SBAS633E February 2016 – August 2022 ADS8681 , ADS8685 , ADS8689
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
The device presents a resistive input impedance ≥ 1 MΩ on each of the analog inputs. The input impedance is independent of the ADC sampling frequency or the input signal frequency. The primary advantage of such high-impedance inputs is the ease of driving the ADC inputs without requiring driving amplifiers with low output impedance. Bipolar, high-voltage power supplies are not required in the system because this ADC does not require any high-voltage, front-end drivers. In most applications, the signal sources or sensor outputs can be directly connected to the ADC input, thus significantly simplifying the design of the signal chain.
In order to maintain the dc accuracy of the system, matching the external source impedance on the AIN_P input pin with an equivalent resistance on the AIN_GND pin is recommended. This matching helps cancel any additional offset error contributed by the external resistance.