ZHCSJC0 January 2019 ADS1260-Q1 , ADS1261-Q1
ADVANCE INFORMATION for pre-production products; subject to change without notice.
In PGA mode, the input voltage must be within the specified input range for linear operation. The following exercise shows how to use Equation 5 to verify the input voltage is within specification. The exercise is a thermocouple with the negative lead connected to AINCOM and the level-shift voltage enabled (2.5 V). The gain factor = 32 and the ADC is powered by a single 5-V power supply. The summary of conditions are:
Evaluation of the equation results in:
1.23 V < 2.5 V and 2.56 V < 3.52 V
The inequality is satisfied, therefore the absolute input voltages are within the specified PGA input range. The input requirement can also be verified by measuring the PGA output voltages (pins CAPP and CAPN) with a voltmeter. Check that both outputs are within the range: AVSS + 0.3 V < V(CAPP) and V(CAPN) < AVDD – 0.3 V, under the worst-case input and power-supply conditions.