DS90LV028AQ_14 Datasheet, PDF (6/16 Pages) Texas Instruments – Automotive LVDS Dual Differential Line Receiver

DS90LV028AQ, DS90LV028AQ-Q1
SNLS299E – MAY 2008 – REVISED APRIL 2013
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INPUT FAILSAFE BIASING
External pull up and pull down resistors may be used to provide enough of an offset to enable an input failsafe
under open-circuit conditions. This configuration ties the positive LVDS input pin to VDD thru a pull up resistor
and the negative LVDS input pin is tied to GND by a pull down resistor. The pull up and pull down resistors
should be in the 5kΩ to 15kΩ range to minimize loading and waveform distortion to the driver. The common-
mode bias point ideally should be set to approximately 1.2V (less than 1.75V) to be compatible with the internal
circuitry. Please refer to application note AN-1194, “Failsafe Biasing of LVDS Interfaces” (SNLA051)for more
information.
PROBING LVDS TRANSMISSION LINES
Always use high impedance (> 100kΩ), low capacitance (< 2 pF) scope probes with a wide bandwidth (1 GHz)
scope. Improper probing will give deceiving results.
CABLES AND CONNECTORS, GENERAL COMMENTS
When choosing cable and connectors for LVDS it is important to remember:
Use controlled impedance media. The cables and connectors you use should have a matched differential
impedance of about 100Ω. They should not introduce major impedance discontinuities.
Balanced cables (e.g. twisted pair) are usually better than unbalanced cables (ribbon cable, simple coax) for
noise reduction and signal quality. Balanced cables tend to generate less EMI due to field canceling effects and
also tend to pick up electromagnetic radiation a common-mode (not differential mode) noise which is rejected by
the receiver.
For cable distances < 0.5M, most cables can be made to work effectively. For distances 0.5M ≤ d ≤ 10M, CAT 3
(category 3) twisted pair cable works well, is readily available and relatively inexpensive.
Pin Number
1, 4
2, 3
6, 7
8
5
Name
R_IN-
R_IN+
R_OUT
V_CC
GND
PIN DESCRIPTIONS
Inverting receiver input pin
Non-inverting receiver input pin
Receiver output pin
Power supply pin, +3.3V ± 0.3V
Ground pin
Description
6
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