This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN65DP149: SN65DP149 DP to DVI Converter Functional Problem

Part Number: SN65DP149


I am working on a DP to DVI converter using SN65DP149 IC. Manufactured the PCB, assembled but it is not functioning.

I am using pin strapping for configuring the converter as follows:

I2C_EN/PIN is low, pin strap mode

EQ_SEL/A0 pin is floating. adaptive EQ

SLEW_CTL pin is high, fastest data rate

PRE_SEL pin is floating, 0dB

HDMI_SEL/A1 pin is high, configured for DVI

DP connector is about 5 cm from IC (on flex part of the converter), DVI connector is over a 40cm cable. Differential pairs are twisted.

When measured pins, OE pin is about 2.5V. When connected to the source and monitor, HPD_SNK pin is 5V, HPD_SRC is 3.3V, I2C pins are pulled up.

Attaching schematic of my board:

  • Hi Eray,

    DP149 is a passive converter or level shifter from DP++ to HDMI/DVI. This is not an active converter from DP to HDMI/DVI.

    The passive converter takes HDMI/DVI video AC-coupled(This is DP++) at the input and sends HDMI/DVI video DC-coupled at the output.

    To tell the GPU to send HDMI/DVI video you need to assert CAD(CONFIG1) signal, currently, you have it tied to GND.

    Long story short

    Make sure GPU is DP++ capable

    On DP connector assert CONFIG1(CAD) high

    Finally is better to use snoop mode on SCL_SNK/SDA_SNK, in case GPU or displays don't support I2C clock stretching, I will send you reference design by email.


  • Dear Garcia,

    Thanks for your reply.

    My final setup will be a DP++ output, but currently trying my converter on an 'Nvidia Quadro K620' graphics card, which I am not sure if DP or DP++. Datasheet of this graphic card says DP 1.2 output, but nothing about DP++. Should I assume this is a non-DP++ ?

    I have noticed CONFIG1 (CAD) lately and added a 100K pull-up to 3.3V supply pin of DP connector. When plugged, I measure 800mV on this pin. Couldn't find a minimum level for this pin. Is 800mV OK? Should I use a lower resistor, or directly tie?

    About snoop mode, I don't know what it is yet, but will look and try it.

    Thanks and Regards.
  • Hi Eray,

    I'm not familiar with this video card, computers DP++ capable have the dual mode symbol printed, however having 800mV is very low in CAD after asserting it high, which makes me think it doesn't support DP++.

    Tying CAD to 3.3V is not recommneded, in some old GPU CONFIG1 is tied to GND, so this woule make a short circuit.
    Check if the current provided by the computer through DP_POWER is enugh to power DP149.

  • Seems logical, I think this video adapter is not DP++. There is another PC with DP++ output, I will try on that and share the results. Thanks again!
  • Hi Moises,

    I have tried my board with a DP++ dual-mode source, not working yet. And also, I have observed that Pin 13 of DP connector, which is Cable Adapter Detect, is again around 800mV levels.

    So, I have checked with 'VESA DisplayPort Interoperability Guideline v1.1' and part 5.4 states following:

    I am confused about this, are we pulling high, if so, why is it expecting a voltage under V_IL?


  • Hi Eray,

    Document 'VESA DisplayPort Interoperability Guideline v1.1' is the one available on the internet, but in 2009 version 1.1a was released where that "typo" was corrected. In document version 1.1 figure 5-1 you can see there is 1M pull-down on pin 13, and a 100k pull-up on the same pin of adaptor's side.

    Perhaps the GPU is not sensing CAD(Marked as optional in DP++ standard) and is looking for cable adaptor registers, could you configure DP149 for HDMI instead of DVI?

    Could you monitor activity on AUX channel?