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ADC3662: ADC input protection

Simon Binder
Prodigy 50 points
Part Number: ADC3662
Other Parts Discussed in Thread: , THS4541

Tool/software:

Hi,

I'm using the ADC3662 with the THS4541 as FDA like at ADC3662EVM.

In the datasheet of the ADC3662 it's mentioned that protection diodes may be needed to protect the ADC from over-voltage. There are no such diodes at the ADC3662EVM and in chapter 8.3.1 Analog Input are diodes sketched in. So my question is, above which voltage level at xINP/M should I protect the ADC? And below which voltage level are the internal diodes sufficient?

Thanks for help!

  • +1
    TI__Mastermind 27860 points

    Hi Simon,

    Please ensure the max input voltage on either of the analog input pins does not exceed the abs max ratings within the datasheet.

    Otherwise damage will occur to the ADC's internal sampling network.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Prodigy 50 points

    Hi Rob,

    As AVDD is supplied with 1.8 V, the analogue input pins AINP/M and BINP/M should not have voltages higher than 2.1 V. Is this correct? So would you suggest using TVS diodes directly on the analogue input pins or is it better to connect them to the input pin of the FDA? I have designed the FDA network like the ADC3662EVM, with the slight change that I use the positive input of the FDA instead of the negative.

    Best regards

  • +1 in reply to Simon Binder
    TI__Mastermind 27860 points

    Hi Simon,

    Yes, please ensure the analog input signals do not go above the abs max, so in this case the signal cannot be greater than +2.1V or lesser than -0.3V.

    Yes, you can use diodes on the analog inputs directly. Many people do this, however, if your application is collecting frequency domain data, then some diodes will cause distortion to the signal, particularly as the signal approaches fullscale.

    Regards,

    Rob