Precision Lowest CostISOLATION AMPLIFIER

FEATURES 100% TESTED FOR HIGH-VOLTAGE

BREAKDOWN

RATED 1500Vrms

HIGH IMR: 140dB at 60Hz

BIPOLAR OPERATION: V O = ±10V

16-PIN PLASTIC DIP AND 28-LEAD SOIC

EASE OF USE: Fixed Unity GainConfiguration

0.020% max NONLINEARITY

±4.5V to ±18V SUPPLY RANGE

APPLICATIONS INDUSTRIAL PROCESS CONTROL:

Transducer Isolator, Isolator for Thermo-couples, RTDs, Pressure Bridges, andFlow Meters, 4mA to 20mA Loop Isolation

GROUND LOOP ELIMINATION

MOTOR AND SCR CONTROL

POWER MONITORING

PC-BASED DATA ACQUISITION

TEST EQUIPMENT

VOUT

VIN

+VS1

ISO122

DESCRIPTIONThe ISO122 is a precision isolation amplifier incor-porating a novel duty cycle modulation-demodulationtechnique. The signal is transmitted digitally acrossa 2pF differential capacitive barrier. With digital modu-lation the barrier characteristics do not affect signalintegrity, resulting in excellent reliability and good highfrequency transient immunity across the barrier. Bothbarrier capacitors are imbedded in the plastic body ofthe package.

The ISO122 is easy to use. No external componentsare required for operation. The key specifications are0.020% max nonlinearity, 50kHz signal bandwidth,and 200µV/°C VOS drift. A power supply range of±4.5V to ±18V and quiescent currents of ±5.0mA onV

S1 and ±5.5mA on V

S2 make these amplifiers ideal

for a wide range of applications.

The ISO122 is available in 16-pin plastic DIP and 28-lead plastic surface mount packages.

–VS1

Gnd

+VS2

–VS2

Gnd

©1989 Burr-Brown Corporation PDS-857F Printed in U.S.A. November, 1993

International Airport Industrial Park • Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132

SBOS160

2

®

ISO122

The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumesno 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 changewithout 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 warrantany BURR-BROWN product for use in life support devices and/or systems.

SPECIFICATIONSAt TA = +25°C , VS1 = VS2 = ±15V, and RL = 2kΩ unless otherwise noted.

ISO122P/U ISO122JP/JU

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

ISOLATIONVoltage Rated Continuous AC 60Hz 1500 * VAC100% Test (1) 1s, 5pc PD 2400 * VACIsolation Mode Rejection 60Hz 140 * dBBarrier Impedance 1014 || 2 * Ω || pFLeakage Current at 60Hz VISO = 240Vrms 0.18 0.5 * * µArms

GAIN VO = ±10V

Nominal Gain 1 * V/V Gain Error ±0.05 ±0.50 * * %FSR Gain vs Temperature ±10 * ppm/°C Nonlinearity(2) ±0.016 ±0.020 ±0.025 ±0.050 %FSR

INPUT OFFSET VOLTAGEInitial Offset ±20 ±50 * * mV vs Temperature ±200 * µV/°C vs Supply ±2 * mV/VNoise 4 * µV/√Hz

INPUTVoltage Range ±10 ±12.5 * * VResistance 200 * kΩ

OUTPUTVoltage Range ±10 ±12.5 * * VCurrent Drive ±5 ±15 * * mACapacitive Load Drive 0.1 * µFRipple Voltage(3) 20 * mVp-p

FREQUENCY RESPONSESmall Signal Bandwidth 50 * kHzSlew Rate 2 * V/µsSettling Time VO = ±10V 0.1% 50 * µs 0.01% 350 * µsOverload Recover Time 150 * µs

POWER SUPPLIESRated Voltage ±15 * VVoltage Range ±4.5 ±18 * * VQuiescent Current: VS1 ±5.0 ±7.0 * * mA V

S2±5.5 ±7.0 * * mA

TEMPERATURE RANGESpecification –25 +85 * * °COperating –25 +85 * * °CStorage –40 +85 * * °Cθ

JA100 * °C/W

θJC 65 * °C/W

* Specification same as ISO122P/U.NOTES: (1) Tested at 1.6 X rated, fail on 5pC partial discharge. (2) Nonlinearity is the peak deviation of the output voltage from the best-fit straight line. It is expressedas the ratio of deviation to FSR. (3) Ripple frequency is at carrier frequency (500kHz).

