Datasheet RCV420JP, RCV420KP Datasheet (Burr Brown)

®

RCV420

Precision 4mA to 20mA

CURRENT LOOP RECEIVER

RCV420

FEATURES

● COMPLETE 4-20mA TO 0-5V CONVERSION

● INTERNAL SENSE RESISTORS

● PRECISION 10V REFERENCE

● BUILT-IN LEVEL-SHIFTING

±40V COMMON-MODE INPUT RANGE

●

● 0.1% OVERALL CONVERSION ACCURACY

● HIGH NOISE IMMUNITY: 86dB CMR

DESCRIPTION

The RCV420 is a precision current-loop receiver de­signed to convert a 4–20mA input signal into a 0–5V
output signal. As a monolithic circuit, it offers high
reliability at low cost. The circuit consists of a pre­mium grade operational amplifier, an on-chip precision
resistor network, and a precision 10V reference. The
RCV420 features 0.1% overall conversion accuracy,
86dB CMR, and ±40V common-mode input range.

The circuit introduces only a 1.5V drop at full scale,
which is useful in loops containing extra instrument
burdens or in intrinsically safe applications where

APPLICATIONS

● PROCESS CONTROL

● INDUSTRIAL CONTROL

● FACTORY AUTOMATION

● DATA ACQUISITION

● SCADA

● RTUs

● ESD

● MACHINE MONITORING

transmitter compliance voltage is at a premium. The
10V reference provides a precise 10V output with a
typical drift of 5ppm/°C.

The RCV420 is completely self-contained and offers a
highly versatile function. No adjustments are needed
for gain, offset, or CMR. This provides three important
advantages over discrete, board-level designs: 1) lower
initial design cost, 2) lower manufacturing cost, and

3) easy, cost-effective field repair of a precision circuit.

V+ V– Ref In
16 4 12

RCV420

1

–In

2

C

T

+In

3

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: [phone] • Twx: 910-952-1111

Internet: http://www.burr-brown.com/ • FAXLine: [phone] (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]

©

1988 Burr-Brown Corporation PDS-837E Printed in U.S.A. October, 1997

300kΩ

RS

75Ω

R

75Ω

300kΩ



S

99kΩ

1.01kΩ

100kΩ

1

92kΩ

13 5

Rcv

Com

11.5kΩ

+10V

Ref

Ref

Com

15
14
11
10



Rcv f

B

Rcv Out
Ref Out



Ref f

B

Ref Trim

8

Ref Noise Reduction

7

®

RCV420

SPECIFICATIONS

ELECTRICAL

At T = +25°C and VS = ±15V, unless otherwise noted.

RCV420KP, JP
CHARACTERISTICS MIN TYP MAX UNITS
GAIN

Initial 0.3125 V/mA
Error 0.05 0.15 % of span
Error—JP Grade 0.25 % of span

vs Temp 15 ppm/°C

Nonlinearity

OUTPUT

Rated Voltage (I
Rated Current (E
Impedance (Differential) 0.01 Ω
Current Limit (To Common) +49, –13 mA
Capacitive Load 1000 pF

INPUT

Sense Resistance 74.25 75 75.75 Ω
Input Impedance (Common-Mode) 200 kΩ
Common-Mode Voltage ±40 V
CMR

AC 60Hz 80 dB

OFFSET VOLTAGE (RTO)

Initial 1mV

ZERO ERROR

Initial 0.025 0.075 % of span
Initial—JP Grade 0.15 % of span

OUTPUT NOISE VOLTAGE

f

B

f

O

DYNAMIC RESPONSE

Gain Bandwidth 150 kHz
Full Power Bandwidth 30 kHz
Slew Rate 1.5 V/µs
Settling Time (0.01%) 10 µs

VOLTAGE REFERENCE

Initial 9.99 10.01 V
Trim Range

Noise (0.1Hz to 10Hz) 5 µVp-p
Output Current +10, –2 mA

POWER SUPPLY

Rated ±15 V
Voltage Range
Quiescent Current (V

TEMPERATURE RANGE

Specification 0 +70 °C
Operation –25 +85 °C
Storage –40 +85 °C
Thermal Resistance,

NOTES: (1) Nonlinearity is the max peak deviation from best fit straight line. (2) With 0 source impedance on Rcv Com pin. (3) Referred to output with all inputs
grounded including Ref In. (4) With 4mA input signal and Voltage Reference connected (includes V
slightly affects drift. (6) I

(1)

= +10mA, –5mA) 10 12 V

O

= 10V) +10, –5 mA

O

0.0002 0.002 % of span

(Stable Operation)

(2)

vs Temp (DC) (T

A

= T

MIN

to T

)76dB

MAX

(3)

70 80 dB

vs Temp 10 µV/°C
vs Supply (±11.4V to ±18V) 74 90 dB
vs Time 200 µV/mo

(4)

vs Temp 10 ppm of

span/°C

= 0.1Hz to 10Hz 50 µVp-p
= 10kHz 800 nV/√Hz

(5)

±4%
vs Temp 5 ppm/°C
vs Supply (±11.4V to ±18V) 0.0002 %/V
vs Output Current (I
vs Time 15 ppm/kHz

= 0 to +10mA) 0.0002 %/mA

O

(6)

= 0V) 3 4 mA

O

θ

JA

Ref = 5mA, IO Rcv = 2mA.

O

–5, +11.4 ±18 V

80 °C/W

, Gain Error, and Voltage Reference Errors). (5) External trim

OS

®

RCV420

2

PIN CONFIGURATION

Top View DIP

–In

C

+In

V–

Ref Com

NC

Ref Noise Reduction

Ref Trim

1
2

T

3
4
5
6
7
8

16
15
14
13
12
11
10

9

V+
Rcv f

B

Rcv Out
Rcv Com
Ref In
Ref Out
Ref f

B

NC

ORDERING INFORMATION

ABSOLUTE MAXIMUM RATINGS

Supply ...............................................................................................±22V

Input Current, Continuous ................................................................ 40mA

Input Current Momentary, 0.1s ........................... 250mA, 1% Duty Cycle

Common-Mode Input Voltage, Continuous ....................................... ±40V

Lead Temperature (soldering, 10s)............................................... +300°C

Output Short Circuit to Common (Rcv and Ref) ..................... Continuous

NOTE: (1) Stresses above these ratings may cause permanent damage.

(1)

PACKAGE INFORMATION

PRODUCT PACKAGE NUMBER

RCV420KP 16-Pin Plastic DIP 180
RCV420JP 16-Pin Plastic DIP 180

NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.

PACKAGE DRAWING

(1)

PRODUCT GRADE PACKAGE

RCV420KP 0°C to +70°C 16-Pin Plastic DIP
RCV420JP 0°C to +70°C 16-Pin Plastic DIP

PERFORMANCE

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.

3

RCV420

®

TYPICAL PERFORMANCE CURVES

At TA = +25°C, VS = ±15V, unless otherwise noted.

STEP RESPONSE

NO LOAD

POSITIVE COMMON-MODE VOLTAGE RANGE

80

70

60

50

40

Positive Common-Mode Range (V)

30

vs POSITIVE POWER SUPPLY VOLTAGE

TA = +25°C

11

12 13 14 15 16 17 18 19 20

11.4

Positive Power Supply Voltage (V)

TA = –55°C

TA = +125°C

Max Rating = 40V

–VS = –5V to –20V

SMALL SIGNAL RESPONSE

NO LOAD

Negative Common-Mode Range (V)

SMALL SIGNAL RESPONSE

R

= ∞, CL = 1000pF

L

NEGATIVE COMMON-MODE VOLTAGE RANGE

–80

–70

–60

–50

–40

–30

–20

–10

vs NEGATIVE POWER SUPPLY VOLTAGE

TA = +25°C

Max Rating = –40V

–5 –20

–10 –15

Negative Power Supply Voltage (V)

