ZHCSIU4A September 2018 – August 2019 ADS1284
PRODUCTION DATA.
The modulator samples the buffered input voltage through an internal capacitor to perform the ADC conversion. The charging of the input sampling capacitor draws a transient current from the PGA output. Use the average value of the current to calculate an effective input impedance, as shown in Equation 5:
where
The resulting modulator input impedance is 55 kΩ (110 kΩ low-power mode). The modulator input impedance and the PGA output resistors result in systematic gain errors. The modulator sampling capacitor and PGA output resistors can each vary up to ±20% over production lots, affecting the nominal gain error.