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PGA280 offset voltabe

mehmet ekici
Intellectual 430 points
Other Parts Discussed in Thread: ADS1292, PGA280

Hello,

We designing a custom board with PGA280 and ADS1292. We measure about +20 to - 30mV of offset voltage at the output of the PGA280. Would you please help us to resolve the issue ?

What can cause such a very low offset device to produce this much of error ?

I have enclosed the schema of the circuit.

Regards,
Mehmet

Sheet1.pdf
  • 0
    TI__Mastermind 27715 points

    Hello Mehmet,

    The first thing I would check is if the input current buffer (BUF) is enabled. If so, the typical offset voltage jumps to 15mV, as stated on p.4 of the PGA280 datasheet.

    Which gain settings are you using in your circuit? The offset voltage of the PGA280 increases with decreasing gain, as shown below. The worst case is about 1.7mV at G = 0.125V/V.

    The offset voltage spec for the PGA280 is valid with G=1V/V, VSP = +15V, VSN = -15V, VCM = 0V, BUF inactive, and a load resistance at each output to VOCM = VSOP/2. You have a very different power supply scheme, since you have a single-ended supply on the input side (VSP and VSN). Have you tried the following:

    • Disabling BUF option
    • Adjusting the input common-mode voltage to +12V ((VSP+VSN)/2)
    • Placing 2.5k load resistors from VOP and VON to VOCM

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps