DS90LV804_07 Datasheet, PDF (5/10 Pages) National Semiconductor (TI) – 4-Channel 800 Mbps LVDS Buffer/Repeater

Feature Descriptions
INTERNAL TERMINATIONS
The DS90LV804 has integrated termination resistors on both
the input and outputs. The inputs have a 100Ω resistor across
the differential pair, placing the receiver termination as close
as possible to the input stage of the device. The LVDS outputs
also contain an integrated 100Ω ohm termination resistor, this
resistor is used to reduce the effects of Near End Crosstalk
(NEXT) and does not take the place of the 100 ohm termina-
tion at the inputs to the receiving device. The integrated
terminations improve signal integrity and decrease the exter-
nal component count resulting in space savings.
OUTPUT CHARACTERISTICS
The output characteristics of the DS90LV804 have been op-
timized for point-to-point backplane and cable applications,
and are not intended for multipoint or multidrop signaling.
TRI-STATE MODE
The EN input activates a hardware TRI-STATE mode. When
the TRI-STATE mode is active (EN=L), all input and output
buffers and internal bias circuitry are powered off and dis-
abled. Outputs are tri-stated in TRI-STATE mode. When ex-
iting TRI-STATE mode, there is a delay associated with
turning on bandgap references and input/output buffer circuits
as indicated in the LVDS Output Switching Characteristics
INPUT FAILSAFE BIASING
External pull up and pull down resistors may be used to pro-
vide enough of an offset to enable an input failsafe under
open-circuit conditions. This configuration ties the positive
LVDS input pin to V_DD 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 approxi-
mately 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” for more information.
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