3

®

ISO122

Top View —P Package

1

2

7

8

16

15

9

Gnd

VIN

VOUT

–VS1

+VS1

10

+VS2Gnd

–VS2

Top View—U Package

1

2

28

27

Gnd

VIN

VOUT

–VS1

+VS1

+VS2Gnd

–VS216

15

13

14

CONNECTION DIAGRAM

ABSOLUTE MAXIMUM RATINGS

Supply Voltage ................................................................................... ±18VV

IN ......................................................................................................±100V

Continuous Isolation Voltage ..................................................... 1500VrmsJunction Temperature .................................................................... +150°CStorage Temperature ....................................................................... +85°CLead Temperature (soldering, 10s) ................................................ +300°COutput Short to Common ......................................................... Continuous

PACKAGE INFORMATION (1)

PACKAGE DRAWINGMODEL PACKAGE NUMBER

ISO122P 16-Pin Plastic DIP 238ISO122JP 16-Pin Plastic DIP 238ISO122U 28-Pin Plastic SOIC 217-1ISO122JU 28-Pin Plastic SOIC 217-1

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

NONLINEARITYMODEL PACKAGE MAX %FSR

ISO122P Plastic DIP ±0.020ISO122JP Plastic DIP ±0.050ISO122U Plastic SOIC ±0.020ISO122JU Plastic SOIC ±0.050

ORDERING INFORMATION

4

®

ISO122

+10

0

–10

0

Out

put V

olta

ge (

V)

500

Time (µs)

SINE RESPONSE(f = 2kHz)

1000

Time (µs)

+10

0

–10

0

Out

put V

olta

ge (

V)

10050

SINE RESPONSE(f = 20kHz)

Time (µs)

+10

0

–10

0

Out

put V

olta

ge (

V)

STEP RESPONSE

10050

Time (µs)

+10

0

–10

0

Out

put V

olta

ge (

V)

STEP RESPONSE

500 1000

TYPICAL PERFORMANCE CURVESTA = +25°C, VS = ±15V unless otherwise noted.

100

0

100M10M

ISOLATION VOLTAGEvs FREQUENCY

TypicalPerformance

Frequency (Hz)

100k10k

Max DC Rating

1k

Pea

k Is

olat

ion

Vol

tage

DegradedPerformance

100 1k 1M

2.1k

IMR vs FREQUENCY

1M1

Frequency (Hz)

160

140

120

100

80

60

40

10 100 100k10k1k

IMR

(dB

)

5

®

ISO122

TYPICAL PERFORMANCE CURVESTA = +25°C, VS = ±15V unless otherwise noted.

PSRR vs FREQUENCY60

40

20

0

Frequency (Hz)

1 10 100 1k 10k 100k 1M

54

PS

RR

(dB

)

–VS1

, –VS2

+VS1

, +VS2

Frequency (Hz)

100mA

10mA

1mA

100µA

10µA

1µA

0.1µA

1 10 100 1k 10k 100k 1M

ISOLATION LEAKAGE CURRENTvs FREQUENCY

Leak

age

Cur

rent

(rm

s)

1500Vrms

240Vrms

Input Frequency

0 500kHz 1MHz 1.5MHz

0

–10

–20

–30

–40

250

200

150

100

50

VO

UT

/ V

IN d

Bm

SIGNAL RESPONSE TOINPUTS GREATER THAN 250kHz

Fre

quen

cy O

ut

100kHzVOUT

/VIN Freq

Out

(NOTE: Shaded area shows aliasing frequencies that cannotbe removed by a low-pass filter at the output.)

6

®

ISO122

THEORY OF OPERATIONThe ISO122 isolation amplifier uses an input and an outputsection galvanically isolated by matched 1pF isolating ca-pacitors built into the plastic package. The input is duty-cycle modulated and transmitted digitally across the barrier.The output section receives the modulated signal, converts itback to an analog voltage and removes the ripple componentinherent in the demodulation. Input and output sections arefabricated, then laser trimmed for exceptional circuitry match-ing common to both input and output sections. The sectionsare then mounted on opposite ends of the package with theisolating capacitors mounted between the two sections. Thetransistor count of the ISO122 is 250 transistors.

MODULATOR

An input amplifier (A1, Figure 1) integrates the differencebetween the input current (V

IN/200kΩ) and a switched

±100µA current source. This current source is implementedby a switchable 200µA source and a fixed 100µA currentsink. To understand the basic operation of the modulator,assume that V

IN = 0.0V. The integrator will ramp in one

direction until the comparator threshold is exceeded. Thecomparator and sense amp will force the current source toswitch; the resultant signal is a triangular waveform with a50% duty cycle. The internal oscillator forces the currentsource to switch at 500kHz. The resultant capacitor drive isa complementary duty-cycle modulation square wave.

