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PGA281 power sequence

rungsimant sitdhikorn
Prodigy 50 points

Other Parts Discussed in Thread: PGA281

Hello

   I need your suggestion on power supply sequence on page 21 Figure 45, DVDD on first, then delay time with RC on VSOP and final 2-times delay time on VSP,VSN.

  On page 20, However, "DVDD must be 1 V less than VSP". DVDD can be turned on without the analog supply being present and is operational."

 Is it necessary to connect a diode between DVDD and VSP for clamping voltage?

thank you

  • 0
    TI__Mastermind 27715 points

    Hello Rungsimant,

    Your proposed power supply sequence would work. Please ensure that no analog input voltage is applied to the PGA281 before VSP and VSN are on in order to avoid violating the absolute maximum ratings of the device.

    DVDD must be at least 1V less than VSP, but is usually several volts less as VSP is the high-voltage analog input stage supply and DVDD is a standard digital logic-level supply. I do not recommend using a diode's voltage drop to create DVDD from VSP. Rather, use another power supply entirely.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

  • 0 in reply to Ian Williams
    Prodigy 50 points

    Hello.

      thank you for your comment. I try to make sure there is no conflict on power supply sequence on PGA281.

      Even If there is no analog i/p.  Yes, DVDD is "usually" less than VSP.

      But if i supply DVDD and VSP on the same time,  From Figure 45 DVDD rise first and then VSP increase with 10.34us delay time.

      This violates "DVDD must be at least 1V less than VSP" and how about the IC?

      Is it necessary using power supply sequencer?

    thank you

  • 0 in reply to rungsimant sitdhikorn
    TI__Mastermind 27715 points

    Hello Rungsimant,

    The condition that DVDD must be at least 1V less than VSP applies once the power supply rails have fully turned on and stabilized. The microseconds during power on where DVDD comes up quicker than VSP is not a problem.

    Best regards,

    Ian Williams