Ground pins for TTL inputs.
PLL VCC
I
1
Power supply pin for PLL.
PLL GND
I
2
Ground pins for PLL.
LVDS VCC
I
1
Power supply pin for LVDS outputs.
LVDS GND
I
3
Ground pins for LVDS outputs.
DS90CR288A MTD56 (TSSOP) Package Pin Description — Channel Link
Receiver
Pin Name
RxIN+
I/O
No.
I
4
Description
Positive LVDS differential data inputs.
RxIN−
I
4
Negative LVDS differential data inputs.
RxOUT
O
28
TTL level data outputs.
RxCLK IN+
I
1
Positive LVDS differential clock input.
RxCLK IN−
I
1
Negative LVDS differential clock input.
RxCLK OUT
O
1
TTL level clock output. The rising edge acts as data strobe. Pin name RxCLK OUT.
PWR DOWN
I
1
TTL level input. When asserted (low input) the receiver outputs are low.
VCC
I
4
Power supply pins for TTL outputs.
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DS90CR287/DS90CR288A
DS90CR288A MTD56 (TSSOP) Package Pin Description — Channel Link
Receiver (Continued)
Pin Name
I/O
No.
GND
I
5
PLL VCC
I
1
Power supply for PLL.
PLL GND
I
2
Ground pin for PLL.
LVDS VCC
I
1
Power supply pin for LVDS inputs.
LVDS GND
I
3
Ground pins for LVDS inputs.
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Description
Ground pins for TTL outputs.
12
The TSSOP version of the DS90CR287 and DS90CR288A
are backward compatible with the existing 5V Channel Link
transmitter/receiver pair (DS90CR283, DS90CR284). To upgrade from a 5V to a 3.3V system the following must be
addressed:
1. Change 5V power supply to 3.3V. Provide this supply to
the VCC, LVDS VCC and PLL VCC.
2.
Transmitter input and control inputs except 3.3V TTL/
CMOS levels. They are not 5V tolerant.
3. The receiver powerdown feature when enabled will lock
receiver output to a logic low.
The Channel Link devices are intended to be used in a wide
variety of data transmission applications. Depending upon
the application the interconnecting media may vary. For
example, for lower data rate (clock rate) and shorter cable
lengths ( < 2m), the media electrical performance is less
critical. For higher speed/long distance applications the media’s performance becomes more critical. Certain cable constructions provide tighter skew (matched electrical length
between the conductors and pairs). Additional applications
information can be found in the following National Interface
Application Notes:
AN = ####
RECEIVER FAILSAFE FEATURE: These receivers have
input failsafe bias circuitry to guarantee a stable receiver
output for floating or terminated receiver inputs. Under these
conditions receiver inputs will be in a HIGH state. If a clock
signal is present, data outputs will all be HIGH; if the clock
input is also floating/terminated, data outputs will remain in
the last valid state. A floating/terminated clock input will
result in a HIGH clock output.
BOARD LAYOUT: To obtain the maximum benefit from the
noise and EMI reductions of LVDS, attention should be paid
to the layout of differential lines. Lines of a differential pair
should always be adjacent to eliminate noise interference
from other signals and take full advantage of the noise
canceling of the differential signals. The board designer
should also try to maintain equal length on signal traces for
a given differential pair. As with any high-speed design, the
impedance discontinuities should be limited (reduce the
numbers of vias and no 90 degree angles on traces). Any
discontinuities which do occur on one signal line should be
mirrored in the other line of the differential pair. Care should
be taken to ensure that the differential trace impedance
match the differential impedance of the selected physical
media (this impedance should also match the value of the
termination resistor that is connected across the differential
pair at the receiver’s input). Finally, the location of the
CHANNEL LINK TxOUT/RxIN pins should be as close as
possible to the board edge so as to eliminate excessive pcb
runs. All of these considerations will limit reflections and
crosstalk which adversely effect high frequency performance
and EMI.
