SN75DP130: How to manage unused pin

user4999529

Part Number: SN75DP130

Hi Team

If we don't need to TMDS or DP++ operation, SDA_DDC(pin34), SCL_DDC(pin33), CAD_SNK(10), CAD_SRC(8) are not connected is OK?

We only use this device as an eDP re-driver. (internally wiring only)

Thanks

Best regards,

Kawai

over 6 years ago

0 David (ASIC) Liu over 6 years ago

TI__Guru**** 177396 points

Kawai-san

CAD_SNK needs to pulled to GND through a 100k resistor. SDA_DDC, SCL_DDC, and CAD_SRC can left floating.

What is the application? Is this a source or a sink application?

Thanks
David

0 user4999529 over 6 years ago in reply to David (ASIC) Liu

Prodigy 130 points

David-san

Thank you, I will change our hardware to be pulled up (CAD_SNK).

This is used for a 5.4Gbps eDP redriver. This is a source application.

Thanks
Kawai

0 user4999529 over 6 years ago in reply to user4999529

Prodigy 130 points

David-san

pulled up --> pulled down

Thanks
Kawai

0 user4999529 over 6 years ago in reply to user4999529

Prodigy 130 points

David-san

I saw datasheet. 1M resister is recommended as described below.
[An external 1MΩ resistor to GND is recommended.]

Which (1M or 100k) is better?

Thanks
Kawai

0 David (ASIC) Liu over 6 years ago in reply to user4999529

TI__Guru**** 177396 points

Kawai-san

1M is assuming the CAD_SNK signal is driven by the DP sink, so we use 1M to keep CAD_SNK from floating when it is not driven by the DP sink.

100k is assuming the CAD_SNK signal is not driven by the DP sink.

Thanks
David

0 user4999529 over 6 years ago in reply to David (ASIC) Liu

Prodigy 130 points

David-san

>1M is assuming the CAD_SNK signal is driven by the DP sink.

>100k is assuming the CAD_SNK signal is not driven by the DP sink.

Our system use DP only, not use TMDS mode. Therefore, is 1M better for our system?

Thanks

Kawai

0 David (ASIC) Liu over 6 years ago in reply to user4999529

TI__Guru**** 177396 points

Kawai-san

CAD_SNK is typically connected to CONFIG1 pin (pin 13) of the DP connector, and then you have the 1M pulldown on CAD_SNK.

Thanks
David

0 user4999529 over 6 years ago in reply to David (ASIC) Liu

Prodigy 130 points

David-san

Thank you for your reply.
Do you confirm below?

If SN75 connect to DP interface(DP connector), CAD_SNK is typically connected to CONFIG1 pin (pin 13) with 1M pulldown.
If SN75 connect to eDP interface, CAD_SNK should be pull down at 100k. <--this is our system

Is this right?

Thanks
Kawai

0 David (ASIC) Liu over 6 years ago in reply to user4999529

TI__Guru**** 177396 points

Kawai-san

This is ok.

Thanks
David

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SN75DP130: How to manage unused pin