DEMODULATOR

The sense amplifier detects the signal transitions across thecapacitive barrier and drives a switched current source intointegrator A2. The output stage balances the duty-cyclemodulated current against the feedback current through the200kΩ feedback resistor, resulting in an average value at the

VOUT

pin equal to VIN

. The sample and hold amplifiers in theoutput feedback loop serve to remove undesired ripplevoltages inherent in the demodulation process.

BASIC OPERATIONSIGNAL AND SUPPLY CONNECTIONS

Each power supply pin should be bypassed with 1µF tanta-lum capacitors located as close to the amplifier as possible.The internal frequency of the modulator/demodulator is setat 500kHz by an internal oscillator. Therefore, if it is desiredto minimize any feedthrough noise (beat frequencies) froma DC/DC converter, use a π filter on the supplies (see Figure4). ISO122 output has a 500kHz ripple of 20mV, which canbe removed with a simple two pole low-pass filter with a100kHz cutoff using a low cost op amp. See Figure 4.

The input to the modulator is a current (set by the 200kΩintegrator input resistor) that makes it possible to have aninput voltage greater than the input supplies, as long as theoutput supply is at least ±15V. It is therefore possible whenusing an unregulated DC/DC converter to minimize PSRrelated output errors with ±5V voltage regulators on theisolated side and still get the full ±10V input and outputswing. An example of this application is shown in Figure10.

CARRIER FREQUENCY CONSIDERATIONS

The ISO122 amplifier transmits the signal across the isola-tion barrier by a 500kHz duty cycle modulation technique.For input signals having frequencies below 250kHz, thissystem works like any linear amplifier. But for frequenciesabove 250kHz, the behavior is similar to that of a samplingamplifier. The signal response to inputs greater than 250kHz

1pF

200µA

100µA

200kΩ

Isolation Barrier

1pF

1pF

200µA

100µA200kΩVIN

+

–

Osc

Gnd 1 –VS1

+VS1

VOUT

S/HG = 6

S/HG = 1

Gnd 2+VS2 –VS2

–

+A2

SenseSense

FIGURE 1. Block Diagram.

A1

150pF 150pF

1pF

| |

7

®

ISO122

performance curve shows this behavior graphically; at inputfrequencies above 250kHz the device generates an outputsignal component of reduced magnitude at a frequencybelow 250kHz. This is the aliasing effect of sampling atfrequencies less than 2 times the signal frequency (theNyquist frequency). Note that at the carrier frequency and itsharmonics, both the frequency and amplitude of the aliasinggo to zero.

ISOLATION MODE VOLTAGE INDUCED ERRORS

IMV can induce errors at the output as indicated by the plotsof IMV vs Frequency. It should be noted that if the IMVfrequency exceeds 250kHz, the output also will displayspurious outputs (aliasing), in a manner similar to that forV

IN > 250kHz and the amplifier response will be identical to

that shown in the Signal Response to Inputs Greater Than250kHz performance curve. This occurs because IMV-induced errors behave like input-referred error signals. Topredict the total error, divide the isolation voltage by theIMR shown in the IMR vs Frequency curve and compute theamplifier response to this input-referred error signal fromthe data given in the Signal Response to Inputs Greater than250kHz performance curve. For example, if a 800kHz1000Vrms IMR is present, then a total of [(–60dB) +(–30dB)] x (1000V) = 32mV error signal at 200kHz plus a1V, 800kHz error signal will be present at the output.

HIGH IMV dV/dt ERRORS

As the IMV frequency increases and the dV/dt exceeds1000V/µs, the sense amp may start to false trigger, and theoutput will display spurious errors. The common modecurrent being sent across the barrier by the high slew rate isthe cause of the false triggering of the sense amplifier.Lowering the power supply voltages below ±15V maydecrease the dV/dt to 500V/µs for typical performance.

Isolation Barrier

VIN

1µF

+VS2

–VS1+VS1

1µF1µF

Gnd

–VS2

1µF

VOUT

Gnd

±VS1 ±VS2

FIGURE 2. Basic Signal and Power Connections.

HIGH VOLTAGE TESTING

Burr-Brown Corporation has adopted a partial discharge testcriterion that conforms to the German VDE0884 Optocou-pler Standards. This method requires the measurement ofminute current pulses (<5pC) while applying 2400Vrms,60Hz high voltage stress across every ISO122 isolationbarrier. No partial discharge may be initiated to pass thistest. This criterion confirms transient overvoltage (1.6 x1500Vrms) protection without damage to the ISO122. Lifetestresults verify the absence of failure under continuous ratedvoltage and maximum temperature.

