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TDP1204: TDP1204/TMDS1204 Not Responding on I2C

Marco Groeneveld
Prodigy 10 points
Part Number: TDP1204
Other Parts Discussed in Thread: TMDS1204

Tool/software:

Hi everyone,

We've developed an HDMI 2.1 FPGA development board using the TDP1204 and TMDS1204 devices. On approximately half of the boards, the device does not respond to I2C communication.

Here are the configuration details:

  • MODE pin: Floating (I2C mode)

  • VCC: 3.3V

  • VIO: 1.8V

  • I2C lines (SCL/SDA): 1.5kΩ pull-up resistors to VCC

  • EN pin: 1kΩ pull-up to VIO and a 100nF decoupling capacitor

We've tried accessing all supported I2C addresses (0x5B, 0x5C, 0x5D, 0x5E), but the device doesn't acknowledge any of them.

I’ve attached a scope capture of the I2C communication. The I2C interface runs at 100 kHz.

Additional observations:

  • The HPD_OUT pin is high.

  • When I force the EN pin low, HPD_OUT goes low.

  • Releasing EN (allowing it to be pulled high to VIO) causes HPD_OUT to go high again.

Does anyone know why the device might not be responding to I2C? 

Any insight or suggestions would be greatly appreciated.

Thanks!

Marco

======

  • 0
    TI__Genius 12716 points

    Hi Marco, 

    I2C needs to be connected to VIO not VCC. Since your VIO and VCC are different, have you tried connecting I2C bus to VIO and do read/writes?

    Please let me know. 

    Best,
    J

  • 0 in reply to J
    Prodigy 10 points

    Hello J,

    Thanks for your feedback. I haven't connected the I2C to VIO yet. At this moment that's not an easy task. 
    However the TDP1206 datasheet section 6.5 - Electrical Characteristics mentions a high level voltage input (Vin_1p8v) for SCL / SDA from 1.19V till 3.6V for test condition VIO = 1.7V and VCC = 3.6V.  This would suggest that this configuration is supported. 

    Best Regards,

    Marco

  • 0 in reply to Marco Groeneveld
    TI__Genius 12716 points

    Hi Marco, 

    I understand but it may cause an issue. 
    If changing to 1P8V is hard, could you try ABA swapping the device and see if the issue follows the board or the chip?
    Please let me know. 

    Best,
    J

  • 0 in reply to J
    Prodigy 10 points

    Hello J,

    I’ve rewired the I2C lines to use VIO (1.8V), but unfortunately, this didn’t resolve the issue. The device still doesn’t respond to any I2C addresses.

    I also measured the power supply ramp-up sequence and the EN pin. Everything appears to be compliant with the Power-On Timing Requirements (Figure 7.1).

    The HDMI device is mounted on an FMC card. I tested the same (failing) FMC card on a different FMC carrier board, and in that setup, the HDMI device does respond to I2C.

    While comparing the power-on timing between the two carrier boards, I observed that:

    • On the working board, Vcc ramps up faster than VIO.

    • On the failing board, VIO ramps up earlier than Vcc.

    I've attached the scope captures showing the power-on sequence.

    Could the earlier rise of Vio lead to latch-up or undefined behavior? The datasheet doesn't mention any power sequence recommendation. 

    I don’t have control over the individual power supply ramp sequences.

    Best regards,

    Marco

  • 0 in reply to Marco Groeneveld
    TI__Genius 12716 points

    Hi Marco, 

    Power up sequence should not matter as long as the RESET_N is low until both powers are ramped up. I will verify this on the EVM and get back to you. In the meantime, it is weird that the same carrier boards have two different power up sequence. Have you tried ABA swap to see if the issue follows the device, or the board?

    Best,
    J

  • 0 in reply to J
    TI__Genius 12716 points

    Hi Marco, 

    I have tried ramping VIO before VCC and I could still access I2C without any problem on the EVM. Please let me know if you could do ABA swap to see if this issue follows the device, or the board. 

    Best,
    J