am422 AME, Inc., am422 Datasheet - Page 8

• Manufacturer Part Number: am422
• Description: Voltage/current Converter - Analog Microelectronics
• Manufacturer: AME, Inc.

VOLTAGE/CURRENT CONVERTER
TYPICAL THREE–WIRE APPLICATION (0 – 5/10V)
Used in a three–wire circuit (AM422–1) ground pin 7 (GND) is connected to Ground (Figure 7).
The relationship of R
The current I
With R
Example 1: Output current range 4...20mA
In this case the values of the external devices (V
R
R
Example 2: Output current range 0...20mA
In this case the values of the external devices (V
R
R
analog microelectronics
Figure 7
0
1
0
1
R
/R
/R
V
= 25Ω
= 25Ω
SET
IN
R
2
2
4
≈ 5.25
≈ 9
3
R
1
= R
R
2
V
SET
4
SET
the set resistor R
4
5
AM4221
is used to set the output current offset and can be calculated by using equation 3
I
R
R
R
V
SET
SET
1
2
REF
2
=
(
1
V
/R
≈
2
IN
R
R
R
R
2
R I
4
, using equation 2, becomes
3
L
3
L
0
R R I
=
= R
= R
= 0...500Ω
= 0...500Ω
(
0
Amplifier
V
0
G = 1
OUTmax
)
REF
V
SET
4
4
4
=
INmax
= 33kΩ
= 33kΩ
V
SET
becomes (equation 4)
R
REF
0
−
V
OFFSET
I
⋅
R
SET
7
2
3
(
(
R
R
)
4
3
−
+
+
1
R
V
R
5/10 V Reference
SET
R
C
R
C
4
IN
IN
6
SET
SET
1
1
+
= 2.2µF
= 2.2µF
)
= 0 10
= 0 5
R
−
≈ 2.64kΩ
= 0Ω
SET
 V , V
V
R
 V , V
REF
3
)
8
I
REF
C
REF
1
= 5V ) are as follows
= 5V ) are as follows
1
2
3
R
R
5
5
= 40Ω
= 40Ω
T
1
D
R
1
0
R
5
Ground
AM422
I
OUT
V
R
S
L
April 99
8/10