Datasheet

ADC
SENSOR
INPUT
NETWORK
FEEDBACK
NETWORK
V
-
V
+
SENSOR
INPUT
NETWORK
FEEDBACK
NETWORK
V
-
ADC
(a)
(b)
R
ISO
C
V
+
LMP7731
www.ti.com SNOSAT6E –JULY 2007–REVISED MARCH 2013
ADC's sampling capacitor. Since this large capacitor will be loading the output of the amplifier as well, an
isolation resistor is needed between the output of the amplifier and this capacitor. The isolation resistor, R
ISO
,
separates the additional load capacitance from the output of the amplifier and will also form a low-pass filter and
can be designed to provide noise reduction as well as anti-aliasing. The drawback to having R
ISO
is that it
reduces signal swing since there is some voltage drop across it.
Figure 49 (a) shows the ADC directly connected to the amplifier. To minimize the glitch in this setting, a slower
sample rate needs to be used. Figure 49 (b) shows R
ISO
and an external capacitor used to minimize the glitch.
Figure 49. Driving an ADC
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