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ADS8557: HV to +/-5V

Marina Iriarte40
Prodigy 210 points

Part Number: ADS8557

Tool/software:

Hello, 

We are analyzing possible error states of our design. We are using ADS8557 ADC in HW mode, with internal reference and Range +/-4*VREF.

Normally we have a +/-12V HV voltage; but in one possible error situation, the HV voltage can decrease to +/-5V.

Here is the question: what behaviour can we expect if HV=+/-5V? Which would be the internal reference? It would still be 2,5V?  I guess the input range wouldn't be +/-10V, would it saturate all inputs to +/-5V?

If we have an input below +5V, can we expect a correct measurement output? 

Thanks,

Marina

  • 0
    TI__Genius 10797 points

    Hi Marina,

    Thanks for your post. Let me confirm on this and get back to you tomorrow.

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    TI__Genius 10797 points

    Hi Marina,

    Thanks for your patience. If HVDD reduces to +/-5V, this will reduce the range of ADC input voltage and may affect the linearity at higher voltages. If the input voltage violates the limits highlighted below, we recommend limiting the input current to 10mA to avoid damage to the device.

    But yes, if you are using HVDD = +/-5V, you may use an input of +/-5V (ie +/-2*VREF).

    I hope this helps.

    Best regards,

    Samiha