Datasheet

Industrial V/I Converter and Protector IC
AM462
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz Oktober 2007 – Rev.2.5 -Page 14/20
Phone: [phone]
Fax: [phone]
Internet:
http://www.analogmicro.de
Email: info@analogmicro
.de
Example : 4…20mA Voltage-To-Current Converter in 2-wire application
To convert a signal of V
INP
= 0...1V at the OP1 input the external components are to be dimensioned
in such a way that the output current has a range of 4...20mA. The following applies:
mA4
88
00
+⋅=+⋅=
R
G
VI
R
G
VI
GAIN
INPSET
GAIN
INPOUT
With R
0
= 27Ω and I
SET
= 4mA. Equation(4) produces the following relation between resistor R
3
and R
4
:
15.221
mA4272
V5
1
2
04
3
≈−
⋅Ω⋅
=−=
SET
REF
IR
V
R
R
and thus the following value for the gain:
456.3
V1
mA16
2788
max
0
=⋅Ω⋅=
−
=
INP
SETOUT
GAIN
V
II
RG ⇒
456.21456.3
2
1
=−=
R
R
Observing the given boundary conditions, the following values are obtained for the external
components:
R
1
≈ 24.56kΩ R
2
= 10kΩ R
3
≈ 44.3kΩ R
4
= 2kΩ
R
0
= 27Ω R
5
= 39Ω R
L
= 0...600Ω C
1
= 2.2µF C
2
= 100nF
Grou nd
T
1
D
1
R
5
R
L
1
Single-ended
input voltage
Connections setting unused function blocks to a defined operating point
1
2
AM462
OP2
R
1
R
2
4
OP1
5
3
R
3
C
1
R
0
14
6
13
15
16
IC ground: GND
System ground: Ground
}
different
potentials!
GND
2-wire
connection
C
2
8
9
11
10
V
R
4
I
Voltage Reference
V
IN P
V
S
I
OUT
V
BG
Figure 8: Typical 2-wire operation for input signals referenced to ground