Datasheet

AD7609 Data Sheet
Rev. A | Page 30 of 36
OVERSAMPLING BY 16
0
500
1000
1500
2000
3000
4000
2500
3500
4500
–2–3 –1 0
CODE
1 2
385
NUMBER OF OCCURENCES
09760-048
3
406
3279
3833
657
14
Figure 51. Histogram of Codes—OS × 16 (Six Codes)
45
5090
341
OVERSAMPLING BY 32
0
1000
2000
3000
4000
5000
6000
–2 –1
CODE
0 1
NUMBER OF OCCURENCES
09760-049
2716
Figure 52. Histogram of Codes—OS × 32 (Four Codes)
1
5871
75
OVERSAMPLING BY 64
0
1000
2000
3000
4000
6000
5000
7000
–2 –1
CODE
0 1
NUMBER OF OCCURENCES
09760-050
2245
Figure 53. Histogram of Codes – OS × 64 (Four Codes)
When the oversampling mode is selected, this has the effect
of adding a digital filter function after the ADC. The different
oversampling rates and the CONVST x sampling frequency
produces different digital filter frequency profiles.
Figure 54 to Figure 59 show the digital filter frequency profiles
for the different oversampling rates. The combination of the
analog antialiasing filter and the oversampling digital filter can
be used to eliminate or reduce the complexity of the design of
the filter before the AD7609. The digital filtering combines
steep roll-off and linear phase response.
0
–10
–20
–30
–40
–50
–60
–70
–80
100 1k 10k 100k 10M1M
–90
ATTENUATION (dB)
FREQUENCY (Hz)
AV
CC
= 5V
V
DRIVE
= 5V
T
A
= 25°C
10V RANGE
OS BY 2
09760-051
Figure 54. Digital Filter Response for OS × 2
0
–10
–20
–30
–40
–50
–60
–70
–80
100 1k 10k 100k 10M1M
–100
–90
ATTENUATION (dB)
FREQUENCY (Hz)
09760-052
AV
CC
= 5V
V
DRIVE
= 5V
T
A
= 25°C
10V RANGE
OS BY 4
Figure 55. Digital Filter Response for OS × 4