TDP142: Connection of SNOOPENZ pin and CONFIG1 at Dual mode

masahiko shimizu

Part Number: TDP142
Other Parts Discussed in Thread: SN74AHC1G125

Hi,

My customer doesn't use snooping function and use Dual mode and GPIO mode.
At this time, Does my customer need to connect SNOOPENZ pin and CONFIG1 thru a buffer?
My customer will pull SNOOPENZ to "High" in their board for not using snooping function.

Best regards,
Shimizu

over 5 years ago

0 David (ASIC) Liu over 5 years ago

TI__Guru*** 139405 points

Shimizu-san

When supporting DP++, with TDP142 configured in GPIO mode (I2C_EN = 0), the SNOOPENZ pin must be connected to the CONFIG1 pin on DisplayPort receptacle through a buffer like the SN74AHC1G125. The buffer is required because the internal pulldown on SNOOPENZ pin is too strong to register a valid VIH when a Dual mode adapter is plugged into the DisplayPort receptacle.

Thanks
David

0 masahiko shimizu over 5 years ago in reply to David (ASIC) Liu

Guru 11235 points

Hi David-san,

Thank you for your previous support
I add a question.

If we want to support DP++, AUXp/n should be connected to GPU with Dual mode support?
(=>Should we use AUXp/n for supporting DP++?)

Best regards,
Shimizu

0 David (ASIC) Liu over 5 years ago in reply to masahiko shimizu

TI__Guru*** 139405 points

Shimizu-san

It depends on the snooping function implementation. If you don't plan to use snooping function, then the DisplayPort AUXP/N signals can bypass the TDP142. When bypassing the TDP142 AUXP/N pins, the AUXN pin should be pulled up to 3.3V through 100K resistor and the AUXP pin should be pulled down to GND through a 100K resistor.

Thanks
David

0 masahiko shimizu over 5 years ago in reply to David (ASIC) Liu

Guru 11235 points

Hi David-san,

Thank you for your previous support.
I add a question about SNOOPENZ pin.

I think CONFIG1 is signal for detecting connection of HDMI device at supporting DP++.
TDP142 is recommended to connect SNOOPENZ and CONFIG1 even if snoop function isn't used.
Could you let me know the reason of connection of SNOOPENZ pin, please?

Best regards,
Shimizu

0 David (ASIC) Liu over 5 years ago in reply to masahiko shimizu

TI__Guru*** 139405 points

Shimizu-san

SNOOPENZ only needs to be connected to CONFIG1 through a buffer if dual mode DisplayPort is required. If not, SNOOPENZ can be pulled high or low depending on whether AUX snoop is needed or not.

Thanks
David

0 masahiko shimizu over 5 years ago in reply to David (ASIC) Liu

Guru 11235 points

Hi David-san,

Thank you for your replay.
I have understood above your answer from your previous post.

I want to know why SNOOPEN need to connect CONFIG1 at using Dual mode.

Best regards,
Shimizu

0 David (ASIC) Liu over 5 years ago in reply to masahiko shimizu

TI__Guru*** 139405 points

Shimizu-san

You don't have to connect SNOOPENz to CONFIG1, connect SNOOPENz to CONFIG1 is for power saving when you are in DP mode. If SNOOPENz is connected to CONFIG1, when in HDMI mode, SNOOPENz will be high and AUX snoop is disabled since HDMI is always 4 lanes. When in DP mode, SNOOPENz will be low, which enables AUX snoop, and certain lanes can be turned off depending on the AUX traffic, therefore save you the power.

Thanks
David

0 masahiko shimizu over 5 years ago in reply to David (ASIC) Liu

Guru 11235 points

Hi David-san,

Thank you for your support.
But I got confused.
I re-question to you.

If my customer uses this device at Dual mode with GPIO mode, But they doesn't use snooping function.
Does my customer need to connect SNOOPENZ pin and CONFIG1 thru a buffer?

Best regards,
Shimizu

0 David (ASIC) Liu over 5 years ago in reply to masahiko shimizu

TI__Guru*** 139405 points

Shimizu-san

No, you can tie SNOOPENZ pin to 3.3V through a resistor to disable the SNOOP function.

Thanks
David

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TDP142: Connection of SNOOPENZ pin and CONFIG1 at Dual mode