Datasheet

20
0
20
40
60
80
100
-
-
-
-
-
-
-
120
140
Magnitude(dB)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Frequency(f /f )
IN DATA
0.00005
0.00005
0.00015
0.00025
0.00035
-
-
-
-
Magnitude(dB)
0 0.1 0.2 0.3 0.4 0.5
NormalizedFrequency(f /f )
IN DATA
2
0
2
4
6
8
10
-
-
-
-
-
Magnitude(dB)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
NormalizedFrequency(f /f )
IN DATA
ADS1672
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SBAS402D JUNE 2008REVISED JULY 2010
Phase Response
The low-latency filter uses a multiple stage linear
phase digital filter. Linear phase filters exhibit
constant delay time versus input frequency (also
know as constant group delay). This feature of linear
phase filters means that the time delay from any
instant of the input signal to the corresponding same
instant of the output data is constant and independent
of the input signal frequency. This behavior results in
essentially zero phase error when measuring
multi-tone signals.
WIDE-BANDWIDTH FILTER
The wide-bandwidth (WB) filter is well-suited for
measuring high-frequency ac signals. This digital filter
Figure 30. Frequency Response of
offers excellent passband and stop band
Wide-Bandwidth Filter
characteristics.
blank
The DRATE[1:0] digital input pins select from the four
data rates available with the WB filter, as shown in
Table 7. Note that the START pin must be strobed
after a change to the data rate. If a conversion is in
process during a data rate change, the output data
for that conversion are not valid and should be
discarded.
Table 7. Wide-Bandwidth Data Rates
DRATE DATA RATE –3dB SETTLING TIME,
[1:0] (1/t
DRDY-WB
) BANDWIDTH t
SETTLE-WB
00 78.125kSPS 38kHz 704ms 14061 t
CLK
01 156.25kSPS 76kHz 352ms 7033 t
CLK
10 312.50kSPS 152kHz 176ms 3519 t
CLK
11 625.0kSPS 305kHz 88ms 1762 t
CLK
Figure 31. Passband Response for
While using the wide-bandwidth filter path, the
Wide-Bandwidth Filter
LL_CONFIG pin must be set to logic HIGH. Setting
LL_CONFIG to a logic low forces the ADS1672 to
switch to the low-latency filter path, single cycle
settling mode overriding FPATH pin.
Frequency Response
Figure 30 shows the frequency response for the
wide-bandwidth filter path normalized to the output
data rate, f
DATA
. Figure 31 shows the passband ripple,
and the transition from passband to stop band is
illustrated in Figure 32. These three plots are valid for
all of the data rates available on the ADS1672.
Simply substitute the selected data rate to express
the x-axis in absolute frequency.
Figure 32. Transition Band Response for
Wide-Bandwidth Filter
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