DS90CR287 Datasheet, PDF (11/15 Pages) National Semiconductor (TI) – +3.3V Rising Edge Data Strobe LVDS 28-Bit Channel Link-85 MHZ

AC Timing Diagrams (Continued)
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 10) + ISI (Inter-symbol interference)(Note 11)
Cable Skew — typically 10 ps–40 ps per foot, media dependent
Note 10: Cycle-to-cycle jitter is less than 150ps at 85MHZ.
Note 11: ISI is dependent on interconnect length; may be zero
FIGURE 17. Receiver LVDS Input Skew Margin
DS101087-20
Applications Information
The DS90CR287 and DS90CR288A are backward compat-
ible 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 V_CC, LVDS V_CC and PLL V_CC.
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. However, the 5V/66 MHz
receiver maintain the outputs in the previous state when
powerdown occurred.
DS90CR287 Pin Description — Channel Link Transmitter
Pin Name
TxIN
TxOUT+
TxOUT−
TxCLK IN
TxCLK OUT+
TxCLK OUT−
PWR DWN
V_CC
GND
PLL V_CC
PLL GND
LVDS V_CC
LVDS GND
I/O No.
I
28
O
4
O
4
I
1
O
1
O
1
I
1
I
4
I
5
I
1
I
2
I
1
I
3
Description
TTL level input.
Positive LVDS differential data output.
Negative LVDS differential data output.
TTL IeveI clock input. The rising edge acts as data strobe. Pin name TxCLK IN.
Positive LVDS differential clock output.
Negative LVDS differential clock output.
TTL level input. Assertion (low input) TRI-STATES the outputs, ensuring low current at
power down.
Power supply pins for TTL inputs.
Ground pins for TTL inputs.
Power supply pin for PLL.
Ground pins for PLL.
Power supply pin for LVDS outputs.
Ground pins for LVDS outputs.
DS90CR288A Pin Description — Channel Link Receiver
Pin Name
RxIN+
RxIN−
RxOUT
RxCLK IN+
RxCLK IN−
RxCLK OUT
I/O No.
I
4
I
4
O 28
I
1
I
1
O
1
Description
Positive LVDS differential data inputs.
Negative LVDS differential data inputs.
TTL level data outputs.
Positive LVDS differential clock input.
Negative LVDS differential clock input.
TTL level clock output. The rising edge acts as data strobe. Pin name RxCLK OUT.
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