AM452 – Voltage-to-current transducer IC

with a differential input

Analog Microelectronics GmbH

An der Fahrt 13, D – 55124 Mainz

February 2008 - Rev 1.2 - Page 11/21

Phone: +49 (0)6131/91 073-0

Fax:

+49 (0)6131/91 073-30

Internet: http://www.analogmicro.de

Email: info@analogmicro.de

Differences in the AM452 circuitry with 2- and 3-wire applications

Figure 4: Differences in 2-and 3-wire circuitry in conjunction with AM452

AM452 is constructed in such a way that by changing the external circuitry it is suitable for

both 2-wire and 3-wire operation.

In 3-wire operation (see Figure 4, right) the IC's connection to ground (pin 14 or GND) is

connected to the system ground (Ground) which is applied externally. System supply voltage

VS is connected to pin 10 (VCC) and pin VCC to pin 11 (RS+). Supply current ICC then flows

directly into AM452 (power consumption).

In 2-wire operation (see Figure 4, left) system supply voltage VS is connected to pin 11 (RS+)

and pin 10 (VCC) to pin 9 (RS-). The overall current including the supply current then flows

via R0, enabling the relevant voltage drop to be used to regulate transistor T1.

The IC's connection to ground pin 14 (GND) is contacted to the node between resistor R5 and

load resistor RL (current output IOUT). IC ground GND is thus not the same as the ground of

the system (Ground). The output signal is tapped via load resistor RL which links system

output IOUT to the ground of the system.

Ground

V

S

I

OUT

R

0

T

1

D

1

R

5

R

L

GND

14

11

9

8

10

SET Stage

3-wire connection

V/I Converter

Ground

V

S

I

OUT

R

0

T

1

D

1

R

5

R

L

2-wire

connection

C

2

GND

14

11

9

8

10

V/I Converter

SET Stage