Industrial Converter and Protector IC
V
REF
V
CVREF
1
V
CVSET
2
13
C
1
15
AM460
R
3
16
R
4
V
SET
V
S
AM460
I
OP2
V
BG
Voltage Reference
11
10
9
R
0
V
INP
3
V
OP1
4
R
1
R
2
V
OUTAD
5
6
7
8
T
1
D
1
V
OUT
OP3
14
12
R
5
I
OUT
V
INDAI
V
INDAV
Ground
Figure 2:
Block diagram of AM460 with external components (3-wire circuit for current output)
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:
V
OUTAD
=
V
INP
⋅
G
GAIN
with
G
GAIN
=
1
+
R
1
R
2
(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:
V
OUT
=
G
OP
⋅
V
INDAV
(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
analog microelectronics
April 2003
7/18
AME [ ANALOG MICROELECTRONICS ]