TA = –55°C to +125°C

+VS = +11.4V to +20V

COMMON-MODE REJECTION

100

80

CMR (dB)

60

40

1 10 100 1k 10k 100k

®

vs FREQUENCY

Frequency (Hz)

RCV420

POWER-SUPPLY REJECTION

100

90

80

PSR (dB)

60

40

1 10 100 1k 10k 100k

vs FREQUENCY

V+ V–

Frequency (Hz)

4

THEORY OF OPERATION

Refer to the figure on the first page. For 0 to 5V output with
4–20mA input, the required transimpedance of the circuit is:

V

To achieve the desired output (0V for 4mA and 5V for
20mA), the output of the amplifier must be offset by an
amount:

V

The input current signal is connected to either +In or –In,
depending on the polarity of the signal, and returned to
ground through the center tap, C
matched 75Ω sense resistors, R
tion of common-mode voltage signals on C
ential current-to-voltage conversion. The sense resistors
convert the input current signal into a proportional voltage,
which is amplified by the differential amplifier. The voltage
gain of the amplifier is:

A

The tee network in the feedback path of the amplifier
provides a summing junction used to generate the required
–1.25V offset voltage. The input resistor network provides
high-input impedance and attenuates common-mode input
voltages to levels suitable for the operational amplifier’s
common-mode signal capabilities.

= 5V/16mA = 0.3125V/mA.

OUT/IIN

= –(4mA)(0.3125V/mA) = –1.25V.

OS

. The balanced input—two

T

—provides maximum rejec-

S

T

= 5V/(16mA)(75Ω) = 4.1667V/V.

D

and true differ-

necessary level shifting. If the Ref In pin is not used for level
shifting, then it must be grounded to maintain high CMR.

GAIN AND OFFSET ADJUSTMENT

Figure 2 shows the circuit for adjusting the RCV420 gain.
Increasing the gain of the RCV420 is accomplished by
inserting a small resistor in the feedback path of the ampli­fier. Increasing the gain using this technique results in CMR
degradation, and therefore, gain adjustments should be kept
as small as possible. For example, a 1% increase in gain is
typically realized with a 125Ω resistor, which degrades
CMR by about 6dB.

A decrease in gain can be achieved by placing matched
resistors in parallel with the sense resistors, also shown in
Figure 2. The adjusted gain is given by the following
expression

V

= 0.3125 x RX/(RX + RS).

OUT/IIN

A 1% decrease in gain can be achieved with a 7.5kΩ
resistor. It is important to match the parallel resistance on
each sense resistor to maintain high CMR. The TCR mis­match between the two external resistors will effect gain
error drift and CMR drift.

There are two methods for nulling the RCV420 output offset
voltage. The first method applies to applications using the
internal 10V reference for level shifting. For these applica-

BASIC POWER SUPPLY
AND SIGNAL CONNECTIONS

Figure 1 shows the proper connections for power supply and
signal. Both supplies should be decoupled with 1µF tanta­lum capacitors as close to the amplifier as possible. To avoid
gain and CMR errors introduced by the external circuit,
connect grounds as indicated, being sure to minimize ground
resistance. The input signal should be connected to either
+In or –In, depending on its polarity, and returned to ground
through the center tap, C

. The output of the voltage refer-

T

ence, Ref Out, should be connected to Ref In for the

I

IN

4–20mA

+In 3

C

T

–In 1

2

R

75Ω

S

V+

RCV420

16

1µF1µF

4

V–

75Ω

R

S

–In

C

+In

T

10kΩ

10kΩ

(1)

(1)

1

R

X

2

R

X

3

15

RCV420

NOTE: (1) Typical values. See text.

FIGURE 2. Optional Gain Adjustment.

12 Ref In

13
Rcv Com

+10V

Reference

5
Ref Com

15 Rcv f

14 Rcv Out
11 Ref Out

10 Ref f
8 Ref Trim

7 Ref Noise Reduction

B

B

200Ω

(1)

14

V

(0–5V)

O

R

1

±0.5% Gain

Adjustment

Rcv Out

FIGURE 1. Basic Power Supply and Signal Connections.

