Datasheet

ManualsBrandsAnalog Microelectronics ManualsData & Signal ConvertersU/I converter IC SO-8

VOLTAGE/CURRENT CONVERTER AM422

analog microelectronics

April 99

Analog Microelectronics GmbH Phone: +49 (0)6131/91 073 – 0 1/10

An der Fahrt 13, D – 55124 Mainz Fax: +49 (0)6131/91 073 – 30 Rev. 2.1

Internet: www.analogmicro.de E–Mail: info@analogmicro.de

FEATURES

• Wide Supply Voltage Range: 6...35V

• Wide Operating Temperature Range:

–40°C...+85°C

• Adjustable Voltage Reference:

4.5 to 10V

• Operational Amplifier Input:

0.5...4.5V, 0...5V, other

• Adjustable Offset Current

• Available as Three– (0/4...20mA) or

Two–Wire Version (4...20mA)

• Adjustable Output Current Range

• Protection Against Reverse Polarity

• Protected Current Output

APPLICATIONS

• Sensor Interface

• Industrial Process Control

• Programmable Current Source

• Current Source Reference

GENERAL DESCRIPTION

The AM422 is a low cost monolithic voltage–

to–current converter specially designed for

analog signal transmission. The AM422 is

available in a 3– or 2–wire version, which al-

lows applications with flexible input voltage

ranges to be used for a standard output current.

Output current range and current offset level

are freely adjustable by external resistors. The

IC consists of three basic sections: an opera-

tional amplifier input stage for single ended

input signals (0.5–4.5V, 0–10V, or other), a

programmable 4.5 to 10V reference for trans-

ducer excitation, and a current output, freely

adjustable in a wide current range (4–20mA,

0–20mA, other). With the broad spectrum of

possible input signals the AM422 is a flexible

and multipurpose voltage–to–current converter

for single ended transducers or voltage trans-

mission.

DELIVERY

• DIL8 packages (samples)

• SOP8 packages

• Dice on 5“ blue foil

BLOCK DIAGRAM

VIN

OUT

SET

VCC

GND

AM422

Input

Amplifier

G = 1

REF

VREF

VSET

Reference Voltage

Figure 1

Summary of content (10 pages)

