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Query regarding use of DAC 7760

SS_hwdesign
Prodigy 250 points

Other Parts Discussed in Thread: DAC7760

Hi..

We are using DAC 7760 in one of our design.

We have designed 2 separate Power Supplies for +15 V & -15 V which are derived from +24 V external supply.

These are operating properly and giving Output as +15.30 and -15.71 respectively.

Now, as soon as we start Input Power Supply (+24 V), +15.30  remains stable, but -15V supply start degrading very fast and it continues till -9V.

Is it possible that DAC could sink the current though DVDD supply (+5V) is not given.

There are no other components / circuit connected to +/- 15 V supplies.

  • 0
    TI__Mastermind 46290 points

    Saurabh,

    Can you provide a complete schematic for this design? That will help me come up to speed on your design quickly.

  • 0 in reply to Kevin Duke
    Prodigy 250 points

    Kevin,

    Sorry, but I can not provide you complete schematic.

    Here I am sharing how we have done connections to DAC7760 in our circuit.

  • 0 in reply to SS_hwdesign
    TI__Mastermind 46290 points

    Saurabh,

    Your schematic around the DAC7760 looks fine to me, in fact it's similar to a number of the designs I've done with the device.

    I would find it very unlikely that a floating DVDD terminal is the cause of this behavior. The negative supply is only used by the output amplifiers for the voltage output stage - so there isn't any real path for the negative rail to interact with DVDD. Do you see this behavior with the voltage output enabled or does this happen immediately on power up? By default the voltage and current output stages are disabled so the negative supply rail shouldn't be doing anything at all.

    Have you tested this with and without the DVDD rail and seen different behavior? This would be the first time I've heard of such a thing...

  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points

    Saurabh,

    Any update on this issue?

    The thermal pad connection isn't shown on your schematic. What net is the thermal pad connected to?

    Can you describe your power-supply sequence?

  • 0 in reply to Kevin Duke
    Prodigy 250 points

    Sorry Kevin, for no further updates from my side.

    Problem resolved.
    It was our mistake. We have connected Thermal Pads to GND instead of AVSS

    Thanks a lot for helping us...!

    Saurabh