Datasheet

ADS8364
11
SBAS219C
www.ti.com
When the input is differential, the amplitude of the input is the
difference between the +IN and –IN input, or: (+IN) – (–IN).
The peak-to-peak amplitude of each input is ±1/2V
REF
around
this common voltage. However, since the inputs are 180°
out-of-phase, the peak-to-peak amplitude of the differential
voltage is +V
REF
to –V
REF
. The value of V
REF
also determines
the range of the voltage that may be common to both inputs,
as shown in Figure 4.
FIGURE 2. Using the ADS8364 in the Single-Ended and Differential Input Modes.
FIGURE 3. Single-Ended Input: Common-Mode Voltage
Range vs V
REF
.
FIGURE 4. Differential Input: Common-Mode Voltage
Range vs V
REF
.
In each case, care should be taken to ensure that the output
impedance of the sources driving the +IN and –IN inputs are
matched. Often, a small capacitor (20pF) between the posi-
tive and negative input helps to match their impedance.
Otherwise, this may result in offset error, which will change
with both temperature and input voltage.
The input current on the analog inputs depends on a number
of factors as sample rate or input voltage. Essentially, the
CM + V
REF
+V
REF
–V
REF
Single-Ended Inputs
t
+IN
CM
Voltage
CM
– V
REF
CM + 1/2V
REF
Differential Inputs
NOTES: Common-Mode Voltage (Differential Mode) = , Common-Mode Voltage (Single-Ended Mode) = IN–.
(+IN) + (–IN)
2
The maximum differential voltage between +IN and –IN of the ADS8364 is V
REF
. See Figures 3 and 4 for a further
explanation of the common voltage range for single-ended and differential inputs.
t
+IN
–IN
CM
Voltage
CM
– 1/2V
REF
–IN = CM Voltage
+V
REF
–V
REF
1.0 1.5 2.0 2.5
2.6
3.0
V
REF
(V)
Common Voltage Range (V)
–1
0
1
2
3
4
5
2.7
2.3
3.8
1.2
AV
DD
= 5V
Single-Ended Input
1.0 1.5 2.0 2.5
2.6
3.0
V
REF
(V)
Common Voltage Range (V)
–1
0
1
2
3
4
5
4.55
0.45
AV
DD
= 5V
4.0
1.0
Differential Input