TMDS181RGZEVM: ESD Queries

Hi David,
Thanks alot.

By the way, another query on HDMI.

Product condition:
• HDMI2.0 and USB3.0 connector board, to connect host (CCD sensor) and sink (Monitor/PC), means to transfer the data from sensor to processor. So need to make sure the data rate is under requirement.
• HDMI/USB cable is about 3 meter from SENSOR to BOARD.

HDMI ? :
1. ?. for HDMI 5V, link it from HOST to SINK, need to ADD EXTRA 5V SUPPLY ?
2. ?: for REDRIVER/RETIMER, which mode is better or more fast for our condition?
• Redriver – only amp the signal and transmit
• Retimer – clean and new clock signal
3. ?: I2C control interface:
If no I2C interface, can setup the configure for Redriver /or Retimer mode at high data rate by GPIO (7 pins)? Any weakness for this way?

4. ?: from the reference design as SN65DP159, there are 1M ohm resistor and 0.01uF cap added between shield pin to Board GND, is only for ESD/EMI? Or it is must? How about use 0 ohm resistor or small solder pad to MAIN GND?
5. ?: DDC_SCL/SDA directly connect to SINK HDMI Output and TMDS181 chipset (SCL/SDA_SNK), I confuse for this application with different connection as below, do you have any idea?
• DDC_SCL/SDA(HOST)  TMDS181 (SCL/SDA_SNK) + SINK(DDC_SCL/SDA)
• DDC_SCL/SDA(HOST)  TMDS181 (SCL/SDA_SRC) ……. Then (TMDS181) SCL/SDA_SNK SINK(DDC_SCL/SDA)
6. ?: need to add AC Couple cap (0.1uF) for the data input from HOST (8 pins) ? what situation need to add?

Very appreciate for your help on these.

Thanks.

Shaun

1. This would depend on your system design requirement.
2. You can set the TMDS181 to automatically cross over from redriver to retimer mode depending on the data rate. Use of redriver/retimer depends on the overall system signal integrity and jitter performance.
3. Device would function in pin strap and I2C mode. I would recommend having the I2C as the second option in case device debugging is needed.
4. 1M and 0.01uF are used for ESD purpose. 1M provides a high impedance path between connector GND and board GND so the ESD events will not couple onto the board ESD, but discharge through the connector GND. But ESD design/requirement would depend on your system design requirement.
5. Both proposed approaches would work. Please note the TMDS181 utilizes clock stretching for DDC transactions. As there are sources and
sinks that do not perform this function correctly a system may not work correctly as DDC transactions are incorrectly transmitted/received. To overcome this a snoop configuration can be implemented where the SDA/SCL from the source is connected directly to the SDA/SCL sink as shown in your proposal #1.
6. This depends on technology/source/sink requirement. For example, HDMI 2.0 is a DC only interface (so no AC coupling caps are needed) while USB3.1 is a AC coupled interface (AC coupling caps are needed).

Thanks
David

Hi David,

On the Power supply 1.2V  for HDMI TMDS181: 

If I want to use DC/DC for the 1.2V, is there any issue for the EMC ? I am afraid the switching frequency affect the EMC.

if use the LDO, the Voltage drop is big, and the chip should be heat. (IDD max current = 350mA)

Any suggestion for this? Any DC/DC part recommend?

Thanks.

Shaun

Please take a look at TPS62150A, but it also depends on your voltage input requirement.

Thanks
David

Hi David,
For HDMI 2.0, I need to place the connector (IN & OUT) on the TOP layer, so must swap the signal lines, both for Lane and Polarity. Such as below:

So should configure the register to:
09H.bit7 = 1
09H.bit6 =1
So the TMDS181 is only be used as Retimer Mode.

Any recommend for above?

Thanks.