Figure 74. Example: Sinc3 Filter Response - ST STM32F412 Reference Manual

Digital filter for sigma delta modulators (DFSDM)
reach the required output data rates and required output data resolution. The configurable
parameters are:
•
Filter order/type: (see FORD[2:0] bits in DFSDM_FLTxFCR register):
–
–
–
–
–
–
•
Filter oversampling/decimation ratio (see FOSR[9:0] bits in DFSDM_FLTxFCR
register):
–
–
–
The filter has the following transfer function (impulse response in H domain):
•
Sinc
• FastSinc filter type:
366/1163
FastSinc
1
Sinc
2
Sinc
3
Sinc
4
Sinc
5
Sinc
FOSR = 1-1024 - for FastSinc filter and Sinc
FOSR = 1-215 - for Sinc
FOSR = 1-73 - for Sinc
x
filter type:
H z ( )
H z ( )
Figure 74. Example: Sinc
x
filter x = F
ORD
x
filter x = F
ORD
x
– FOSR
 
1 z
–
---------------------------- -
=  
– 1
 
1 z
–
2
– FOSR
 
1 z –
---------------------------- - ⋅ (
=   1 +
– 1
 
1 z
–
3
filter response
Normalized frequency (f
RM0402 Rev 6
x
filter x = F = 1..3
ORD
= 4
= 5
( ⋅ )
– 2 FOSR
)
z
/f )
IN DATA
MS30770V1
RM0402