AM452 – Voltage-to-current transducer IC
with a differential input
PRINCIPLE FUNCTION
Amplification and conversion of differential input voltages (±400mV with a CMIR
of 1.5 – V
CC
-3V) into an adjustable current output of 0/4...20mA, for example. The
offset and maximum output currents are independently adjustable in a wide range.
The IC is suitable for both 2- and 3-wire applications and as a HART
®
carrier IC.
V
CC
= 6…35V
Differential input
±
400
mV
AM452
I
OUT
= z.B.0/4...20mA
V
REF
= 5/10V
I
S
= max 10mA
TYPICAL APPLICATIONS
Transducers for differential input signals in current output values for:
•
•
•
•
•
Transducers for sensor applications with an internal sensing element supply
Drivers for the analog industrial power grid (e.g. remote display in current loop operation)
Differential impedance converters
Carrier for standard HART
®
protocol communications
Modular signal conditioning with digital correction (Frame concept [1])
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: info@analogmicro.de
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
February 2008 - Rev 1.2 - Page 1/21
AM452 – Voltage-to-current transducer IC
with a differential input
TABLE OF CONTENTS
PRINCIPLE FUNCTION
FEATURES
SCHEMATIC
GENERAL DESCRIPTION
ELECTRICAL SPECIFICATIONS
BOUNDARY CONDITIONS
DETAILED DESCRIPTION OF FUNCTIONS
Instrumentation amplifier (IA)
Operational amplifier stage (OP1)
Zero adjust stage
SET stage
Voltage-to-current converter (V/I converter)
Reference voltage source
Additional operational amplifier OP2
OPERATING AM452
2- and 3-wire applications in general [2]
Differences in the AM452 circuitry with 2- and 3-wire applications
Selecting the supply voltage
Setting the offset and output current range for
V
IN
= 0
OPERATING AM452: IMPORTANT POINTS TO NOTE
DIMENSIONING
APPLICATIONS
Typical 3-wire application with a differential input signal
Typical 2-wire application with a differential input signal
Offset compensation using a voltage divider at SET stage
Using OP2 as a current source
Using OP2 as a voltage source
BLOCK DIAGRAM AND PINOUT
DELIVERY
PACKAGE DIMENSIONS
FURTHER READING
NOTES
1
3
3
3
4
7
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: info@analogmicro.de
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
February 2008 - Rev 1.2 - Page 2/21
AM452 – Voltage-to-current transducer IC
with a differential input
FEATURES
•
Instrumentation amplifier input with a
wide voltage range of ±400mV
•
Adjustable gain and offset
•
Adjustable current output
(e.g. of 0/4...20mA)
•
2- and 3-wire operation
•
Suitable for HART
®
applications
•
Protection against reverse polarity and
short-circuiting
•
Output signal limiting
•
Integrated current source
•
Adjustable integrated reference voltage
source of 5 to 10V
•
Modular configuration
•
Supply voltage of 6...35V
•
Temperature range of -40°C...+85°C
•
RoHS compliant
GENERAL DESCRIPTION
AM452 is an integrated transducer with an
adjustable current output which has been
specifically designed for the conditioning of
differential input signals. It permits the
independent adjustment of the offset and full-
scale current using just a few components.
The IC consists of various functional modules. In
addition to the instrumentation amplifier in the
signal path there is an operational amplifier which
is used to set the gain. The offset can be adjusted
using the Zero adjust stage and/or the SET stage
module.
An additional operational amplifier can supply
external components. The adjustable current
output stage permits 2- and 3-wire operation by
way of a simple amendment to the circuitry.
The IC is distinguished by its many protective
functions which include protection against
reverse polarity and short-circuiting and also an
internal current limit.
