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ADS7816: Input stage protection

Expert 3745 points
Part Number: ADS7816

Dear e2e support,

Can we give more information on the internal input stage or our ADS7816?

Do we have any diode protection at the +In and -In pin?

If yes, is there a max current qualified for these diodes?

Regards,

  • Hello TISL,

    Welcome to E2E forum.

    ADS7816 is a typical switched-capacitor input structure SAR ADC, the simplified circuit schematic can be referred to the Precision Labs ADCs on-line training, the sampling capacitor on ADS7816 is 25pF which is specified in 2nd page and described in 8th page of datasheet.

    Since ADS7816 is a very mature device, I do not have detailed information about internal structure on hand, but even if there are protection diodes on the input inside the ADC, we still strongly recommend to design a external protection circuitry as a secondary protection to protect the ADC against any potential external over-voltage transient, because we never want to turn on internal protection diodes.

    Generally the ADC requires the input current less than +/-10mA, but the current less than +/-1mA is recommended with some margins.

    Below is an external protection circuity recommendation for protecting this ADC, since the absolute maximum rating for analog input on ADS7816 is -0.3V to (+Vcc+0.3V), so a schottky diode with smaller forward voltage and capacitance is a good solution, Rp should be selected properly to limit the current and help to clamp the signal, and Rflt is designed to limit the current to ADC input.

    Hopefully this is helpful to you. Thanks.

    Best regards

    Dale