AD628
5V
+V
S
nV
(V)
–IN
100kΩ
100kΩ
10kΩ
10kΩ
BAT
0V TO 5V
TO ADC
+IN
–IN
OUT
A2
G = +0.1
A1
R
10kΩ
–IN
+IN
EXT1
CHARGING
CIRCUIT
+1.5V
BATTERY
R
G
+IN
OTHER
BATTERIES IN
CHARGING
CIRCUIT
10kΩ
AD628
–V
V
C
FILT
S
REF
Figure 34. Battery Voltage Monitor
FILTER CAPACITOR VALUES
KELVIN CONNECTION
Connect a capacitor to Pin 4 (CFILT) to implement a low-pass
filter. The capacitor value is
In certain applications, it may be desirable to connect the
inverting input of an amplifier to a remote reference point.
This eliminates errors resulting in circuit losses in interconnect-
ing wiring. The AD628 is particularly suited for this type of
connection. In Figure 35, a 10 kΩ resistor added in the feedback
matches the source impedance of A2. This is described in more
detail in the Gain Adjustment section.
C = 15.9/ft
(
ꢁF
)
where ft is the desired 3 dB filter frequency.
Table 7 shows several frequencies and their closest standard
capacitor values.
5V
Table 7. Capacitor Values for Various Filter Frequencies
+V
S
Frequency (Hz)
Capacitor Value (μF)
–IN
100kΩ
100kΩ
10kΩ
10kΩ
CIRCUIT
LOSS
10
50
60
100
400
1 k
5 k
10 k
1.5
0.33
0.27
0.15
0.039
0.015
0.0033
0.0015
+IN
A2
–IN
OUT
G = +0.1
A1
–IN
+IN
10kΩ
R
G
LOAD
+IN
10kΩ
AD628
V
–V
REF
C
FILT
S
V
/2
S
Figure 35. Kelvin Connection
Rev. F | Page 18 of 20
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