This new test method represents the “state of the art” fornon-destructive high voltage reliability testing. It is based onthe effects of non-uniform fields that exist in heterogeneousdielectric material during barrier degradation. In the case ofvoid non-uniformities, electric field stress begins to ionizethe void region before bridging the entire high voltagebarrier. The transient conduction of charge during and afterthe ionization can be detected externally as a burst of 0.01-0.1µs current pulses that repeat on each AC voltage cycle.The minimum AC barrier voltage that initiates partial dis-charge is defined as the “inception voltage.” Decreasing thebarrier voltage to a lower level is required before partialdischarge ceases and is defined as the “extinction voltage.”We have characterized and developed the package insulationprocesses to yield an inception voltage in excess of 2400Vrmsso that transient overvoltages below this level will notdamage the ISO122. The extinction voltage is above1500Vrms so that even overvoltage induced partial dis-charge will cease once the barrier voltage is reduced to the1500Vrms (rated) level. Older high voltage test methodsrelied on applying a large enough overvoltage (above rating)to break down marginal parts, but not so high as to damagegood ones. Our new partial discharge testing gives us moreconfidence in barrier reliability than breakdown/no break-down criteria.

ISO122P

ISO150 A1

A0

–15V+15V +15V –15V

12

910 7

8

VOUT

21

15 15

16

PGA102

7

6

8VIN

3 4 5

FIGURE 3. Programmable-Gain Isolation Channel withGains of 1, 10, and 100.

8

®

ISO122

FIGURE 4. Optional π Filter to Minimize Power Supply Feedthrough Noise; Output Filter to Remove 500kHz Carrier Ripple.For more information concerning output filter refer to AB-023.

Isolation Barrier

–VS1

10µH10µH 10µH

10µH

1µF

1µF 1µF 1µF

1µF

1µF 1µF 1µF

±VS1

VIN ISO122

+VS1

+VS2

–VS2

Gnd

13kΩ

13kΩ

100pF

+

–6

VOUT

= –VIN

Gnd

4700pF

385Ω

Charge/DischargeControl

10kΩ

10kΩ

25kΩ

25kΩ

7

–V+V

25kΩ

25kΩ+

– INA105

1

3 V = e50

2

5

6

V = e1

2

ControlSection

Mul

tiple

xer

+V

ISO122P

10kΩ

10kΩ15

9

7

8

–V

+V

ISO122P

9

7

8

–V

4e49

=12V

e50

=12V

e1 = 12V

e2 = 12V

FIGURE 5. Battery Monitor for a 600V Battery Power System. (Derives Input Power from the Battery.)

10

±VS2

This Section Repeated 49 Times.

10

1

2

16

15

162

1

OPA602

2

3

2

9

®

ISO122

10.0V

ThermocoupleREF102

27kΩR1

R4

+In

–In

–15V

2

14

13

1RG

12

10

3

54

11

R5R3

R2

IsothermalBlock with1N4148 (1)

Ground Loop Through Conduit

100Zero Adj

R6

50Ω100Ω

+15V

+15V –15V +15V –15V

12

9

8

16

15 10 7 VOUT

ISO122P

FIGURE 6. Thermocouple Amplifier with Ground Loop Elimination, Cold Junction Compensation, and Up-scale Burn-out.

SEEBACKISA COEFFICIENT R2 R4

TYPE MATERIAL ( µV/°C) (R3 = 100Ω) (R

5 + R

6 = 100Ω)

ChromelE Constantan 58.5 3.48kΩ 56.2kΩ

IronJ Constantan 50.2 4.12kΩ 64.9kΩ

ChromelK Alumel 39.4 5.23kΩ 80.6kΩ

CopperT Constantan 38.0 5.49kΩ 84.5kΩ

NOTE: (1) –2.1mV/°C at 2.00µA.

1MΩ

INA101

2

6 4

+15V

0.01

µF

6

5

RTD(PT100)

1mA1mA

2mA

R2 = 2.5kΩ

–V

0V-5V

+V

Gnd

–VS = –15Von PWS740

4-20mA

ISO122P3

214

9

8

2

11

8

74

3

VOUT

10

7

12

4

10

XTR101

+VS =15V

on PWS740

R1 = 100Ω

10

11

5, 13

1516

15

16

1

FIGURE 7. Isolated 4-20mA Instrument Loop. (RTD shown.)

RS

RCV420

10

®

ISO122

FIGURE 8. Isolated Power Line Monitor.

