TMDS171 datasheet(28/63 Pages) TI2

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VOD(SS) = 1020mVpp

VOD(PP) = 1200mVpp

st bit

nd to N bit

PRE_SEL = Z

Vsadj = 7.06<Q

I2C Reg0Ch[7:5] = 011

Reg0C[1:0] = 01

TMDS171, TMDS171I

SLLSEN7E – OCTOBER 2015 – REVISED SEPTEMBER 2017

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Figure 29. Pre-emphasis Using I2C

8.4 Device Functional Modes

8.4.1 Retimer Mode

Clock and Data Recovery Circuits (CDR) are used to track, sample and retime the equalized data bit streams.

The CDRs are designed with loop bandwidth to minimize the amount of jitter transfer from the video source to

the TMDS outputs. Input jitter within the CDR’s PLL bandwidth, < 1 MHz, is transferred to the TMDS outputs.

Higher frequency jitter above the CDR loop bandwidth is attenuated, providing a jitter cleaning function to reduce

the amount of high frequency jitter from the video source. The retimer is automatically activated at pixel clock

above approximately 100 MHz when jitter cleaning is needed for robust operation. The retimer operates at about

100 Mhz – 340 MHz pixel clock (1 – 3.4 Gbps). At pixel clock below about 100 MHz, the TMDS171 automatically

bypasses the internal retimer, and operates as a redriver. When the video source changes resolution, the internal

retimer starts the acquisition process to determine the input clock frequency and acquire lock to the new data bit

streams. During the clock frequency detection period and the retimer acquisition period that last approximately 7

ms, the TMDS drivers can be kept active (default) or programmed to be disabled to avoid sending invalid clock or

data to the downstream receiver. The TMDS171 can support retimer mode across the full data rate range of 250

Mbps - 3.4 Gbps by setting DEV_FUNC_MODE bits at reg0Ah[1:0], See Table 9. For compliance testing such as

JTOL for 480 Mbps the PLL must be forced to lock.

8.4.2 Redriver Mode

The TMDS171 can function as a redriver which compensates for ISI channel loss. In this mode, power is

reduced as the CDR and PLL are turned off. When in automatic mode, the TMDS171 is in redriver mode for data

rates < 1.0 Gbps. By using I2C the device can be put in Redriver mode for the complete data range of 250 Mbps

to 3.4 Gbps. This is done by writing a 00 to register 0Ah[1:0]. If the link has excessive random jitter then retimer

mode is the best operating mode. If the link has excessive random jitter, the retimer mode is the best operating

mode. When in redriver mode, the device compensates for ISI loss only. When in redriver mode compliance is

not ensured as skew compensation and retiming functions are disabled. If a significant amount of random jitter is

present, the system may not pass compliance at the connector.

TMDS171 Datasheet(PDF) 28 Page - Texas Instruments