ZHCSMR1C october 2019 – september 2021 UCC5870-Q1
PRODUCTION DATA
AI* require a series resistor and bypass capacitor (RC filter) to ensure best results. The values must be selected based on the required corner frequency for the input. A tradeoff must be made between response time, in the case of SCP and OCP monitoring, and the noise during ADC measurements. The DC input impedance of the AI* inputs is very high. However, as the signal frequency goes up, the input impedance decreases. The input impedance can be estimated as:
Where fS is the frequency of the signal. The filter The recommended RC for OCP/SCP monitoring is 100ohm and 100pF. This provides a quicker response with the drawback of more noise in the measurement. The RC chosen for the other inputs used in the application circuits is 10ohm and 10nF. All of the ADC data taken on these inputs in this datasheet are based on those RC values. For best results for ADC accuracy, it is recommended to use these components. If a different corner frequency is required, select a frequency that provides sufficient accuracy with the decreased AI* input impedance. The corner frequency is calculated using the following equation: