SN75DP130: AUX_SRC+, AUX_SRC- are not connected

Hiroaki Yuyama TED

Part Number: SN75DP130

Tool/software:

Dear, support team.

One of our distributor's customers is using SN75DP130. In the TI recommended circuit, the AUX_SRC+ and AUX_SRC- lines are connected to the GPU.
However, the customer's AUX_SRC+ and AUX_SRC- are not connected to either.

Is there any difference in DisplayPort link training when the AUX_SRC line is connected to the GPU and when it is not connected?
Are there any other problems that can be considered when AUX_SRC is not connected?

SN75DP130_Customer Circuit.pdf

Best Regards,
Hiroaki Yuyama

View online

11 months ago

0 David (ASIC) Liu 11 months ago

TI__Guru**** 176721 points

Yuyama-san

In this case, DP130 is only monitoring the D3 power state transitions of the sink.

The AUX_SRCP/N, SCL_DDC, SDA_DDC, and CAD_SRC pins should be left unconnected and the CAD_SNK pin should be pulled down to ground.

The DP130’s link training feature must be disabled. This is done by writing a zero to DP130’s LINK_TRAINING_ENABLE bit (address 0x04 bit 2).

Thanks

David

0 Hiroaki Yuyama TED 11 months ago in reply to David (ASIC) Liu

Expert 1720 points

Hi,David-san

Thank you for your reply.
I will reply to the customer with your advice.

Best Regards,
Hiroaki Yuyama

0 Hiroaki Yuyama TED 11 months ago in reply to Hiroaki Yuyama TED

Expert 1720 points

Hello,David-san
Thank you for your advice.

I have provided your response as feedback to the customer.
The customer may have had a different understanding of the operating specifications of link training.

Please let me confirm two points to make sure our understanding is correct with the customer's.

Q1: If the AUX_SRC line is not connected as per the customer's design circuit, will all the register values in Table 4 of the SN75DP130 data sheet be invalid except for SET_POWER?
"Table 4. DPCD Registers Used by the SN75DP130 AUX Monitor"

Q2: When LINK_TRAINING_ENABLE=1, will the GPU's PRE-EMPHASIS and VOLTAGE_SWING be changed by control from the SN75DP130 in the attached system diagram?

Best Regards,
Hiroaki Yuyama

0 Vishesh Pithadiya 11 months ago in reply to Hiroaki Yuyama TED

TI__Mastermind 38505 points

Hey,

In the case of the customer circuit. It seems that the DP130 will be snooping the AUX circuitry through the AUXSNK pins.

When snooping the AUX, the DPCD registers should be able to be set automatically via link training.

The DP SINKs VOLTAGE-SWING and PRE-EMPHASIS settings will be sent to the DP130 as well as the GPU.

0 Hiroaki Yuyama TED 11 months ago in reply to Vishesh Pithadiya

Expert 1720 points

Hello, Vishesh-san

Thank you for your reply and answer.

I have fed your response back to the customer on the customer circuit.
If the customer responds again, please advise.

Best Regards,
Hiroaki Yuyama

0 Vishesh Pithadiya 11 months ago in reply to Hiroaki Yuyama TED

TI__Mastermind 38505 points

Sounds good, no problem!

0 Vishesh Pithadiya 11 months ago in reply to Vishesh Pithadiya

TI__Mastermind 38505 points

Hi,

I'm closing this thread due to inactivity

0 Hiroaki Yuyama TED 11 months ago in reply to Vishesh Pithadiya

Expert 1720 points

Hello, Vishesh-san

Please close this as we have no further questions from the customer.
Thank you for your interaction.

Best Regards,
Hiroaki Yuyama

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SN75DP130: AUX_SRC+, AUX_SRC- are not connected