Datasheet

CM +V
REF
+V
REF
-V
REF
Single-EndedInputs
t
+IN
CM Voltage
CM V-
REF
CM +1/2V
REF
DifferentialInputs
t
+IN
-IN
CM Voltage
CM 1/2V-
REF
-IN=CMVoltage
+V
REF
-V
REF
Common−mode voltage (Differential mode) =
(+IN) ) (−IN)
2
. Common−mode voltage (Single−ended mode) = −IN
2.7
2.3
AV =5V
DD
3.8
1.2
5
4
3
2
1
0
1-
Single-EndedInput
Common-ModeVoltageRange(V)
1.0 1.5 2.0 2.5 3.0
V (V)
REF
2.6
5
4
3
2
1
0
1-
Common-ModeVoltageRange(V)
DifferentialInput
AV =5V
DD
4.0
0.45
4.55
1.0 1.5 2.0 2.5 3.0
V (V)
REF
2.6
1.0
ADS8365
www.ti.com
.................................................................................................................................................... SBAS362C AUGUST 2006 REVISED MARCH 2008
NOTES:
The maximum differential voltage between +IN and IN of the ADS8365 is V
REF
. See Figure 23 and Figure 24 for a
further explanation of the common voltage range for single-ended and differential inputs.
Figure 22. Using the ADS8365 in the Single-Ended and Differential Input Modes
Figure 23. Single-Ended Input: Common-Mode Figure 24. Differential Input: Common-Mode
Voltage Range vs V
REF
Voltage Range vs V
REF
When the input is differential, the amplitude of the In each case, care should be taken to ensure that the
input is the difference between the +IN and IN input, output impedance of the sources driving the +IN and
or: (+IN) ( IN). The peak-to-peak amplitude of each IN inputs are matched. Often, a small capacitor
input is ± 1/2V
REF
around this common voltage. (20pF) between the positive and negative input helps
However, since the inputs are 180 ° out-of-phase, the to match the impedance. Otherwise, a mismatch may
peak-to-peak amplitude of the differential voltage is result in offset error, which will change with both
+V
REF
to V
REF
. The value of V
REF
also determines temperature and input voltage.
the range of the voltage that may be common to both
The input current on the analog inputs depends on a
inputs, as shown in Figure 24 .
number of factors, such as sample rate or input
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