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DAC81408: About VCC supply

H264ER
Intellectual 290 points
Part Number: DAC81408

Do  VCC supply need  a LDO for a stable output ?  Can a DC-DC regulator supply VCC？

  • 0
    TI__Mastermind 28828 points

    Hello,

    An LDO would be the recommended supply for a stable output. Any switching noise from a DCDC regulator will appear on the analog outputs. 

    Best,

    Katlynne Jones 

  • 0 in reply to Katlynne Jones
    Intellectual 290 points

    Why? I think ,the switching noise will not appear on the output directly, it will be suppressed by PSRR of output amplifier. ok?

  • 0 in reply to H264ER
    TI__Guru 53183 points

    Hi,

    It depends on the PSRR of the output amplifier and the frequency of the DCDC.  Generally, our devices have limited bandwidth, so noise over ~500kHz should probably be filter externally.  We generally do not see better than -60dB PSRR, so it depends on the magnitude of the supply ripple.  If you know the switching frequency, you can use some techniques to filter just that.  You could improve noise performance by adding more discrete capacitors or series resistors on the supply pins to help attenuate the noise.

    Thanks,

    Paul