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TDP158：HDMI has no output

jia jing
Prodigy 10 points
Part Number: TDP158

Tool/software:

Use TDP158

DP++ to HDMI, no output from HDMI

1、Power-on timing: VCC is faster than VDD, OE is ahead of VDD, at present, we control the timing of OE, but OE is not controlled, what is the reason for this?

2、请帮忙检查原理图

  • 0
    TI__Mastermind 30180 points

    Hi,

    1. I'm not sure what you mean by 'we control the timing of OE, but OE is not controlled'. Can you clarify what this question is asking?

    2. Can you please share the schematic in pdf format? I cannot see the net names and connections in the image you've sent. If you would like to share this privately, you can accept my friendship request and use the direct message feature on E2E:

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 10 points

    Hello

    1. TD2 does not meet the time requirements. We use MCU to control OE timing and enable OE after VDD. However, the waveform we measured was OE enabled before VDD. Can our software control the OE pin? Or is the timing of OE already specified internally in the chip, so we don't need to control it?

    2. Please help check the schematic

    14_HDMI.pdf

    Thank you

  • 0 in reply to jia jing
    TI__Guru**** 177071 points

    Hi,

    Keeping OE low until VDD and VCC becomes stable avoids any timing requirements as shown in Figure 7-3 of the TDP158 datasheet. You can use an MCU to control OE, but It is critical to transition the OE from a low level to high after the VCC/VDD supply has reached the minimum recommended operating voltage. You can also remove the MCU control of the OE pin to create a passive RESET circuit and change C197 to delay the reset timing.

    When you probe the TDP158 output such as the clock, do you see the clock and is the clock frequency correct?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 10 points

    Now the question is that I control the OE with the mcu, the OE is unresponsive and not controlled by the mcu, is there a problem with my circuit?

  • 0 in reply to jia jing
    TI__Mastermind 30180 points

    Can you show the voltage level on the VCC, VDD, and OE pins when the device is powered up? I'd like to see these measured on an an oscilloscope if possible. From the schematic, I don't see anything wrong with the OE circuit. Make sure the OE signal net from your MCU is routing to the DDI3 HDM OE# net in the schematic.

    If OE is rising correctly and you do not see any output from the TDP158, make sure that the HPD signal is connected and there is valid data at the inputs. You can see from the datasheet that HPD needs to be high and a valid clock needs to be detected before the TDP158 enables its transmitters in pin strap mode:

    In your schematic I see the connection from the HDMI receptacle to the HPD on our device has a resistor network included. Can you check that HPD is rising correctly (5V) at the TDP158 HPD pin?

    Best,

    Shane