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SN75DP139: questions for reference design

K.Yaita
Guru 29720 points
Part Number: SN75DP139

Hi Team,

I got reference design schematic of SN75DP139 from Moises-san and was asked the following questions from my customer.
Could you support the following questions?

1)
My customer wants to bridge AUX+/- signal of display port to I2C signal of HDMI with SN75DP139.
I also heard the AUX+/- signal isn't DDC signal in this case.
Is it possible to achieve with SN75DP139?

2)
It seems R4(AUX_n_DP_SDA) and R5(AUX_p_DP_SCL) resistors aren't mounted in this reference design.
Could you tell me the specific case that R4 and R5 should be mounted?

3)
It seems R6(CAD_SINK_DP) resistor isn't mounted in this reference design.
Could you tell me the specific case that R6 should be mounted?

Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 23815 points

    Hi Yaita-san,

    DP139 is a level shifter, it takes DP++(HDMI AC coupled signals) and level shifts them to HDMI DC coupled signals. The DP139 won't do AUX to DDC conversion, the GPU will send DDC over AUX or DDC on a different port.

    It is strange that R4, R5, and R6 are there as placeholders, R6 is not mounted because any application using DP139 should work in DP++ mode.

    I'll send a different reference schematic which is clearer.

    Regards

  • 0 in reply to Moises Garcia
    Guru 29720 points

    Hi Moises-san,

    Thank you for your continuous support.
    I got your reference schematic on e-mail.

    >The DP139 won't do AUX to DDC conversion, the GPU will send DDC over AUX or DDC on a different port.
    Is it possible to use DP139 if DDC is sent over AUX (AUX+ / AUX-)?
    It seems DP139 doesn't support AUX+ / AUX- because pin name are "SDA_SOURCE" and "SCL_SOURCE".



    I heard AUX+ / AUX- (not DDC) are sent to DP139 in my customer's system and they wants to confirm if DP139 is usable in this case.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 23815 points
    Hi Yaita-san,

    If the source is DP++ and there is only AUX port in the GPU, the AUX channel will provide DDC voltage levels.
    If there are concerns, you can assert CAD signal in the GPU and take captures of AUX channel to see how it behaves when sending HDMI video.

    Regards
  • 0 in reply to Moises Garcia
    Guru 29720 points

    Hi Moises-san,

    Thank you for your advice. I apologize if it was elementary question..

    >If the source is DP++ and there is only AUX port in the GPU, the AUX channel will provide DDC voltage levels.
    Is the reference schematic you sent applicable with no change in this case?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 23815 points
    Hi Yaita-san,

    The last reference schematic I set you has 2k pull-ups to 3.3V(DP_PWR), this is the requirement from DP++ specification.

    Regards