INPUTS: The TxIN and control pin inputs are compatible
with LVTTL and LVCMOS levels. This pins are not 5V tolerant.
UNUSED INPUTS: All unused inputs at the TxIN inputs of
the transmitter may be tied to ground or left no connect. All
unused outputs at the RxOUT outputs of the receiver must
then be left floating.
TERMINATION: Use of current mode drivers requires a
terminating resistor across the receiver inputs. The CHANNEL LINK chipset will normally require a single 100Ω resistor
between the true and complement lines on each differential
pair of the receiver input. The actual value of the termination
resistor should be selected to match the differential mode
characteristic impedance (90Ω to 120Ω typical) of the cable.
Figure 17 shows an example. No additional pull-up or pulldown resistors are necessary as with some other differential
technologies such as PECL. Surface mount resistors are
recommended to avoid the additional inductance that accompanies leaded resistors. These resistors should be
placed as close as possible to the receiver input pins to
reduce stubs and effectively terminate the differential lines.
DECOUPLING CAPACITORS: Bypassing capacitors are
needed to reduce the impact of switching noise which could
limit performance. For a conservative approach three
parallel-connected decoupling capacitors (Multi-Layered Ce-
Topic
AN-1041
Introduction to Channel Link
AN-1108
Channel Link PCB and Interconnect
Design-In Guidelines
AN-806
Transmission Line Theory
AN-905
Transmission Line Calculations and
Differential Impedance
AN-916
Cable Information
CABLES: A cable interface between the transmitter and
receiver needs to support the differential LVDS pairs. The
21-bit CHANNEL LINK chipset (DS90CR217/218A) requires
four pairs of signal wires and the 28-bit CHANNEL LINK
chipset (DS90CR287/288A) requires five pairs of signal
wires. The ideal cable/connector interface would have a
constant 100Ω differential impedance throughout the path. It
is also recommended that cable skew remain below 140ps
(@ 85 MHz clock rate) to maintain a sufficient data sampling
window at the receiver.
In addition to the four or five cable pairs that carry data and
clock, it is recommended to provide at least one additional
conductor (or pair) which connects ground between the
transmitter and receiver. This low impedance ground provides a common-mode return path for the two devices.
Some of the more commonly used cable types for point-topoint applications include flat ribbon, flex, twisted pair and
Twin-Coax. All are available in a variety of configurations and
options. Flat ribbon cable, flex and twisted pair generally
perform well in short point-to-point applications while TwinCoax is good for short and long applications. When using
ribbon cable, it is recommended to place a ground line
between each differential pair to act as a barrier to noise
coupling between adjacent pairs. For Twin-Coax cable applications, it is recommended to utilize a shield on each
cable pair. All extended point-to-point applications should
also employ an overall shield surrounding all cable pairs
regardless of the cable type. This overall shield results in
improved transmission parameters such as faster attainable
speeds, longer distances between transmitter and receiver
and reduced problems associated with EMS or EMI.
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DS90CR287/DS90CR288A
The high-speed transport of LVDS signals has been demonstrated on several types of cables with excellent results.
However, the best overall performance has been seen when
using Twin-Coax cable. Twin-Coax has very low cable skew
and EMI due to its construction and double shielding. All of
the design considerations discussed here and listed in the
supplemental application notes provide the subsystem communications designer with many useful guidelines. It is recommended that the designer assess the tradeoffs of each
application thoroughly to arrive at a reliable and economical
cable solution.
Applications Information
DS90CR287/DS90CR288A
Applications Information
traces for power and ground and ensure each capacitor has
its own via to the ground plane. If board space is limiting the
number of bypass capacitors, the PLL VCC should receive
the most filtering/bypassing. Next would be the LVDS VCC
pins and finally the logic VCC pins.
