GS8000 Datasheet, PDF (9/16 Pages) Gennum Corporation – DVI / HDMI Extender

3. Detailed Description
GS8000 Data Sheet
3.1 Differential Inputs
The GS8000 contains four current mode differential signal input buffers. These
allow the device to be connected to a DVI 1.0 compliant data stream consisting of
three transition minimized differential signals (TMDS) and a clock signal at one
tenth the data rate.
All input buffers have internal user programmable input termination pull-up
resistors. A resistor value of 500Ω should be connected between the EXT_RES pin
and D_GND to set the input termination to 50Ω.
The input buffers use a separate power supply of +3.3V DC (VDD and GND) and
have a wide common mode operating point.
3.2 LONG REACH™ DVI / HDMI
3.2.1 LONG REACH™ TMDS
Gennum’s patented DVI technology restores the received signals to the input level
defined in the DVI 1.0 and HDMI 1.1 specifications.
Four gain stages are provided, three of which extend TMDS data at rates from
250Mb/s to 1.65Gb/s. The fourth gain stage is optimized to extend the clock signal
at one tenth the received TMDS data rate.
These stages operate under the assumption that the input signal was launched at
an amplitude of between 800mV and 1200mV differential.
3.2.2 LONG REACH™ DDC
The DDC Extend block manages DDC traffic in both directions by restoring
incoming signals and boosting outgoing signals to meet the DDC specification.
Connect the DDC_SDA and DDC_SCL pins to the DDC bus at the closest location
to the GS8000. See Figure 3-2: LONG REACH™ DVI or HDMI Receive Solution.
NOTE: If a level shifter is necessary, the GS8000 must be placed on the 5V side
(connector side) as shown in Figure 3-2: LONG REACH™ DVI or HDMI Receive
Solution.
NOTE: The 5V present on the DVI and HDMI connectors can be significantly
reduced over long ranges of cable. Therefore, it is recommended that this voltage
not be used as the supply voltage for the LONG REACH™ DDC.
Proprietary and Confidential 25544 - 3 May 2005
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