Datasheet

AD7608 Data Sheet
Rev. A | Page 28 of 32
OVERSAMPLING BY 64
0
1000
2000
3000
4000
6000
5000
7000
–1 0
CODE
1
NUMBER OF OCCURENCES
08938-150
465
6489
1238
Figure 52. Histogram of Codes—OS × 64 (3 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 53 to Figure 58 show the digital filter frequency profiles
for oversampling by 2 to oversampling by 64. 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 AD7608. 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
08938-151
Figure 53. Digital Filter OS × 2
0
–10
–20
–30
–40
–50
–60
–70
–80
100 1k 10k 100k 10M1M
–100
–90
ATTENUATION (dB)
FREQUENCY (Hz)
AV
CC
= 5V
V
DRIVE
= 5V
T
A
= 25°C
±10V RANGE
OS BY 4
08938-152
Figure 54. Digital Filter Response for OS × 4
0
–10
–20
–30
–40
–50
–60
–70
–80
100 1k 10k 100k 10M1M
–100
–90
ATTENUATION (dB)
FREQUENCY (Hz)
AV
CC
= 5V
V
DRIVE
= 5V
T
A
= 25°C
±10V RANGE
OS BY 8
08938-153
Figure 55. Digital Filter Response for OS × 8
0
–10
–20
–30
–40
–50
–60
–70
–80
100 1k 10k 100k 10M1M
–100
–90
ATTENUATION (dB)
FREQUENCY (Hz)
AV
CC
= 5V
V
DRIVE
= 5V
T
A
= 25°C
±10V RANGE
OS BY 16
08938-154
Figure 56. Digital Filter Response for OS × 16