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TLV320ADC6140: THE ANALOG INPUT RANGE?

Miao
Prodigy 30 points
Part Number: TLV320ADC6140

Tool/software:

Hi 

I have a question about the TLV320ADC6140  analog input voltage. In the datasheet,the analog input range shows below

but when I use the analog differential input and AC-coupled to the device, for example, when I input AC (1khz@±1v VPP), is this situation suitable for this analog input range. If is Okay, do I need any other register design for this AC input?

  • 0
    TI__Expert 7730 points

    Hi,

    The above table mentions the min and max. allowed voltage to be seen on the INxP/INxM device pins. Since you have mentioned that you have AC-coupled the device, I am assuming that you are giving the +/-1V AC signal at the cap terminal (marked in green below), and not at the device pin (marked in red below). If this is the case, then the device is expected to ensure that the voltage at the INxP/INxM pins is per the above table.

    Thanks and Regards,

    Lakshmi Narasimhan

  • 0 in reply to Lakshmi Narasimhan Badrinarayanan
    Prodigy 30 points

    Hi,

    According to  your response, can I understand that there is an internal bias in the chip? Actually  I need to use  two channels with  AC coupling and another  two with DC-coupling.  the signal is ±1.4VPP, for each INxN/INxP , is it acceptable to set an external bias of 1.5V for the DC-coupled channels?

  • 0 in reply to Miao
    TI__Expert 7730 points

    Hi,

    Yes, there is an internal bias in the chip that ensures that the INxP/M pin voltages remain withing the recommended values, when operating in AC-coupled mode.

    In DC coupled mode, for the input swing mentioned, 1.5V DC bias should be good enough to ensure the same.

    Thanks and Regards,

    Lakshmi Narasimhan

  • 0 in reply to Lakshmi Narasimhan Badrinarayanan
    Prodigy 30 points

    Hi

         the input signal is shown below; however, the ADC output indicates that one channel lacks bias resulting in a DC offset in the output signal. and I test the voltage at the device pin,  the INP is 1.25V,but the INM is only 120mV.

      I am not sure whether it is ok for device, and How could it happend?

      

  • 0 in reply to Miao
    TI__Expert 7730 points

    Hi Miao,

    Basically, there is a bias on IN1P, but not on IN1M pin, is that correct?
    Can you share the schematic and register configurations done while doing this test?

    Thanks and Regards,

    Lakshmi Narasimhan