47.6.9.6 Interpolation Mode

The DAC provides interpolation that allows for oversampling ratios (OSR) of 2x, 4x, 8x, 16x or 32x. Interpolation mode is selected by writing a non-zero value to the Oversampling Ratio bits in the DACx Control register (DACCTRLx.OSR).

The data is sampled once over OSR trigger events and then recomputed at the trigger sample rate using a third-order SINC filter.

The figures below show the spectral mask of the SINC filter depending on the selected OSR. $f_s$ is the sampling frequency of the input signal which corresponds to the trigger frequency divided by OSR.

The Filter usage bit DACCTRLx.FEXT determines whether the filter is integrated to the corresponding DAC or used as a standalone filter driven by DMA. If DACCTRLx.FEXT=0, the DAC takes the filter output while the value of RESULTx is reading zero. Conversely, If DACCTRLx.FEXT=1, the DAC value remains zero, and the value of RESULTx register reflects the filter output.