SBASAD2 November 2021 ADS130B04-Q1
The accuracy of the analog supply directly impacts the measurement accuracy of the PTC in this measurement implementation. In order to increase the temperature measurement accuracy, channel 0 of ADS130B04-Q1 is used to measure the analog supply. The measured AVDD value is then used in Equation 11 to calculate RPTC.
A resistor divider (R1 and R2) is used to attenuate the 3.3-V analog supply voltage down to less than 1.2 V so that channel 0 can measure the voltage using gain = 1 with AIN0N connected to AGND. The resistor divider needs to be chosen so that the voltage on AIN0P stays below 1.2 V at the maximum AVDD voltage that can occur in the application. Following Equation 12, the resistors are chosen as R1 = 20 kΩ and R2 = 10 kΩ to allow measurements up to AVDD = 3.6 V.
The analog supply voltage is calculated using Equation 13: