18.4.2.3 CIC Filter

The CIC filter is responsible for demodulation. Its input is provided either through the CICxDIN register or directly from ADC channels, depending on the mode of operation. The filtered output is available in the CICxDOUT registers and can be further processed using a software tracking loop or an arctangent function to determine the resolver angle. For tracking loop implementations, an error signal is required as input; this signal can optionally be computed in hardware using the CORDIC block.

The CIC filter operates in 4 stages as shown in Figure 18-9:
  1. Input sample validity check
  2. Heterodyne (synchronous demodulation)
  3. Filter
  4. Auto-shift
Figure 18-9. CIC Channel Block Diagram