(Continued)
ramic type in surface mount form factor) between each VCC
and the ground plane(s) are recommended. The three capacitor values are 0.1 µF, 0.01 µF and 0.001 µF. An example
is shown in Figure 18. The designer should employ wide
10108724
FIGURE 17. LVDS Serialized Link Termination
10108725
FIGURE 18. CHANNEL LINK
Decoupling Configuration
data transmission. LVDS supports an input voltage range of
Ground to +2.4V. This allows for a ± 1.0V shifting of the
center point due to ground potential differences and
common-mode noise.
TRANSMITTER INPUT CLOCK: The transmitter input clock
must always be present when the device is enabled (PWR
DOWN = HIGH). If the clock is stopped, the PWR DOWN pin
must be used to disable the PLL. The PWR DOWN pin must
be held low until after the input clock signal has been reapplied. This will ensure a proper device reset and PLL lock to
occur.
POWER SEQUENCING AND POWERDOWN MODE: Outputs of the CHANNEL LINK transmitter remain in TRI-STATE
until the power supply reaches 2V. Clock and data outputs
will begin to toggle 10 ms after VCC has reached 3V and the
Powerdown pin is above 1.5V. Either device may be placed
into a powerdown mode at any time by asserting the Powerdown pin (active low). Total power dissipation for each
device will decrease to 5 µW (typical).
The transmitter input clock may be applied prior to powering
up and enabling the transmitter. The transmitter input clock
may also be applied after power up; however, the use of the
PWR DOWN pin is required as described in the Transmitter
CLOCK JITTER: The CHANNEL LINK devices employ a
PLL to generate and recover the clock transmitted across the
LVDS interface. The width of each bit in the serialized LVDS
data stream is one-seventh the clock period. For example, a
85 MHz clock has a period of 11.76 ns which results in a data
bit width of 1.68 ns. Differential skew (∆t within one differential pair), interconnect skew (∆t of one differential pair to
another) and clock jitter will all reduce the available window
for sampling the LVDS serial data streams. Care must be
taken to ensure that the clock input to the transmitter be a
clean low noise signal. Individual bypassing of each VCC to
ground will minimize the noise passed on to the PLL, thus
creating a low jitter LVDS clock. These measures provide
more margin for channel-to-channel skew and interconnect
skew as a part of the overall jitter/skew budget.
INPUT CLOCK: The input clock should be present at all
times when the part in enabled. If the clock is stopped, the
PWR DOWN pin should be asserted to disable the PLL.
Once the clock is active again, the part can then be enabled.
Do not enable the part without a clock present.
COMMON-MODE vs. DIFFERENTIAL MODE NOISE MARGIN: The typical signal swing for LVDS is 300 mV centered
at +1.2V. The CHANNEL LINK receiver supports a 100 mV
threshold therefore providing approximately 200 mV of differential noise margin. Common-mode protection is of more
importance to the system’s operation due to the differential
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receiver. If power to the transmit board is lost, the receiver
clocks (input and output) stop. The data outputs (RxOUT)
retain the states they were in when the clocks stopped.
When the receiver board loses power, the receiver inputs are
shorted to VCC through an internal diode. Current is limited
(5 mA per input) by the fixed current mode drivers, thus
avoiding the potential for latchup when powering the device.
(Continued)
Input Clock section. Do not power up and enable (PWR
DOWN = HIGH) the transmitter without a valid clock signal
applied to the TxCLK IN pin.
The CHANNEL LINK chipset is designed to protect itself
from accidental loss of power to either the transmitter or
10108726
FIGURE 19. Single-Ended and Differential Waveforms
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DS90CR287/DS90CR288A
Applications Information
DS90CR287/DS90CR288A +3.3V Rising Edge Data Strobe LVDS 28-Bit Channel Link-85 MHz
Physical Dimensions
inches (millimeters)
unless otherwise noted
56-Lead Molded Thin Shrink Small outline Package, JEDEC
Order Number DS90CR287MTD or DS90CR288AMTD
Dimensions shown in millimeters only
NS Package Number MTD56
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification
(CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.