AD210 L-COM, AD210 Datasheet - Page 7

• Manufacturer Part Number: AD210
• Description: FOM100 SERIES UNIV LC ADPTR
• Manufacturer: L-COM

lent current V
gain temperature coefficient, and must be of suitable stability for
the application. The external low power op amp, powered by
+V
common. All the current flowing through the 2 k resistor flows
through the output Darlington pass devices. A Darlington con-
figuration is used to minimize loss of output current to the base.
The low leakage diode is used to protect the base-emitter junc-
tion against reverse bias voltages. Using –V
return allows more than 10 V of compliance. Offset and gain
control may be done at the input of the AD210 or by varying
the 2 k resistor and summing a small correction current
directly into the summing node. A nominal range of 1 mA–
5 mA is recommended since the current output cannot reach
zero due to reverse bias and leakage currents. If the AD210 is
powered from the input potential, this circuit provides a fully
isolated, wide bandwidth current output. This configuration is
limited to 5 mA output current.
Isolated V-to-I Converter
Illustrated in Figure 19, the AD210 is used to convert a 0 V to
+10 V input signal to an isolated 4–20 mA output current. The
AD210 isolates the 0 V to +10 V input signal and provides a
proportional voltage at the isolator’s output. The output circuit
converts the input voltage to a 4–20 mA output current, which
in turn is applied to the loop load R
Isolated Thermocouple Amplifier
The AD210 application shown in Figure 20 provides amplifica-
tion, isolation and cold-junction compensation for a standard J
type thermocouple. The AD590 temperature sensor accurately
REV. A
V
V
0-10V
SIG
SIG
Figure 19. Isolated Voltage-to-Current Loop Converter
OSS
Figure 18. Self-Powered Isolated Current Source
17
16
19
18
14
15
and –V
16
17
19
18
14
15
+V
–V
+V
–V
ISS
ISS
ISS
OUT
OSS,
ISS
/2 k . This resistor directly affects the output
+15V
maintains its summing junction at output
+15V
30
30
29
29
AD210
AD210
+V
–V
+V
–V
OSS
OSS
ADJUST
TO 4mA
WITH 0V IN
OSS
OSS
LOAD
1
2
3
4
1
2
3
4
2N2907
2k
3.0k
AD308
.
OSS
SPAN
ADJ
+V
–V
as a current
S
S
LF441
FDH333
+V
–V
1N4149
OSS
OSS
143
500
2N2219
100
R
RETURN
576
CURRENT
CURRENT
LOAD
I
I
OUT
OUT
2N3906
LOOP
LOOP
+28V
(2)
–7–
monitors the input terminal (cold-junction). Ambient tempera-
ture changes from 0 C to +40 C sensed by the AD590, are can-
celled out at the cold junction. Total circuit gain equals 183;
100 and 1.83, from A1 and the AD210 respectively. Calibration
is performed by replacing the thermocouple junction with plain
thermocouple wire and a millivolt source set at 0.0000 V (0 C)
and adjusting R
source to +0.02185 V (400 C) and adjust R
+4.000 V. This application circuit will produce a nonlinearized
output of about +10 mV/ C for a 0 C to +400 C range.
Precision Floating Programmable Reference
The AD210, when combined with a digital-to-analog converter,
can be used to create a fully floating voltage output. Figure 21
shows one possible implementation.
The digital inputs of the AD7541 are TTL or CMOS compat-
ible. Both the AD7541 and AD581 voltage reference are pow-
ered by the isolated power supply + V
input digital common to provide a digital ground reference for
the inputs.
The AD7541 is a current output DAC and, as such, requires an
external output amplifier. The uncommitted input amplifier
internal to the AD210 may be used for this purpose. For best
results, its input offset voltage must be trimmed as shown.
The output voltage of the AD210 will go from 0 V to –10 V for
digital inputs of 0 and full scale, respectively. However, since
the output port is truly isolated, V
interchanged to get 0 V to +10 V.
This circuit provides a precision 0 V–10 V programmable refer-
ence with a 3500 V common-mode range.
JUNCTION
THERMAL
CONTACT
DIGITAL
Figure 21. Precision Floating Programmable Reference
"J"
12-BIT
INPUT
COLD
–V
OR EQUIVALENT
HP5082-2811
AD590
R
ISS
G
GAIN
-20k-
52.3
10k
Figure 20. Isolated Thermocouple Amplifier
15
4
+V
17
–V
ISS
ISS
+V
3
16
ISS
2k
18
O
1
2
R
AD OP-07
1k
5k
G
for E
A1
220pF
AD581
100k
+V
13.7k
ISS
OFFSET
OUT
1000pF
50k
10k
1k
100k
200
equal to 0.000 V. Set the millivolt
17
19
18
14
15
16
19
14
15
16
17
18
+V
–V
+V
–V
OUT
ISS
ISS
ISS
ISS
ISS
and O
. I
+15V
+15V
30
30
COM
G
COM
for V
29
29
should be tied to
may be freely
AD210
AD210
AD210
+V
–V
OUT
+V
–V
OSS
OSS
OSS
OSS
equal to
1
2
3
4
1
0 - –10V
2
3
4
V
V
OUT
OUT