AD628
+12V
–12V
0.1μF
10μF
0.1μF
10μF
2
7
+Vs
–Vs
–IN
8
AD628
10kΩ
A1
100kΩ
100kΩ
SERIAL DATA
+/–10V
SCLK
SDATA
CS
4
5
6
10kΩ
+IN
1
49.9Ω
AD7940
3
A2
V
5
IN
V
GND
2
DD
33nF
10kΩ
1
V
C
FILT
REF
R
G
6
3
4
10μF
0.1μF
R
EXT1
15kΩ
15nF
V
V
IN
OUT
+12V
2
3
REF195
4
0.1μF
10μF
R
10kΩ
EXT2
8
5
6
2
AD8606
2/2
7
AD8606
1/2
1
AD628 REFERENCE VOLTAGE
4
3
10kΩ
10kΩ
Figure 32. Level Shifter
MONITORING BATTERY VOLTAGES
CURRENT LOOP RECEIVER
Figure 34 illustrates how the AD628 is used to monitor a battery
charger. Voltages approximately eight times the power supply
voltage can be applied to the input with no damage. The resistor
divider action is well-suited for the measurement of many
power supply applications, such as those found in battery
chargers or similar equipment.
Analog data transmitted on a 4 to 20 mA current loop can be
detected with the receiver shown in Figure 33. The AD628 is an
ideal choice for such a function because the current loop is
driven with a compliance voltage sufficient to stabilize the loop,
and the resultant common-mode voltage often exceeds com-
monly used supply voltages. Note that with large shunt values, a
resistance of equal value must be inserted in series with the
inverting input to compensate for an error at the noninverting
input.
V
= 15V
+15V –15V
CM
3
7
2
4
AD628
10kΩ
249Ω
100kΩ
1
8
10kΩ
0V TO 5V
TO ADC
5
249Ω
100kΩ
10kΩ
6
I = 4 TO 20mA
210kΩ
100kΩ
9.53kΩ
+2.5V
Figure 33. Level Shifter for 4 to 20 mA Current Loop
Rev. F | Page 17 of 20
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