Analog Devices AD7194 Manual page 40

AD7194
When the analog input is constant or a channel change occurs,
valid conversions are available at a constant output data rate.
When conversions are being performed on a single channel and
a step change occurs on the analog input, the ADC continues to
output fully settled conversions if the step change is synchronized
with the conversion process. If the step change is asynchronous,
one conversion is output from the ADC, which is not completely
settled (see Figure 30).
ANALOG
INPUT
ADC
OUTPUT
Figure 30. Sinc
Table 29 shows examples of output data rate and the corres-
ponding FS values.
Table 29. Examples of Output Data Rates and the
Corresponding Settling Time (Zero Latency)
FS[9:0] Output Data Rate (Hz)
480 2.5
96 12.5
80 15
4
Sinc 50 Hz/60 Hz Rejection
Figure 31 shows the frequency response of the sinc
FS[9:0] is set to 96 and the master clock is 4.92 MHz. With zero
latency disabled, the output data rate is equal to 50 Hz. With
zero latency enabled, the output data rate is 12.5 Hz. The sinc
filter provides 50 Hz (±1 Hz) rejection in excess of 120 dB
minimum, assuming a stable master clock.
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0 25
Figure 31. Sinc
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FULLY
SETTLED
f
1/
ADC
4
Zero Latency Operation
Settling Time (ms)
400
80
66.6
4
filter when
50 75 100 125
FREQUENCY (Hz)
4
Filter Response (FS[9:0] = 96)
Figure 32 shows the frequency response when FS[9:0] is
programmed to 80 and the master clock is equal to 4.92 MHz.
The output data rate is 60 Hz when zero latency is disabled and
15 Hz when zero latency is enabled. The sinc
60 Hz (±1 Hz) rejection of 120 dB minimum, assuming a stable
master clock.
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
Simultaneous 50 Hz and 60 Hz rejection is obtained when
FS[9:0] is programmed to 480 and the master clock equals
4.92 MHz. The output data rate is 10 Hz when zero latency is
disabled and 2.5 Hz when zero latency is enabled. The sinc
filter provides 50 Hz (±1 Hz) and 60 Hz (±1 Hz) rejection of
120 dB minimum, assuming a stable master clock.
0
–10
4
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
Simultaneous 50 Hz/60 Hz rejection can also be achieved using
the REJ60 bit in the mode register. When FS[9:0] is set to 96
150
and REJ60 is set to 1, notches are placed at 50 Hz and 60 Hz.
Rev. 0 | Page 40 of 56
30 60 90
FREQUENCY (Hz)
4
Figure 32. Sinc Filter Response (FS[9:0] = 80)
30 60 90
FREQUENCY (Hz)
4
Figure 33. Sinc Filter Response (FS[9:0] = 480)
4
filter provides
120 150
4
120 150