am452 AME, Inc., am452 Datasheet - Page 15

• Manufacturer Part Number: am452
• Description: Voltage-to-current Transducer Ic With A Differential Input - Analog Microelectronics
• Manufacturer: AME, Inc.

Figure 6: 3-wire application for differential input signals
Due to the algorithm upon which it is based the program also accounts for the spec. tolerances
of the IC and the components connected to it.
APPLICATIONS
Typical 3-wire application with a differential input signal
The aim of the calculation is the dimensioning of resistors R
In 3-wire operation (see Figure 6) the IC's connection to ground (pin 14 or GND) is connected
to the system ground (Ground) which is applied externally. System supply voltage V
connected to pin 10 or VCC and pin VCC to pin 11 or RS+. In this configuration AM452's
quiescent current does then not flow via resistor R
Figure 6 depicts the 3-wire application in which the differential output signal of a measuring
bridge supplied with current is amplified and converted. Power is supplied to the measuring
bridge by operational amplifier OP2 (c.f.: Using OP2 as a current source).
It is assumed in this application that no negative differential input voltages occur. Pin 13 (ZA)
is thus connected to the IC ground GND.
According to Equations (9) and (10) the following applies to output current I
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
R
AM452 – Voltage-to-current transducer IC
SET
2
4
3
V
BG
AM452
ZERO Stage
OP2
IA
mit
I
13
OUT
G
1
I
V
Voltage Reference
IN
G
with a differential input
12
5
8
C
IA
G
R
R
1
OP1
2
I
G
0
GAIN
15
R
I
1
SET
R
3
16
7
5
mit
1
R
G
G
4
V
SET
VI
ZA
R
R
V/I Converter
SET Stage
1
2
0
und
I
0
14
3-wire-connection
SET
.
GND
11
10
9
8
V
2
R
REF
5
R
T
0
1
D
0
R
Ground
1
Phone: [phone]
Fax:
Internet:
Email: [e-mail]
to R
0
February 2008 - Rev 1.2 - Page 15/21
I
R
R
V
OUT
L
S
3
R
5
.
4
R
+49 (0)6131/91 073-30
http://www.analogmicro.de
4
Figure 6 illustrates a
typical 3-wire circuit
with a positive,
differential input
signal which can be
used for calibrated
sensing elements, for
example. The offset
current is set using the
SET stage and the full
scale via the gain at
OP1.
OUT
:
(11)
(12)
S
is