®

5

RCV420

tions, the voltage reference output trim procedure can be
used to null offset errors at the output of the RCV420. The
voltage reference trim circuit is discussed under “Voltage
Reference.”

When the voltage reference is not used for level shifting or
when large offset adjustments are required, the circuit in
Figure 3 can be used for offset adjustment. A low impedance
on the Rcv Com pin is required to maintain high CMR.

ZERO ADJUSTMENT

Level shifting the RCV420 output voltage can be achieved
using either the Ref In pin or the Rcv Com pin. The
disadvantage of using the Ref In pin is that there is an 8:1
voltage attenuation from this pin to the output of the RCV420.
Thus, use the Rcv Com pin for large offsets, because the
voltage on this pin is seen directly at the output. Figure 4
shows the circuit used to level-shift the output of the RCV420

–In

1

C

T

2

RCV420

+In

3

12

±150mV adjustment at output.

15

14

5

13

OPA237

V

O

100kΩ

1kΩ

+15V

100kΩ

–15V

FIGURE 3. Optional Output Offset Nulling Using External

Amplifier.

using the Rcv Com pin. It is important to use a low-output
impedance amplifier to maintain high CMR. With this method
of zero adjustment, the Ref In pin must be connected to the
Rcv Com pin.

MAINTAINING COMMON-MODE REJECTION

Two factors are important in maintaining high CMR: (1)
resistor matching and tracking (the internal resistor network
does this) and (2) source impedance. CMR depends on the
accurate matching of several resistor ratios. The high accu­racies needed to maintain the specified CMR and CMR
temperature coefficient are difficult and expensive to reli­ably achieve with discrete components. Any resistance im­balance introduced by external circuitry directly affects
CMR. These imbalances can occur by: mismatching sense
resistors when gain is decreased, adding resistance in the
feedback path when gain is increased, and adding series
resistance on the Rcv Com pin.

The two sense resistors are laser-trimmed to typically match
within 0.01%; therefore, when adding parallel resistance to
decrease gain, take care to match the parallel resistance on
each sense resistor. To maintain high CMR when increasing
the gain of the RCV420, keep the series resistance added to
the feedback network as small as possible. Whether the Rcv
Com pin is grounded or connected to a voltage reference for
level shifting, keep the series resistance on this pin as low as
possible. For example, a resistance of 20Ω on this pin
degrades CMR from 86dB to approximately 80dB. For
applications requiring better than 86dB CMR, the circuit
shown in Figure 5 can be used to adjust CMR.

PROTECTING THE SENSE RESISTOR

The 75Ω sense resistors are designed for a maximum con­tinuous current of 40mA, but can withstand as much as
250mA for up to 0.1s (see absolute maximum ratings).
There are several ways to protect the sense resistor from

Use 10V Ref for +

–In

1

C

T

2

+In

3

12

V

ZERO

±5V adjustment
at output.

RCV420

10

5

13

OPA237

and 10V Ref with INA105 for –.

15

14

11

10kΩ

10kΩ

+10V

V

= (0.3125)(IIN) + V

O

V

O

2

3

50kΩ

INA105

Procedure:

ZERO

5

–10V

6

1

RCV420

13

1k

1kΩ

1. Connect CMV to C

2. Adjust potentiometer for near zero
at the output.

Ω

1kΩ

OPA237

1kΩ

200Ω
CMR
Adjust

.

T

FIGURE 4. Optional Zero Adjust Circuit. FIGURE 5. Optional Circuit for Externally Trimming CMR.

®

RCV420

6

overcurrent conditions exceeding these specifications. Refer
to Figure 6. The simplest and least expensive method is a
resistor as shown in Figure 6a. The value of the resistor is
determined from the expression

R

= VCC/40mA – 75Ω

X

and the full scale voltage drop is

= 20mA x RX.

