Industrial V/I Converter and Protector IC

AM462

analog microelectronics

December2006

Analog Microelectronics GmbH

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

8/20

An der Fahrt 13, D – 55124 Mainz

Fax:

+49 (0)6131/91 073 – 30

Rev. 2.4

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

INITIAL OPERATION OF AM462

General information on 2- and 3-wire applications and the use of current

In 3-wire operation (cf. Figure 3 right and Figure 7) the ground of the IC (pin GND) is connected up

and pin VCC to pin RS+.

RS+ and pin VCC to RS-. The ground of the IC (pin GND) is connected to the node between resistor

the system ground.

In 2-wire operation the IC ground is "virtual" (floating), as with a constant load resistance the

applies to 2-wire operation:

()

L

IN

OUT

S

CC

R

V

I

V

V

−

=

(2)

The reason for this is that in 2-wire operation the IC is connected in series to the actual load resistor

Setting the output current range

When using amplification stage OP1 together with the V/I converter for voltage-to-current

conversion the offset of the output current should first be compensated for by suitable selection of

short circuit at the input and by connecting up V/I converter pin VSET as shown in Figure 2 the

values of the output current according to Equation 2 are as follows:

R

L

V

S

2-wire system

signal source and

conditioning IC

GND Ground

≠

V

Ground

R

L

3-wire system

signal source and

conditioning IC

GND Ground

=

V

Ground GND

=

GND

V

CC

I

OUT

I

OUT

VV

CC

S

=

Figure 3: The difference between 2- and 3-wire operation