SCHEMATIC
Prog. Reference
Reference Offset
OP2 Output
1
12
15
16
OP2
Input
Differential
input
voltages
2
V
BG
3
4
SET Stage
11
10
OP2
Voltage Reference
V/I Converter
VCC
Output
9
8
IA
ZERO Stage
13
5
OP1
AM452
7
14
Offset
Amplifier
GND
Figure 1:
Block diagram of AM452
Figure 1:
Schematic of AM452
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: info@analogmicro.de
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
February 2008 - Rev 1.2 - Page 3/21
AM452 – Voltage-to-current transducer IC
with a differential input
ELECTRICAL SPECIFICATIONS
T
amb
= 25°C,
V
CC
= 24V,
V
REF
= 5V,
I
REF
= 1mA (unless otherwise stated)
Parameter
Supply Voltage Range
Quiescent Current
Temperature Specifications
Operating
Storage
Junction
Voltage Reference
Voltage
Current
V
REF
vs. Temperature
Line Regulation
Load Regulation
Load Capacitance
Current/Voltage Source OP2
Internal Reference
V
BG
vs. Temperature
Current Source:
I
CV
=
V
BG
/R
EXT
Adjustable Current Range*
Output Voltage
I
CV
*
V
CV
V
CV
Voltage Source:
V
CV
=
V
BG
(R
EXT1
+
R
EXT2
) /
R
EXT2
Adjustable Voltage Range
Output Current
Load Capacitance
V
CV
V
CV
I
CV
*
I
CV
C
L
V
CC
< 19V
V
CC
≥
19V
Source
Sink
Source mode
0
1
0.4
0.4
V
CC
– 4
15
10
–100
10
V
V
mA
µA
nF
V
CC
< 19V
V
CC
≥
19V
0
V
BG
V
BG
10
V
CC
– 4
15
mA
V
V
V
BG
dV
BG
/dT
T
amb
= - 40...+85°C
1.20
1.27
±60
1.35
±140
V
ppm/°C
V
REF
V
REF
I
REF
*
dV
REF
/dT
dV
REF
/dV
dV
REF
/dV
dV
REF
/dI
dV
REF
/dI
C
L
I
REF
≈
5mA
1.9
T
amb
= - 40...+85°C
V
CC
= 6V...35V
V
CC
= 6V...35V,
I
REF
≈
5mA
VSET
not connected
VSET
=
GND, V
CC
≥
11V
4.75
9.5
0
±90
30
60
0.05
0.06
2.2
5.00
10.0
5.25
10.5
10.0
±140
80
150
0.10
0.15
5.0
V
V
mA
ppm/°C
ppm/V
ppm/V
%/mA
%/mA
µF
T
amb
T
st
T
J
–40
–55
85
125
150
°C
°C
°C
Symbol
V
CC
I
CC
Conditions
VSET
not connected
T
amb
= – 40...+85°C,
I
REF
= 0mA
Min.
6
Typ.
Max.
35
1.5
Unit
V
mA
* In 2-wire operation
I
S
has to fulfill the condition
I
CC
+I
S
<
I
OUTmin
with
I
OUTmin
= 4mA
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: info@analogmicro.de
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
February 2008 - Rev 1.2 - Page 4/21
AM452 – Voltage-to-current transducer IC
with a differential input
Parameter
Instrumentation Amplifier (cont.)
Internal Gain
Differential Input Voltage Range
Common Mode Input Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Offset Voltage
V
OS
vs. Temperature
Input Bias Current
I
B
vs. Temperature
Output Voltage
Minimum Output Voltage
Load Capacitance
Zero Adjust Stage
Internal Gain
Zero Adjust Voltage
G
ZA
V
ZA
V
ZA
≤
V
OUTIAmax
–
G
IA
∆V
IN
; Vcc<9V,
∆V
IN
=400mV, G
IA=
5
V
ZA
≤
V
OUTIAmax
–
G
IA
∆V
IN
; Vcc≥9V,
∆V
IN
=400mV, G
IA=
5
Offset Voltage
V
OS
vs. Temperature
Input Bias Current
I
B
vs. Temperature
Adjustable Gain
Input Range
Power Supply Rejection Ratio
Offset Voltage
V
OS
vs. Temperature
Input Bias Current
I
B
vs. Temperature
Output Voltage Limitation
Output Voltage Range
Load Capacitance
V
OS
dV
OS
/dT
I
B
dI
B
/dT
G
GAIN
IR
IR
PSRR
V
OS
dV
OS
/dT
I
B
dI
B
/dT
V
LIM
V
OP
V
OP
C
L
V
CC
< 10V
V
CC
≥
10V
0
0
V
CC
< 10V
V
CC
≥
10V
1
0
0
80
-3.0
90
-1.0
±3
10
7
V
REF
V
CC
– 5
V
REF
250
1.0
±7
25
20
V
CC
– 5
5
V
V
dB
mV
µV/°C
nA
pA/°C
V
V
V
pF
0.94
0
0
±0.5
±1.6
47
18
1
1.06
Vcc-6
3
±2.0
±5
120
30
V
V
mV
µV/°C
nA
pA/°C
G
IA
V
IN
CMIR
CMIR
CMRR
PSRR
V
OS
dV
OS
/dT
I
B
dI
B
/dT
V
OUTIA
V
OUTIA
V
OUTIAmin
C
L
V
CC
< 9V
V
CC
≥
9V
4.5
V
CC
< 9V,
I
CV
< 2mA
V
CC
≥
9V,
I
CV
< 2mA
4.9
0
1.5
1.5
80
80
-9.0
90
90
-1.5
±5
–100
–0.4
–250
–0.9
V
CC
– 4
5
16
250
+6.0
5
5.1
±400
V
CC
– 3
6.0
mV
V
V
dB
dB
mV
µV/°C
nA
nA/°C
V
V
mV
pF
Symbol
Conditions
Min.
Typ.
Max.
Unit
Operational Amplifier – Gain Stage (OP1)
NB: The current in the IC is given as a negative quantity.
Phone: +49 (0)6131/91 073-0
Fax:
+49 (0)6131/91 073-30
Internet:
http://www.analogmicro.de
Email: info@analogmicro.de
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
February 2008 - Rev 1.2 - Page 5/21
分立器件
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