V

RX

For a system operating off of a 32V supply R
V

= 14.5V. In applications that cannot tolerate such a

RX

= 725Ω and

X

large voltage drop, use circuits 6b or 6c. In circuit 6b a
power JFET and source resistor are used as a current limit.
The 200Ω potentiometer, R

, is adjusted to provide a current

X

limit of approximately 30mA. This circuit introduces a
1– 4V drop at full scale. If only a very small series voltage
drop at full scale can be tolerated, then a 0.032A series 217
fast-acting fuse should be used, as shown in Figure 6c.

For automatic fold-back protection, use the circuit shown in
Figure 15.

V+

V

R

RX

X

4–20mA

V+

R

X

2N3970

200Ω

2
1

= (V+)/40mA – 75Ω

a) R

X

4–20mA

2
1

3

3

RCV420

RCV420

15

V

14

15

14

O

V

O

VOLTAGE REFERENCE

The RCV420 contains a precision 10V reference. Figure 8
shows the circuit for output voltage adjustment. Trimming
the output will change the voltage drift by approximately

0.007ppm/°C per mV of trimmed voltage. Any mismatch in
TCR between the two sides of the potentiometer will also
affect drift, but the effect is divided by approximately 5. The
trim range of the voltage reference using this method is
typically ±400mV. The voltage reference trim can be used to
trim offset errors at the output of the RCV420. There is an
8:1 voltage attenuation from Ref In to Rcv Out, and thus the
trim range at the output of the receiver is typically ±50mV.

The high-frequency noise (to 1MHz) of the voltage refer­ence is typically 1mVp-p. When the voltage reference is
used for level shifting, its noise contribution at the output of
the receiver is typically 125µVp-p due to the 8:1 attenuation
from Ref In to Rcv Out. The reference noise can be reduced
by connecting an external capacitor between the Noise
Reduction pin and ground. For example, 0.1µF capacitor
reduces the high-frequency noise to about 200µVp-p at the
output of the reference and about 25µVp-p at the output of
the receiver.

b) RXset for 30mA current limit at 25°C.

V+

f

1

4–20mA

is 0.032A, Lifflefuse Series 217 fast-acting fuse.

c) f

1

Request Application Bulletin AB-014 for details of a
more complete protection circuit.

3
2
1

15

RCV420

FIGURE 6. Protecting the Sense Resistors.

–In

C

+In

1

15

2

T

RCV420

3

10

8

20kΩ

14

11

V

14

O

V

O

V

REF

±400mV adjustment at output of reference, and ±50mV
adjustment at output of receiver if reference is used for
level shifting.

FIGURE 7. Optional V oltage Reference External Trim Circuit.

7

RCV420

®

Pt100

100°C to

600°C

RTD

R

LIN1

5760Ω

R

137Ω

12

1

V

LIN

14

13

R

G

402Ω

Z

I

R1

I

R2

XTR105

11

V

REG

10

V+

9EB

8

I

O

7

IO = 4mA – 20mA

+

V

IN

4

R

G

3

R

G

–

V

2

IN

I

RET

6

1N4148

+12V

1µF

0.01µFQ

1

16

10

11

3

RCV420

2

5

4

1µF

–12V

RCM = 1kΩ

NOTE: A two-wire RTD connection is shown. For remotely

0.01µF

located RTDs, a three-wire RTD conection is recommended.

becomes 383Ω, R

R

G

Table I.

is 8060Ω. See Figure 3 and

LIN2

FIGURE 8. RCV420 Used in Conjunction with XTR101 to Form a Complete Solution for 4-20mA Loop.

12

VO = 0 to 5V

15

14

13



12

1

V

LIN

14

I

R1

+

V

IN

4

R

G

3

R

G

–

V

2

IN

I

RET

6

11

I

R2

10

V

REG

V+

9

B

XTR105

NOTE: A three-wire RTD connection is shown.
For a two-wire RTD connection eliminate R

E

8

I

O

7

IO = 4mA – 20mA

1

RTD

R

Z

R

LIN2

RCM = 1kΩ

0.01µF

13

R

G

R

LIN1

FIGURE 9. Isolated 4-20mA Instrument Loop (RTD shown).

