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ADS8588S: AIN_nP float input

ThomasZhong
Prodigy 30 points
Part Number: ADS8588S

Hello Sir:

1. According the analog inputs diagram.I am still confused when the device config AIN_nGND tie to the GND, AIN_nP float, range is select +/-5V, how to calculate the output is 2V? Can you show more detail?

2. Why we should consider the input leakage current. according above config the leakage current is -7uA to 3uA. when AIN_nP float how much the leakage current?

  • 0
    TI__Mastermind 45715 points

    Hi Thomas,

    The 2V bias is needed and created by ADS8588S' internal AFE circuit, when your ADC's input is floating without pull-down resistor, the conversion code of this 2V will be seen on ADC's digital output. When your analog signal is connected and available on ADC's analog input pin, this internal 2V bias voltage can not be seen on ADC's conversion code, which means that the 2V bias voltage does not have any impact to your analog signal and conversion code.

    The input leakage current is a standard specification shown in the datasheet, the datasheet shows all information about the ADC. This leakage current is really small and you may not need to pay attention to this parameter if your front-end circuit does not have a very large resistance. When the ADC's input is floating, there is no leakage current on the input.

    Regards

    Dale