Datasheet AD210 (Analog Devices) - 4

AD210 R INSIDE THE AD210 F 16 VOUT
The AD210 basic block diagram is illustrated in Figure 1. = V
SIG 1+
( )
RF R 1 G
A +15 V supply is connected to the power port, and
17
±15 V isolated power is supplied to both the input and
V 19 SIG
output ports via a 50 kHz carrier frequency. The uncom-
RG AD210 2
mitted input amplifier can be used to supply gain or buff-
18
ering of input signals to the AD210. The fullwave
14 +V
modulator translates the signal to the carrier frequency for
ISS +VOSS 3
application to transformer T1. The synchronous demodu-
15 –VISS –V 4
lator in the output port reconstructs the input signal. A
OSS 30 29
20 kHz, three-pole filter is employed to minimize output noise and ripple. Finally, an output buffer provides a low
+15V
impedance output capable of driving a 2 kΩ load. Figure 3. Input Configuration for G > 1 Figure 4 shows how to accommodate current inputs or sum cur-
INPUT OUTPUT FB 16 T1
rents or voltages. This circuit configuration can also be used for signals greater than ± 10 V. For example, a ± 100 V input span
–IN 17 1 V MOD DEMOD O
can be handled with RF = 20 kΩ and RS1 = 200 kΩ.
+IN 19 FILTER ICOM 18 2 OCOM IS RF T3 16 T2 POWER +VISS 14 INPUT OUTPUT 3 +VOSS 1 POWER POWER 17 –V 15 ISS SUPPLY SUPPLY 4 –VOSS RS2 RS1 19 POWER VOUT OSCILLATOR VS2 VS1 AD210 AD210 18 2 30 29 PWR PWR COM 14 +VISS +VOSS 3
Figure 1. AD210 Block Diagram
15 –V –V 4 USING THE AD210 ISS OSS 30 29
The AD210 is very simple to apply in a wide range of ap- plications. Powered by a single +15 V power supply, the
V V +15V S1 S2
AD210 will provide outstanding performance when used
VOUT = –RF
( )
+ + I R S + ... S1 RS2
as an input or output isolator, in single and multichannel Figure 4. Summing or Current Input Configuration configurations.
Adjustments Input Configurations:
The basic unity gain configura- When gain and offset adjustments are required, the actual cir- tion for signals up to ± 10 V is shown in Figure 2. Addi- cuit adjustment components will depend on the choice of input tional input amplifier variations are shown in the following configuration and whether the adjustments are to be made at figures. For smaller signal levels Figure 3 shows how to the isolator’s input or output. Adjustments on the output side obtain gain while maintaining a very high input impedance. might be used when potentiometers on the input side would represent a hazard due to the presence of high common-mode
16
voltage during adjustment. Offset adjustments are best done at the input side, as it is better to null the offset ahead of the gain.
17 1 VOUT 19 VOUT
Figure 5 shows the input adjustment circuit for use when the in-
VSIG (
±
10V)
±
AD210
put amplifier is configured in the noninverting mode. This offset
10V 18 2
adjustment circuit injects a small voltage in series with the
14 +VISS +V GAIN OSS 3 47.5k
Ω
15 –VISS –V 4 16 OSS 5k
Ω
V 30 OUT 29 17 1 19 +15V RG AD210
Figure 2. Basic Unity Gain Configuration
VSIG HI 18 2
The high input impedance of the circuits in Figures 2 and
200
Ω
LO
3 can be maintained in an inverting application. Since the
+V 14 ISS +VOSS 3
AD210 is a three-port isolator, either the input leads or
100k
Ω
50k
Ω the output leads may be interchanged to create the signal
15 –VISS –V 4 OSS OFFSET
inversion.
30 29 +15V
Figure 5. Adjustments for Noninverting Input REV. A –3–