1N4148

0.01µFQ

LIN2

+15V

1µF

1µF

16

10

11

3

12

RCV420

2

4

.

15

14

13

5

15

ISO122

16

0

–15V

1

10

2

Isolated Power
from PWS740

V+

9

7

V

8

0 – 5V

V–

O

®

RCV420

8

4–20mA

+In

C

–In

T

10

R

R

S

S

11

RCV420

(1)

12

15

14

V

O

(0–5V)

13

3

2

1

5

10

(1)

R

G

15

14

V

O

(0–5V)

R

R

S

S

11

12

RCV420

(N)

13

5

+In

3

C

T

2

–In

1

(1)

R

CM

NOTE: (1) R
and Gain Error, respectively. Table 1 gives typical resistor values for R

and RG are used to provide a first order correction of CMR

CM

and RG when as many as three RCV420s are stacked. Table II gives
typical CMR and Gain Error with no correction. Further improvement in
CMR and Gain Error can be achieved using a 500kΩ potentiometer for
R

and a 100Ω potentiometer for RG.

CM

RCV420 RCM (kΩ)R

1

∞ 0

(Ω)

G

2 200 7
367 23

TABLE 1. Typical Values for RCM and RG.

RCV420 CMR (dB) GAIN ERROR %

1 94 0.025
2 68 0.075
3 62 0.200

TABLE II. Typical CMR and Gain Error

Without Correction.

FIGURE 10. Series 4-20mA Receivers.

I

1

+In

3

RCV420

12

15

14

13

R

C

T

I

2

–In

S

2

R

S

1

5

3

15

14

11

V

O

(5–0V)

10

+10V

12kΩ

4–20mA

2

C

RCV420

T

1

5

13

12

+6.25V

+6.25V

OPA237

20kΩ

VO = 6.25V – (0.3125) (IIN)

FIGURE 12. 4-20mA to 5-0V Conversion.

I

L

Load

CM

R

(1)

X

Power 

+In

C

+In

3

RCV420

12

15

14

13

V

O

(0-5V)



R

T

(1)

R

X

S

2

R

S

1

5

Supply

–40V (max)

+40V (max)

Power

Supply

+In

RCV420

12

15

14

13

(

IL

MAX

16mA

VO

(0-5V)

–1

)

(1)

R

C

T

(1)

R

X

–In

Load

I

L

R

X

S

R

S

5

NOTE: (1) RX = RS/

FIGURE 13. Power Supply Current Monitor Circuit.

V

O

VO = 0.3125 (I1 – I2)
Max Gain Error = 0.1% (RCV420BG)

FIGURE 11. Differential Current-to-Voltage Converter.

®

9

RCV420

AT&T

LH1191

Solid-State

Relay

16 4

1

2

3

+5V

1MΩ

300kΩ 99kΩ

75Ω

75Ω

300kΩ

8

7

555

6

Timer

1µF 0.01µF

3

–15V+15V

4

2
5

1

RCV420

1.01kΩ

100kΩ

13 5

10kΩ 10kΩ

92kΩ

11.5kΩ

10.0V

Reference

LM193

12
15
14

10.0V

10
11

+15V

8

10kΩ

1.27kΩ

10kΩ

10kΩ

6.95V

V

OUT

0–5V

4–20mA

Input

See Application Bulletin AB-014 for more details.

470Ω 47kΩ

1µF

Overrange

Output

2N3904

Underrange

Output

FIGURE 14. 4-20mA Current Loop Receiver with Input Overload Protection.

+15V –15V

16 4

300kΩ

RCV420

1.01kΩ

100kΩ

301Ω

0-20mA

Input

301Ω

See Application Bulletin AB-018 for more details.

1

75Ω

2

75Ω

3

0.57V

0-5V

V

22.9kΩ

O

4

92kΩ99kΩ300kΩ

11.5kΩ

10.0V
Ref

13

5

604Ω

12

15
14

10

11

FIGURE 15. 0-20mA/0-5V Receiver Using RCV420.

®

RCV420

10