31.4.6 Low-Pass Filter Mode

The Low-Pass Filter mode (MD = ‘b100) acts similarly to the Average mode in how it handles samples; it accumulates samples until the CNT value is greater than or equal to RPT, then triggers a threshold comparison. But, instead of a simple average, it performs a low-pass filter operation on all of the samples, reducing the effect of high-frequency noise on the total, then performs a threshold comparison on the results. In this mode, the CRS bits determine the cutoff frequency of the low-pass filter (as demonstrated by Digital Filter/Average). Refer to the Computation Operation section for a more detailed description of the mathematical operation.

For more information about Low-Pass Filter mode, refer to the following Microchip application note, available in the corporate website (www.microchip.com):

• AN2749, “PIC18 12-bit ADCC in Low-Pass Filter Mode”