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ADC31JB68: Protection to the ADC input

Danilo A.
Mastermind 28660 points
Part Number: ADC31JB68

Hi Team,

We have received this inquiry from our customer,

I have an analog signal with wider dynamic range than the ADC can handle, so the signal could regularly exceed the ADC's analog input range.  These excursions will typically be brief, probably lasting for 100 ns to a few us.  My original signal is single-ended, and I plan to drive the differential ADC inputs using a fully differential amplifier to perform the single-ended to differential conversion.  The difference between the largest ADC code and the ADC absolute maximum is only 0.3V.  How can I protect the ADC inputs and still maintain the full dynamic range and analog performance?

I found the E2E FAQ below but not sure if it can still maintain the full dynamic range and analog performance of the ADC.

e2e.ti.com/.../faq-does-ti-have-any-information-on-protection-circuits-for-electrical-overstress-eos-for-adcs

Regards,

Danilo

  • 0
    TI__Genius 12780 points

    Hi Danilo,

    Given that the signal chain amplitude is larger than that of the ADC full scale range, it sounds like there are two options to resolve this issue.

    1) Reduce the gain of the FDA to ensure that the excursions do not exceed the ADC full scale range (would give up some of the average dynamic range).

    2) Add diodes in the signal chain (before input to FDA, after output of FDA) to clamp the signal to avoid overdriving the ADC (recommended).

    It looks like there are some good articles in the link that you shared to get started on using diodes in the signal chain. One thing to consider is that the diode will have some parasitic capacitance that should be accounted for when considering the frequency response or designing the AAF/LPF for the signal chain.

    Best Regards,

    Dan