Each analog input channel in the device presents a constant resistive impedance of 1 MΩ. The input impedance for each channel is independent of either the input signal frequency, the configured range of the ADC, or the oversampling mode. 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 (see Figure 7-3). This matching helps cancel any additional offset error contributed by the external resistance.