Datasheet
ADS8326
0Vto+V
REF
Peak-to-Peak
Common-Mode
Voltage
2 3 4 5 6
V (V)
REF
CommonVoltageRange(V)
-1
0
1
-0.3
0.5
4.8
2.5
V =5V
DD
Common-ModeVoltage +V
REF
+V
REF
t
+IN
Common-Mode Voltage
-IN=Common-ModeVoltage
ADS8326
SBAS343C –MAY 2007–REVISED SEPTEMBER 2009..................................................................................................................................................
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ANALOG INPUT
The analog input of ADS8326 is differential. The +IN
and –IN input pins allow for a differential input signal.
The amplitude of the input is the difference between
the +IN and –IN input, or (+IN) – (–IN). Unlike some
converters of this type, the –IN input is not resampled
later in the conversion cycle. When the converter
goes into Hold mode or conversion, the voltage
Figure 38. Methods of Driving the ADS8326
difference between +IN and –IN is captured on the
internal capacitor array.
The range of the –IN input is limited to –0.3V to
+0.5V. As a result of this limitation, the differential
input could be used to reject signals that are common
to both inputs in the specified range. Thus, the –IN
input is best used to sense a remote signal ground
that may move slightly with respect to the local
ground potential.
The general method for driving the analog input of the
ADS8326 is shown in Figure 38 and Figure 40. The
–IN input is held at the common-mode voltage. The
+IN input swings from –IN (or common-mode voltage)
to –IN + V
REF
(or common-mode voltage + V
REF
),
and the peak-to-peak amplitude is +V
REF
. The value
of V
REF
determines the range over which the
Figure 39. +IN Analog Input: Common-Mode
common-mode voltage may vary, as shown in
Voltage Range vs V
REF
Figure 39. Figure 6 and Figure 7 (+5V), and
Figure 25 and Figure 26 (+2.7V) illustrate the typical
change in gain and offset as a function of the
common-mode voltage applied to the –IN pin.
NOTE: The maximum differential voltage between +IN and –IN of the ADS8326 is V
REF
. See Figure 39 for a further
explanation of the common-mode voltage range for differential inputs.
Figure 40. Differential Input Mode of the ADS8326
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