DS90LV804_16 Datasheet, PDF (5/15 Pages) Texas Instruments – 4-Channel 800 Mbps LVDS Buffer/Repeater

DS90LV804
www.ti.com
SNLS195L – SEPTEMBER 2005 – REVISED APRIL 2013
APPLICATION INFORMATION
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 termination at the
inputs to the receiving device. The integrated terminations improve signal integrity and decrease the external
component count resulting in space savings.
OUTPUT CHARACTERISTICS
The output characteristics of the DS90LV804 have been optimized 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 disabled. Outputs are tri-stated in TRI-STATE
mode. When exiting 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 provide 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 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” for more information.
INPUT INTERFACING
The DS90LV804 accepts differential signals and allow simple AC or DC coupling. With a wide common mode
range, the DS90LV804 can be DC-coupled with all common differential drivers (that is, LVPECL, LVDS, CML).
Figure 2, Figure 3, and Figure 4 illustrate typical DC-coupled interface to common differential drivers. Note that
the DS90LV804 inputs are internally terminated with a 100Ω resistor.
LVDS
Driver
OUT+
100: Differential T-Line
IN+
DS90LV804
Receiver
100:
OUT-
IN-
Figure 2. Typical LVDS Driver DC-Coupled Interface to DS90LV804 Input
Copyright © 2005–2013, Texas Instruments Incorporated
Product Folder Links: DS90LV804
Submit Documentation Feedback
5