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About Application Report:SBAA180

Chang Yu Cheng
Prodigy 10 points
Other Parts Discussed in Thread: ADS1248, ADS1247

In SBAA180 document(example temperature measurement applications using the ADS1247 and ADS1248),

page 6, second content,

Why is the maximum differential input to the modulator is equal to [(AVDD-AVSS)/2]  ???

  • 0
    TI__Guru** 113765 points

    Chang Yu Cheng,

    Welcome to the forum!  2.5V is the desired reference voltage created with 3mA going through the Rbias resistor (833.3 ohms).  This reference voltage value is the maximum allowable +/- swing for AVDD-AVSS=5V.  This is also assuming a PGA gain of 1.

    Later in the text the example refers to PGA=128, which will reduce the input range to +/-19.5mV.

    Best regards,

    Bob B