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ADS1262: Analog input Range

Scott Morgan
Prodigy 10 points
Part Number: ADS1262

Hello, I am a little confused as to the actual input range of the ADS1262. This is my interpretation of the data sheet of the ADS1262:

If I am using the internal Vref of +2.5V, my AVDD is +5V and my AVSS is 0V, then my input range is 0V to +2.5V.  Is this correct?

If I am using an external Vref of +5V my AVDD is +5V and my AVSS is 0V, then my input range is 0V to +5V.  Is this correct?

If I am using an external Vref of +5V my AVDD is +2.5V and my AVSS is -2.5V, then my input range is -2.5V to +2.5V.  Is this correct?

Thank you very much for your time.

  • 0
    TI__Mastermind 44550 points

    Hi Scott,

    Welcome to the TI E2E Forums!

    The ADS1262's input range can be described in two different ways:

    1. The absolute input voltage range. In general, ALL input voltages must be less than AVDD and greater than AVSS. The ADC cannot measure voltages outside of the supply range, and if the input voltage really exceeds this requirement it can damage the device.

    2. The differential input voltage range. The ADS1262 always measures inputs signals differentially (with respect to some other signal), and then compares this (differential) voltage to the reference voltage. Therefore, the differential input voltage must not exceed +/- Vref / PGA (or +/- Vref after getting gained up by the PGA); otherwise, the ADC's output code will clip to the maximum or minimum code.

     

    In summary...

    • the supply voltages will set the bounds on the absolute input voltage range (for both the positive and negative inputs, no matter which input you designate as the positive or negative input).

    • the reference voltage (and PGA gain) will limit the maximum differential voltage that you can measure between input pins.

     

    FYI: Here is an Excel Calculator Tool for the ADS1262 that can tell you whether or not the ADC's input signal is out-of-range:   

    I hope that helps!

    Best Regards,
    Chris