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ADS8344EB input impedanse

Tomohiro Nagasawa
Expert 1710 points
Other Parts Discussed in Thread: ADS8344

Dear Support team

My customer has trouble with an accuracy of the AD conversion.

Could you privide input impidanse of each pin?(especially CH0～CH7 analog input)

APL: Automotive invertor R＆D

Regards

Tomohiro Nagasawa

  • 0
    TI__Genius 9975 points

    Hello Tomohiro Nagasawa-san,

    The amplifier driving the ADS8344 inputs needs to charge the 25 pF input capacitor of the ADC and settle to less than ½ LSB within the sampling time.

    Hope this helps.

    Best regards,

    Jose

  • 0 in reply to Jose Duenas
    Expert 1710 points

    Jose-san

    Thank you for quick response.
    Customer says that variability of A/D conversion accuracy between each ch is large.
    Could you provide variability of input impedance? (Lough data is helpful for us)

    Regards
    Tomohiro Nagasawa

  • 0 in reply to Tomohiro Nagasawa
    TI__Genius 9975 points

    Hello Tomohiro Nagasawa-san,

    The multiplexer connects each input to the very same 25 pF input capacitor so there is no variability between channels for a single unit.

    Could you please send a schematic of the signal sources, amplifiers and ADC connections your customer is using to drive the ADC? What are the signal characteristics (amplitude, frequency)?

    Are they using internal or external clock for the conversions? What frequency?

    Could you please include also the schematic of the voltage reference and buffer used?

    Could you please send some on their results? What input signal they put into each channel and what codes did they get out?

    It is possible that their driving circuitry is no settling properly.

    Best regards,

    Jose