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DM365 - VPBE: short circuit detection of TVOUT pin?

AnBer
Mastermind 30110 points
Other Parts Discussed in Thread: OPA361

Team,

Could you please confirm the following?

There are some support for short circuit detection on the DM365 TVOUT pin of the DAC. So looking at the description provide in SPRUFG9A it looks like that you can detect the short circuit via VDAC_CONFIG.TVSHORT and VDAC_CONFIG.PDTVSHORTZ bit fields.
Looking at DM365 datasheet SPRS457B page 149 a video buffer can be enabled via some registers bit field.

Is it expected that this video buffer can act as protection circuit in case of short circuit on the TVOUT? If yes can the TVOUT be permanently shorten without damaging the device?
If it is suppose to protect for a short period of time do you have some timing information about it?

Thanks and BR,

A.

  • 0
    Expert 2315 points

    Was there any resolution to this as I want to use a EVM board in a system and at least protect the outputs against shorts and maybe another video output being plugged into the output erroneously?

    Thanks, Jinh T.

  • 0 in reply to Jinh
    TI__Mastermind 30110 points

    According to the last feedback I got regarding Stand Definition (SD) video DAC and internal amplifier:

    a) Internal amplifier:
    - The internal video OPA does support nor short circuit protectection neither short circuit detection.
    - The short circuit detection has not been validated. The VDAC_CONFIG.TVSHORT and VDAC_CONFIG.PDTVSHORTZ bit fields will be removed in the next release of the VPBE user's guide - SPRUFG9.

    b) For using an external amplifier:
    - The internal amplifier can be bypassed.
    - You could use an OPA361 as an external buffer (with integrated filter), which supports continuous short condition.
    - The amplification ratio needed for SD video Composite on the DAC is as well 5.6 V/V
    - with the OPA361, we would recommend boosting the gain to 5.6V/V by decreasing the 75-ohm serial termination resistor.  We would not recommend adding an external resistor in parallel with the internal OPA361 500ohm resistor.  The internal 500ohm resistor has a 10% variance which is cancelled out by the 10% variance in the internal 4K resistor (they track each other across process and are guaranteed to match within 2%).  Adding an external resistor in parallel will compromise the matching.