Datasheet

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 G
GAIN
can be set
via external resistors R
1
and R
2
. Protective circuitry against overvoltage is integrated into the chip, limiting
the voltage to the set value of the reference voltage. Output voltage V
OUTAD
at pin OUTAD is calculated as:
GAININPOUTAD
GVV
⋅=
with
2
1
1
R
R
G
GAIN
+= (1)
where V
INP
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 (V
OUT
) can be realised. The internal amplification of OP3 is set to a fixed
value of G
OP
= 2.2. The output is configured as a driver so that OP3 is particularly suitable as an output
stage. For OP3 output voltage V
OUT
at pin VOUT of the IC the following applies:
INDAVOPOUT
VGV
⋅=
(2)
with V
INDAV
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 T
1
; this in turn supplies the actual output current I
OUT
. 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
V
INDAV
714
V
I
6
OP3
Figure 2: Block diagram of AM460 with external components (3-wire circuit for current output)