Datasheet

Resolution
100000
10000
1000
100
10
1
0
2 4
6 8 10
12 14
16 18 20
22 24
26 28 30 32
OversamplingRatio
Sinc
1
Sinc
2
Sinc
3
Sincfast
Sinc Filter Unit
AMC1210
SBAS372D – APRIL 2006 – REVISED MAY 2009 .............................................................................................................................................................. www.ti.com
The comparator filter unit and the sinc filter unit differ in the way they handle input data. The comparator filter unit
translates a low input signal to a '0' and a high input signal to a '1', whereas the sinc filter unit uses ' – 1' and '1'.
The resulting calculations give only positive values for the output of the comparator filter. The data representation
is straight binary. Table 9 and Figure 14 show the different full-scale values that the comparator filter can store
using different oversampling ratios.
Table 9. Peak Data Values for Different OSR/Filter Combinations
OSR Sinc
1
Sinc
2
Sinc
3
Sincfast
x 0 to x 0 to x
2
0 to x
3
0 to 2x
2
4 0 to 4 0 to 16 0 to 64 0 to 32
8 0 to 8 0 to 64 0 to 512 0 to 128
16 0 to 16 0 to 256 0 to 4096 0 to 512
32 0 to 32 0 to 1024 0 to 32,768 0 to 2048
Figure 14. Comparator Filter Resolution
The maximum resolution yields the peak values in Table 9 (15 bits binary, 32,768 decimal). Note that in order to
achieve the maximum value, the delta-sigma modulator is operated at absolute maximum positive or negative
full-scale, which is outside of the recommended full-scale range of 80% of most delta-sigma modulators.
The AMC1210 utilizes a standard integration/decimation/differentiation scheme to achieve the sinc filter. It can be
configured as a Sinc
1
, Sinc
2
, Sinc
3
or Sincfast filter with oversampling ratios (OSRs) continuously between 1 and
256. Figure 15 illustrates the frequency response of each type of filter.
18 Submit Documentation Feedback Copyright © 2006 – 2009, Texas Instruments Incorporated
Product Folder Link(s): AMC1210