SBASB13 December 2024 AMC0311S
PRODUCTION DATA
Place a RC filter in front of the device to improve signal-to-noise performance of the signal path. Input noise with a frequency close to the ΔΣ modulator sampling frequency (typically 10MHz) is folded back into the low-frequency range by the modulator. The purpose of the RC filter is to attenuate high-frequency noise below the desired noise level of the measurement. In practice, a cutoff frequency that is two orders of magnitude lower than the modulator frequency yields good results.
Most voltage-sensing applications use high-impedance resistive dividers in front of the isolated modulator to scale down the input voltage. In this case, a single capacitor, as shown in Figure 8-2, is sufficient to filter the input signal. For (R1 + R2) >> RSNS, the cut-off frequency of the input filter is 1 / (2 x π x RSNS x C5). For example, RSNS =10kΩ and C5 = 100pF results in a cutoff frequency of 160kHz.