AD210
INSIDE THE AD210
The AD210 basic block diagram is illustrated in Figure 1.
A +15 V supply is connected to the power port, and
±
15 V isolated power is supplied to both the input and
output ports via a 50 kHz carrier frequency. The uncom-
mitted input amplifier can be used to supply gain or buff-
ering of input signals to the AD210. The fullwave
modulator translates the signal to the carrier frequency for
application to transformer T1. The synchronous demodu-
lator in the output port reconstructs the input signal. A
20 kHz, three-pole filter is employed to minimize output
noise and ripple. Finally, an output buffer provides a low
impedance output capable of driving a 2 kΩ load.
FB
–IN
+IN
I
COM
+V
ISS
–V
ISS
16
17
19
18
14
15
T2
INPUT
POWER
SUPPLY
POWER
OSCILLATOR
30
PWR
29
PWR COM
POWER
T3
OUTPUT
POWER
SUPPLY
3
4
+V
OSS
INPUT
T1
MOD
DEMOD
FILTER
1
V
O
OUTPUT
R
F
16
17
V
SIG
R
G
18
19
1
V
OUT
R
= V
SIG
1+
F
R
G
(
)
AD210
2
14
15
+V
ISS
–V
ISS
30
+15V
29
+V
OSS
–V
OSS
3
4
Figure 3. Input Configuration for G > 1
Figure 4 shows how to accommodate current inputs or sum cur-
rents or voltages. This circuit configuration can also be used for
signals greater than
±
10 V. For example, a
±
100 V input span
can be handled with R
F
= 20 kΩ and R
S1
= 200 kΩ.
I
S
R
F
16
17
1
V
OUT
2
+V
ISS
–V
ISS
30
V
S1
+15V
29
2
O
COM
–V
OSS
R
S2
V
S2
R
S1
V
S1
19
AD210
AD210
18
14
15
Figure 1. AD210 Block Diagram
+V
OSS
–V
OSS
3
4
USING THE AD210
The AD210 is very simple to apply in a wide range of ap-
plications. Powered by a single +15 V power supply, the
AD210 will provide outstanding performance when used
as an input or output isolator, in single and multichannel
configurations.
Input Configurations:
The basic unity gain configura-
tion for signals up to
±
10 V is shown in Figure 2. Addi-
tional input amplifier variations are shown in the following
figures. For smaller signal levels Figure 3 shows how to
obtain gain while maintaining a very high input impedance.
16
17
V
SIG
±10V
19
1
V
OUT
V
OUT
(±10V)
2
+V
ISS
–V
ISS
30
+15V
29
V
OUT
= –R
F
(
R
S1
+ R
S2
S2
V
+ I
S
+ ...
)
Figure 4. Summing or Current Input Configuration
Adjustments
When gain and offset adjustments are required, the actual cir-
cuit adjustment components will depend on the choice of input
configuration and whether the adjustments are to be made at
the isolator’s input or output. Adjustments on the output side
might be used when potentiometers on the input side would
represent a hazard due to the presence of high common-mode
voltage during adjustment. Offset adjustments are best done at
the input side, as it is better to null the offset ahead of the gain.
Figure 5 shows the input adjustment circuit for use when the in-
put amplifier is configured in the noninverting mode. This offset
adjustment circuit injects a small voltage in series with the
GAIN
47.5kΩ
16
5kΩ
17
19
V
SIG
R
G
HI
LO
200Ω
14
100kΩ
50kΩ
OFFSET
15
–V
ISS
30
+15V
29
–V
OSS
4
+V
ISS
+V
OSS
3
18
1
V
OUT
AD210
18
14
15
+V
OSS
–V
OSS
3
4
Figure 2. Basic Unity Gain Configuration
AD210
2
The high input impedance of the circuits in Figures 2 and
3 can be maintained in an inverting application. Since the
AD210 is a three-port isolator, either the input leads or
the output leads may be interchanged to create the signal
inversion.
Figure 5. Adjustments for Noninverting Input
REV. A
–3–
AD [ ANALOG DEVICES ]