MPY100

X

Y

(V2)P

L= V

2(R

D1 + R

D2)

RS RD2

XY10

(V1)

10kΩ

2

3

6

0.01µFISO122P

–V

(V3)V

L= V

3(R

D1 + R

D2)

RD2

+VISO122P

2kΩIL= V1

10RS

0.1µF

2kΩ

+V

9715

16

8

Load IL

RD2

RD1VL

RS

0.3µF

0.3µF

PWS740-363

1 4

2 13

46 5

PWS740-2

To PWS740-1

0.3µF

0.3µF

97

8

15

16

41PWS740-33 6

PWS740-2

To PWS740-1

13 2

456

2 1

12

10

10

–V

OPA602

–

+

11

®

ISO122

FIGURE 9. Three-Port, Low-Cost, Four-Channel Isolated, Data Acquisition System.

+V

Channel 2(Same as Channel 1.)

PWS740-1

4 65

33

4 4

0.3µF

ISO122P

0.3µF

0.3µF

64

1 1

66

16

15 7

0.3µF

Channel 1

1

Channel 4(Same as Channel 1.)

Channel 3(Same as Channel 1.)

98

2

VINV

OUT

123123

20µH PWS740-2 PWS740-2

50.3µF

10µF

6

3

4

8

5

10

PWS740-3 PWS740-3

12

®

ISO122

+15V

9

7

810

VIN , up to± 10V Swing

216

1–15

0.1µF0.1µF

0.33µF 0.33µF4

PWS740–3

VOUT

To PWS740–2,–1

NOTE: The input supplies can be subregulated to ±5V to reducePSR related errors without reducing the ±10V input range.

12

3

1

2

3MC78L05

+5VRegulator

–5VRegulatorMC79L05

VS

INPUT RANGE(V) (V)(1)

20+ –2 to +1015 –2 to +512 –2 to +2

FIGURE 10. Improved PSR Using External Regulator.

FIGURE 11. Single Supply Operation of the ISO122P Isolation Amplifier. For additional information see AB-009.

NOTE: Since the amplifier is unity gain, the inputrange is also the output range. The output can go to–2V since the output section of the ISO amp operatesfrom dual supplies.

ISO122P

R1 R2

R4

INA105Difference Amp

R3

RS

2

3

4

IN46895.1V

Reference

5

7

6

1VIN

Signal Source

+

NOTE: (1) Select to match R .S

10kΩ

15 1

9

V (+15V)S1

+V (+15V)S2

–V (–15V)S2

162

–VS1

Com 2

V = VOUT IN7

8

10

In

Gnd

ISO122

RC(1)

ISO122P

ISO122P

13

®

ISO122

15 16

1 2

10 9

ISO122P INPUT

SECTION OUTPUT SECTION

7 8

Gnd VIN V– V+

V+ V– VO Gnd

HPR117

6 5 4 2 1

Output Gnd

VO

VIN

+15V

–15V

Auxiliary Isolated Power Output

–15V, 20mA

+15V, 20mA Input Gnd

–15V, 20mA

+15V, 20mA

15 16

1 2

10 9

ISO122P INPUT

SECTION OUTPUT SECTION

7 8

Gnd VIN V– V+

V+ V– VO Gnd

HPR117

4 5 6 1 2

VIN

Input Gnd

+15V, 20mA

–15V, 20mA

Auxiliary Isolated Power Output

HPR117

6 5 4 1

VO

Output Gnd

Auxiliary Isolated Power Output

Gnd +15V

2

FIGURE 13. Powered ISO Amp with Three-Port Isolation. For additional information refer to AB-024.

FIGURE 12. Input-Side Powered ISO Amp. For additional information refer to AB-024.

IMPORTANT NOTICE

Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinueany product or service without notice, and advise customers to obtain the latest version of relevant informationto verify, before placing orders, that information being relied on is current and complete. All products are soldsubject to the terms and conditions of sale supplied at the time of order acknowledgment, including thosepertaining to warranty, patent infringement, and limitation of liability.

TI warrants performance of its semiconductor products to the specifications applicable at the time of sale inaccordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extentTI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarilyperformed, except those mandated by government requirements.

Customers are responsible for their applications using TI components.

In order to minimize risks associated with the customer’s applications, adequate design and operatingsafeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or representthat any license, either express or implied, is granted under any patent right, copyright, mask work right, or otherintellectual property right of TI covering or relating to any combination, machine, or process in which suchsemiconductor products or services might be or are used. TI’s publication of information regarding any thirdparty’s products or services does not constitute TI’s approval, warranty or endorsement thereof.

Copyright 2000, Texas Instruments Incorporated