Industrial V/I Converter and Protector IC

AM462

Analog Microelectronics GmbH

An der Fahrt 13, D – 55124 Mainz

Oktober 2007 – Rev.2.5 -Page 16/20

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

Fax: +49 (0)6131/91 073-30

Internet:

http://www.analogmicro.de

Email: info@analogmicro.de

Using Equation (13) the following applies:

157

.

0

V

456

.

3

V

456

.

3

V

4

6

6

7

6

≈

−

=

∆

∆

−

∆

=

PIN

PIN

IN

V

V

V

R

R

⇒

6

7

35

.

6

R

R

⋅

=

According to Equation (14) the minimum output current generated by the input offset is calculated

as:

mA

2

27

8

1

1

6.37

6,37

V

5

.

0

8

1

0

7

6

7

min

min

≈

Ω

⋅

⋅

+

⋅

=

⋅

+

⋅

=

R

R

R

R

V

I

IN

OUT

To obtain an output current of IOUT = 4...20mA, according to the above a current of ISET = 2mA must

then be added. With reference to Equation (5) the ratio of R3 to R4 is calculated thus:

4

3

4

0

!

2

mA

2

R

R

R

R

V

I

REF

SET

+

⋅

=

=

⇒

3

.

45

1

mA

2

27

2

V

5

1

2

0

4

3

≈

−

⋅

Ω

⋅

=

−

=

SET

REF

I

R

V

R

R

Observing the given boundary conditions, the following values are obtained for the external

components:

R0 = 27Ω

R6 ≈ 10kΩ

R7 = 63.7kΩ

R3 = 90.6kΩ

R4 = 2kΩ

R5 = 39Ω

RL = 0...600Ω

C1 = 2.2µF

R9 = 47 kΩ

Ground

R

5

R

L

1

Signal-ended

input voltage

Connections setting unused funktion blocks in a defined operating point

3-wire connection

V

BG

1

2

AM462

OP2

R

7

R

9

4

OP1

5

3

R

3

C

1

R

0

14

6

13

15

16

11

8

9

10

V

I

R

4

T

1

D

1

Voltage reference

V

S

I

OUT

R

6

V

IN

Figure 9:

Converting an input signal with an input signal offset (3-wire-application)