SBAS813 June 2018 ADS8688AT
PRODUCTION DATA.
Each analog input channel in the device presents a constant resistive impedance of 1 MΩ. The input impedance is independent of either the ADC sampling frequency, the input signal frequency, or range. 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_nP input pin with an equivalent resistance on the AIN_nGND pin is recommended. This matching helps to cancel any additional offset error contributed by the external resistance.