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ADS8638: HVSS and HVDD lines voltage

Danny Andreev
Intellectual 310 points
Part Number: ADS8638

Hey,

I am designing a circuit that will read in a voltage of between 1 and -1v and send it over spi. I have chosen the ADS8638 chip because I need to read in 8 voltages at a high rate.

My question is about weather I am using the HVSS and HVDD lines correctly (applying -5, 5v respectively). I cant find how stable I need these input voltages to be.

Also this is my first iteration of this circuit and Id like to get it right. Do you guys see any flaws in the layout?

Thanks!

-Danny

P.S.

Another question about voltage measurements of line voltage. Should I measure the hot like with respect to ground (earth) or the neutral line. If earth ground, then is it possible to reference with respect to the earth signal on this chip?

  • 0
    TI__Mastermind 24970 points
    Hello Danny,

    From your schematic, both HVDD abd HVSS seems to be fine.
    I am assuming you will be using the +/- 2.5V range. You are losing quite a bit of resolution if your input range is only from +/-1V
    Looking at your schematic. Be sure to connect the termal pad of the device to ground.
    When making measurements be sure to use the ground the device is connected to. For the ADS8638, youwould measure using GND and not IGND

    Regards
    Cynthia
  • 0 in reply to Cynthia
    Intellectual 310 points

    Cynthia,

    I appreciate you getting back to me.

    I am using the +/- 2.5V range, and I will look into boosting the incoming signal. 
    Im glad you caught the thermal pad grounding!

    Best,

    -Danny