Texas Instruments Single Supply 4-20mA Current Loop Receiver Application notes

Brand: Texas Instruments

Model: Single Supply 4-20mA Current Loop Receiver

Type: Application notes

Texas Instruments Single Supply 4-20mA Current Loop Receiver is a device that enables the user to convert a 4-20mA current loop signal to a 0-5V output voltage. This device can operate on a single supply ranging from +15V to +36V (+44V absolute max). The pseudo ground (Ref Out) can source or sink up to 5mA. Some of its key advantages include:

No external components required
Current loop can be sourcing or sinking
Current loop can be referenced to either the power-supply V+ or ground
Complete circuit for a single-supply current loop receiver is included in the product documentation
Isolated single-supply 4-20mA current loop receiver can be connected to an isolation amplifier

No external components required
Current loop can be sourcing or sinking
Current loop can be referenced to either the power-supply V+ or ground
Complete circuit for a single-supply current loop receiver is included in the product documentation
Isolated single-supply 4-20mA current loop receiver can be connected to an isolation amplifier

99kΩ

RCV420

92kΩ300kΩ

75Ω

300kΩ

1.01kΩ

11.5kΩ

10.0V

Ref

0 to 5V

Meter

10.0V to

5.0V

10.0V 

Pseudo

Ground

Ref

Rcv

Ref

Out

Ref

Out

Ref

Com

Rcv

Com

V–

100kΩ

(1)

+In

–In

V+

+28V

(15V to 36V)

4-20mA

Input from

Current Loop

NOTE: (1) NC = No Connection.

FIGURE 1.

Many industrial current-loop data acquisition systems oper-

ate on a 24V or 28V single supply. You can make a single-

supply current loop receiver with the RCV420 by using its

10V reference as a pseudo ground. The RCV420 will con-

vert a 4-20mA loop current into a 0 to 5V output voltage

with no external components required. The current loop can

be sourcing or sinking and can be referenced to either the

power-supply V+ or ground.

The complete circuit for a single-supply current loop re-

ceiver is shown in Figure 1. In this application, a 4-20mA

current source referenced to power-supply ground drives the

receiver. The V– terminal and the Ref Com terminal of the

RCV420 are both tied to power supply ground. The 10V

reference output (Ref Out) becomes a pseudo ground where

the current loop receiver common pin (Rcv Com) is tied. The

current loop receiver output is now referenced to the 10V

pseudo ground.

In normal operation, the 4-20mA current loop signal would

produce a 0-5V output with the RCV420 offset pin (Ref In)

connected to the +10V reference. The 10V reference pro-

vides a –1.25V offset so 4mA input current will produce 0V

out. In this application, the Ref In pin is connected to power

supply ground which acts as a –10V reference—producing

a +1.25V offset. Now with the inputs connected for an

inverted output signal, the RCV420 output will be 0 to –5V

referenced to the pseudo ground. Since the pseudo ground is

at 10V, the actual output will be 10V to 5V—a signal which

can drive most floating ground meters.

For a current loop receiver with a 4-20mA current sink

referenced to the power-supply V+, use the connection

shown in Figure 2.

The circuit can operate on a single supply ranging from

+15V to +36V (+44V absolute max). The pseudo ground

(Ref Out) can source or sink up to 5mA.

For an isolated single-supply 4-20mA current loop receiver,

you can connect the circuit to an isolation amplifier as

shown in Figure 3. In this circuit the ISO122 is operated

single-supply using the 10.0V pseudo ground. Note that the

output side of the isolation amplifier still requires dual

supplies.

Output from the ISO122 will be 0 to –5V. You could

interchange the input connections to the ISO122 to get a 0

to 5V output, but power-supply rejection would degrade

performance.

The ISO122 is a low-cost iso amp in a standard plastic DIP.

For a hermetic isolation amplifier, use the ISO120. Hook-up

details are shown in Application Bulletin AB-009.

SINGLE SUPPLY 4-20mA CURRENT LOOP RECEIVER

By R. Mark Stitt and David Kunst (602) 746-7445

APPLICATION BULLETIN

Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706

Tel: (602) 746-1111 • Twx: 910-952-111 • Telex: 066-6491 • FAX (602) 889-1510 • Immediate Product Info: (800) 548-6132

1992 Burr-Brown Corporation AB-041 Printed in U.S.A. June, 1992

SBOA023

FIGURE 2.

FIGURE 3.

99kΩ

RCV420

92kΩ300kΩ

75Ω

300kΩ

1.01kΩ

11.5kΩ

10.0V

Ref

0 to 5V

Meter

10.0V to

5.0V

10.0V 

Pseudo

Ground

Ref

Rcv

Ref

Out

Ref

Out

Ref

Com

Rcv

Com

V–

100kΩ

(1)

+In

–In

V+

+28V

(15V to 36V)

4-20mA

Input from

Current Loop

NOTE: (1) NC = No Connection.

99kΩ

RCV420

92kΩ300kΩ

75Ω

300kΩ

1.01kΩ

11.5kΩ

10.0V

Ref

Ref

Rcv

Ref

Out

Ref

Out

Ref

Com

Rcv

Com

V–

100kΩ

(1)

+In

–In

V+

+28V

(15V to 36V)

4-20mA

Input from

Current Loop

NOTE: (1) NC = No Connection.

Gnd

ISO

122

Com 2

–V



(–15V)



(+15V)

= 0 to –5V

–V



The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN

assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject

to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not

authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.

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Texas Instruments Single Supply 4-20mA Current Loop Receiver Application notes

Brand: Texas Instruments

Model: Single Supply 4-20mA Current Loop Receiver

Type: Application notes

No external components required
Current loop can be sourcing or sinking
Current loop can be referenced to either the power-supply V+ or ground
Complete circuit for a single-supply current loop receiver is included in the product documentation
Isolated single-supply 4-20mA current loop receiver can be connected to an isolation amplifier

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Texas Instruments Single Supply 4-20mA Current Loop Receiver Application notes

Texas Instruments Single Supply 4-20mA Current Loop Receiver Application notes

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