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debugging broken TVOUT on DM365

Clyde Hinkle
Prodigy 20 points

We have a custom board design using a DM365 and we've built ~10-15 units. On two of the boards, the DM365's TVOUT is no longer driving a video signal out. After probing i've also noticed on both boards that the IREF pin (pulled down with 2.4k) is at ~0V and the VREF pin (using the same 0.5V bias source circuit as the EVM from Spectrum Digital) is also at ~0V. With the board powered off and using an ohmmeter, i don't see any shorted connections to ground on any of these pins.

Questions:

  1. What should the IREF pin look like when operating? When DACs are disabled?
  2. Any mode or other board problem where the VREF pin becomes a grounded output or has a much higher input bias current?
  3. Any suggestions on register settings or other board level signals to look at before assuming the video outputs are just damaged?

Regards,

CW

  • 0
    Expert 1150 points

    CW,

    Your problem sounds like hardware.

    Have you checked that the DM365 receives the analog 1V2 and 1V8?

    Have you checked the continuity between the analog ground and the digital ground?

    Have you checked that the VREF receives the 3V3.

    Hope this helps.

    Rgds

    KB