DocID024597 Rev 5 719/1830
RM0351 Digital filter for sigma delta modulators (DFSDM)
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Figure 170. Example: Sinc
3
filter response
For more information about Sinc filter type properties and usage, it is recommended to study
the theory about digital filters (more resources can be downloaded from internet).
24.4.9 Integrator unit
The integrator performs additional decimation and a resolution increase of data coming from
the digital filter. The integrator simply performs the sum of data from a digital filter for a given
number of data samples from a filter.
The integrator oversampling ratio parameter defines how many data counts will be summed
to one data output from the integrator. IOSR can be set in the range 1-256 (see IOSR[7:0]
bits description in DFSDM_FLTxFCR register).
Table 156. Filter maximum output resolution (peak data values from filter output)
for some FOSR values
FOSR Sinc
1
Sinc
2
FastSinc Sinc
3
Sinc
4
Sinc
5
x +/- x +/- x
2
+/- 2x
2
+/- x
3
+/- x
4
+/- x
5
4 +/- 4 +/- 16 +/- 32 +/- 64 +/- 256 +/- 1024
8 +/- 8 +/- 64 +/- 128 +/- 512 +/- 4096 -
32 +/- 32 +/- 1024 +/- 2048 +/- 32768 +/- 1048576 +/- 33554432
64 +/- 64 +/- 4096 +/- 8192 +/- 262144 +/- 16777216 +/- 1073741824
128 +/- 128 +/- 16384 +/- 32768 +/- 2097152 +/- 268435456
256 +/- 256 +/- 65536 +/- 131072 +/- 16777216
Result can overflow on full scale
input (> 32-bit signed integer)
1024 +/- 1024 +/- 1048576 +/- 2097152 +/- 1073741824
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