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AD5429: DAC does not start up correctly sometimes

I have a problem that AD5429 can not start up correctly. The start up fails once or twice every 10 times power up.

In that case, DAC output does not change even tough applying any command and power up command. Does not respond to program (Clear DAC output to zero scale - 0xBXXX) and hardware reset (~CLR pin to 0). DAC use both channels: 1) as a programmble gain element; 2) standart unipolar mode. If DAC start correctly, work both channels, reset and correctly responds to commands from the microprocessor. Please refer to the attached my schematic and let me know if there are anything that need an improvement.

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  • I tried both solutions:

    • VDD is applied first, followed by reference voltage on VREFB, then lastly Vin on RFBA;
    • start from no power applied to DAC, just supply VDD then VREFB.

    DAC starts incorrectly sometimes.

     

    In case of incorrect start the outputs of the DAC has one of three values: zero-scale, midscale and full-scale.

     

    If only one DAC is connected, the problem persists.

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  • I tried both solutions:

    • VDD is applied first, followed by reference voltage on VREFB, then lastly Vin on RFBA;
    • start from no power applied to DAC, just supply VDD then VREFB.

    DAC starts incorrectly sometimes.

     

    In case of incorrect start the outputs of the DAC has one of three values: zero-scale, midscale and full-scale.

     

    If only one DAC is connected, the problem persists.

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