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ADS8668: Reverse connection input

ttd
Mastermind 9395 points

Part Number: ADS8668
Other Parts Discussed in Thread: ADS8688

Dear Technical Support Team,

My input circuit of ADS8668 is below.

Signal generator that I have makes only 0～10V. it can't make 0～-10V

So I try to input  reverse connection input(AIN_0P=0V and AIN_0N=0～ - 10V), then ADS8668 looks converting correctly(0～-10V).

I understand that ADS8688 supports only single-end input.

This is PGA on datasheet. I'd like to calculate above behavior on PGA circuite.

However I don't know the PGA behavior and RDC and RFD when input range setting is ±10V.

Best Regards,

ttd

  • 0
    TI__Guru 50025 points

    Hi ttd,

    The AIN_nGND should be connected to the AGND and the voltage should be limited to  -0.1V~0.1V for proper operation, what you did is not recommended and you will not be able to achieve the performance specified in the data sheet and also may damage the device. 

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Mastermind 9395 points

    Hi Dale Li,

    Thank you for your reply. I understand.

    By the way, could you show the  PGA behavior and RDC  value and RFD value when input range setting is ±10V?

    Of course,  AIN_nGND is connected to the AGND and input to the AIN_p

    If you show

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Guru 50025 points

    Hi ttd,

    I do not have the details about internal circuity of the device including a model, however the internal PGA is properly configured according to the bit setting in the Range Select Registers. In order to use this ADC and achieve the performance specified in the data sheet, the guidance and recommendations in the data sheet should be followed.

    Thanks&regards,

    Dale