PAGE 1
VOLTAGE/CURRENT CONVERTER AM422 FEATURES GENERAL DESCRIPTION • Wide Supply Voltage Range: 6...35V • Wide Operating Temperature Range: –40°C...+85°C • Adjustable Voltage Reference: 4.5 to 10V • Operational Amplifier Input: 0.5...4.5V, 0...5V, other • Adjustable Offset Current • Available as Three– (0/4...20mA) or Two–Wire Version (4...
PAGE 2
VOLTAGE/CURRENT CONVERTER AM422 ELECTRICAL SPECIFICATIONS Tamb = 25°C, VCC = 24V, VREF = 5V, IREF = 1mA (unless otherwise noted) Parameter Symbol Voltage Range VCC Quiescent Current ICC Conditions Min. Typ. 6 Tamb = – 40...+85°C, IREF = 0mA Max. Unit 35 V 1.5 mA 85 °C Temperature Specifications Operating Tamb –40 Storage Tst –55 Junction TJ Thermal Resistance Θja DIL8 plastic package 110 °C/W Θja SO8 plastic package 180 °C/W VREF VSET not connected 4.75 5.00 5.
PAGE 3
VOLTAGE/CURRENT CONVERTER Parameter Symbol Conditions Min. AM422 Typ. Max. Unit V/I Converter Internal Gain GVI 1.00 Trim Range adjustable by R0 0.75 1.00 1.25 400 Voltage Range at R0 FS VR0FS 500 580 mV Offset Voltage VOS β F ≥ 100 ±2 ±6 mV VOS vs. Temperature dVOS/dT β F ≥ 100 ±7 ±20 µV/°C Output Offset Current IOUTOS 3–wire operation –35 –50 µA IOUTOS vs.
PAGE 4
VOLTAGE/CURRENT CONVERTER AM422 FUNCTIONAL DIAGRAMS Voltage Reference 3−Wire System VS RA Input Amplifier V IOUT VIN RIN I RL Ground Figure 2 Voltage Reference 2−Wire System VS RA Input Amplifier VIN RIN V IOUT I RL Ground Figure 3 FUNCTIONAL DESCRIPTION The IC AM422 is an integrated voltage–to–current converter for a broad spectrum of possible single ended input signals. With variations of a few external components the output current can be adjusted over a wide range.
PAGE 5
VOLTAGE/CURRENT CONVERTER AM422 has to be connected between the resistors R5 and RL. In this case the IC supply voltage VCC depends on the voltage VS and the load resistor RL and can be calculated: VCC = VS − IOUT ⋅ RL (1) Basically the IC AM422 is composed of 3 functional sections as they shown in Figure 1: 1. An operational amplifier input which allows the adjustment of the output current range with the two external resistors R1 and R2.
PAGE 6
VOLTAGE/CURRENT CONVERTER AM422 the input voltage VIN has to change to  R2  ∆V PIN 4 = ∆VIN    R1 + R2  (8) With the value of the relationship of the resistors R1 and R2 R1 ∆VIN − ∆V PIN 4 = R2 ∆V PIN 4 (9) the additional offset current can be calculated as I SET = I OUTmin − I INmin = I OUTmin − VINmin  R2    2 R0  R1 + R2  (10) The value of the set resistor can then be found using equation 4 In respect to the load resistor RL, the value of the supply voltage VS has to be considered wi
PAGE 7
VOLTAGE/CURRENT CONVERTER AM422 PINOUT PIN VCC 1 8 VREF RS 2 7 GND OUT 3 6 VSET VIN 4 5 SET Figure 5 NAME DESIGNATION 1 VCC Supply Voltage 2 RS Sense Resistor 3 OUT Output 4 VIN Voltage Input 5 SET Set Voltage 6 VSET Reference Voltage Select 7 GND IC Ground 8 VREF Reference Voltage Output DELIVERY The AM422 is available in 2– (AM422–2) or 3–wire version (AM422–1). The different versions are pin compatible.
PAGE 8
VOLTAGE/CURRENT CONVERTER AM422 TYPICAL THREE–WIRE APPLICATION (0 – 5/10V) R3 VREF 6 RSET C1 8 AM422−1 VS 5 VSET R4 VREF 2 G=1 VOFFSET 5/10 V Reference 1 R0 2 V VIN Amplifier 4 I R1 7 R2 3 T1 D1 IOUT R5 RL Ground Figure 7 Used in a three–wire circuit (AM422–1) ground pin 7 (GND) is connected to Ground (Figure 7).
PAGE 9
VOLTAGE/CURRENT CONVERTER AM422 TYPICAL THREE–WIRE APPLICATION (0.5 – 4.5V) C1 VREF R3 6 RSET 5 VSET R4 Sensor 0.5−4.5V 8 AM422−1 VREF 2 G=1 VOFFSET VS 5/10 V Reference 1 R0 V 2 VIN 4 Amplifier I R1 3 7 R2 T1 D1 IOUT R5 RL Ground Figure 8 Example 3: Output current range IOUT = 4...20mA, input voltage range VIN = 0.5...4.5V The transfer function of the output current IOUT is (equation 2) V  R2  I OUT = I SET + I IN = I SET + IN   2 R0  R1 + R2  For the 0.5 to 4.
PAGE 10
VOLTAGE/CURRENT CONVERTER AM422 TYPICAL TWO–WIRE APPLICATION (0 – 1V) R3 VREF 6 RSET C1 8 AM422−2 VS 5 VSET R4 VREF 2 G=1 VOFFSET 5/10 V Reference 1 C2 R0 2 V VIN Amplifier 4 I R1 7 R2 3 T1 D1 IOUT R5 RL Ground Figure 9 Used in a two–wire circuit (AM422–2) ground pin 7 (GND, ⊥) is connected between R5 and the load resistor (Figure 9).