Industrial Converter and Protector IC

AM460

analog microelectronics

April 2003

7/18

AM460 consist of several modular function blocks (operational amplifiers, voltage-to-current converters and

references) which depending on external configurations can either be switched together or operated separately

(see the basic circuitry in Figure 2):

1. Operational amplifier stage OP1 enables a positive voltage signal to be amplified. OP1 gain GGAIN can be set

via external resistors R1 and R2. Protective circuitry against overvoltage is integrated into the chip, limiting

the voltage to the set value of the reference voltage. Output voltage VOUTAD at pin OUTAD is calculated as:

GAIN

INP

OUTAD

G

V

V

⋅

=

with

2

1

1

R

R

G

GAIN

+

=

(1)

where VINP is the voltage at OP1 input pin INP.

2. Using the current-limited operational amplifier stage OP3 with its integrated protection against reverse po-

larity an industrial voltage signal (VOUT) can be realised. The internal amplification of OP3 is set to a fixed

value of GOP = 2.2. The output is configured as a driver so that OP3 is particularly suitable as an output

stage. For OP3 output voltage VOUT at pin VOUT of the IC the following applies:

INDAV

OP

OUT

V

G

V

⋅

=

(2)

with VINDAV the voltage at pin INDAV (OP3 input).

3. The voltage-to-current converter (V/I converter) provides a voltage-controlled current signal at IC output

IOUT (pin 8) which activates an external transistor T1; this in turn supplies the actual output current IOUT. To

V

BG

Ground

V

S

I

OUT

R

1

R

2

R

0

T

1

D

1

R

5

V

OUT

V

INP

V

SET

V

OUTAD

V

CVREF

V

CVSET

R

4

V

BG

4

12

11

10

8

OP1

5

2

AM460

OP2

3

C

1

V

REF

R

3

13

15

Voltage Reference

1

16

9

V

INDAI VINDAV

714

V

I

6

OP3

Figure 2: Block diagram of AM460 with external components (3-wire circuit for current output)