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ISO 124
ISO124
ISO
124
Precision Lowest Cost ISOLATION AMPLIFIER
FEATURES
q 100% TESTED FOR HIGH-VOLTAGE BREAKDOWN q RATED 1500Vrms q HIGH IMR: 140dB at 60Hz q 0.010% max NONLINEARITY q BIPOLAR OPERATION: VO = 10V q 16-PIN PLASTIC DIP AND 28-LEAD SOIC q EASE OF USE: Fixed Unity Gain Configuration q 4.5V to 18V SUPPLY RANGE
APPLICATIONS
q INDUSTRIAL PROCESS CONTROL: Transducer Isolator, Isolator for Thermocouples, RTDs, Pressure Bridges, and Flow Meters, 4mA to 20mA Loop Isolation q GROUND LOOP ELIMINATION q MOTOR AND SCR CONTROL q POWER MONITORING q PC-BASED DATA ACQUISITION q TEST EQUIPMENT
DESCRIPTION
The ISO124 is a precision isolation amplifier incorporating a novel duty cycle modulation-demodulation technique. The signal is transmitted digitally across a 2pF differential capacitive barrier. With digital modulation the barrier characteristics do not affect signal integrity, resulting in excellent reliability and good high frequency transient immunity across the barrier. Both barrier capacitors are imbedded in the plastic body of the package. The ISO124 is easy to use. No external components are required for operation. The key specifications are 0.010% max nonlinearity, 50kHz signal bandwidth, and 200V/C VOS drift. A power supply range of 4.5V to 18V and quiescent currents of 5.0mA on VS1 and 5.5mA on VS2 make these amplifiers ideal for a wide range of applications. The ISO124 is available in 16-pin plastic DIP and 28lead plastic surface mount packages.
VIN
VOUT
-VS2 Gnd +VS2 -VS1 Gnd +VS1
International Airport Industrial Park * Mailing Address: PO Box 11400, Tucson, AZ 85734 * Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 * Tel: (520) 746-1111 * Twx: 910-952-1111 Internet: http://www.burr-brown.com/ * FAXLine: (800) 548-6133 (US/Canada Only) * Cable: BBRCORP * Telex: 066-6491 * FAX: (520) 889-1510 * Immediate Product Info: (800) 548-6132
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1997 Burr-Brown Corporation
PDS-1405A 1
Printed in U.S.A. September, 1997
ISO124
SPECIFICATIONS
At TA = +25C , VS1 = VS2 = 15V, and RL = 2k, unless otherwise noted. ISO124P, U PARAMETER ISOLATION Rated Voltage, continuous ac 60Hz 100% Test (1) Isolation Mode Rejection Barrier Impedance Leakage Current at 60Hz GAIN Nominal Gain Gain Error Gain vs Temperature Nonlinearity(2) INPUT OFFSET VOLTAGE Initial Offset vs Temperature vs Supply Noise INPUT Voltage Range Resistance OUTPUT Voltage Range Current Drive Capacitive Load Drive Ripple Voltage(3) FREQUENCY RESPONSE Small Signal Bandwidth Slew Rate Settling Time 0.1% 0.01% Overload Recovery Time POWER SUPPLIES Rated Voltage Voltage Range Quiescent Current: VS1 VS2 TEMPERATURE RANGE Specification Operating Storage Thermal Resistance, JA JC 10 CONDITIONS MIN 1500 2400 140 1014 || 2 0.18 1 0.05 10 0.005 20 200 2 4 12.5 200 12.5 15 0.1 20 50 2 VO = 10V 50 350 150 15 5.0 5.5 TYP MAX UNITS Vac Vac dB || pF Arms V/V %FSR ppm/C %FSR mV V/C mV/V V/Hz V k V mA F mVp-p kHz V/s s s s V V mA mA C C C C/W C/W
1s, 5pc PD 60Hz VISO = 240Vrms VO = 10V
0.5
0.50 0.010 50
10 5
4.5
18 7.0 7.0 +85 +85 +85
-25 -25 -40 100 65
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 expressed as the ratio of deviation to FSR. (3) Ripple frequency is at carrier frequency (500kHz).
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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ISO124
2
CONNECTION DIAGRAM
Top View --P Package Top View--U Package
+VS1 -VS1
1 2
16 15
Gnd VIN
+VS1 -VS1
1 2
28 27
Gnd VIN
VOUT Gnd
7 8
10 9
-VS2 +VS2
VOUT Gnd
13 14
16 15
-VS2 +VS2
PACKAGE INFORMATION
PRODUCT ISO124P ISO124U PACKAGE 16-Pin Plastic DIP 28-Lead Plastic SOIC PACKAGE DRAWING NUMBER(1) 238 217-1
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage ................................................................................... 18V VIN ......................................................................................................100V Continuous Isolation Voltage ..................................................... 1500Vrms Junction Temperature .................................................................... +150C Storage Temperature ....................................................................... +85C Lead Temperature (soldering, 10s) ................................................ +300C Output Short to Common ......................................................... Continuous NOTE: (1) Stresses above these ratings may cause permanent damage.
NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book.
ORDERING INFORMATION
PRODUCT ISO124P ISO124U PACKAGE 16-Pin Plastic DIP 28-Lead Plastic SOIC NONLINEARITY MAX %FSR 0.010 0.010
ELECTROSTATIC DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
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ISO124
TYPICAL PERFORMANCE CURVES
At TA = +25C, and VS = 15V, unless otherwise noted.
SINE RESPONSE (f = 2kHz)
SINE RESPONSE (f = 20kHz)
Output Voltage (V)
Output Voltage (V)
+10
+10
0
0
-10
-10
0
500 Time (s)
1000
0
50 Time (s)
100
STEP RESPONSE
STEP RESPONSE
Output Voltage (V)
0
Output Voltage (V)
+10
+10
0
-10
-10
0
500 Time (s)
1000
0
50 Time (s)
100
ISOLATION VOLTAGE vs FREQUENCY
IMR vs FREQUENCY 160
Max DC Rating 2.1k
140 120
IMR (dB)
100M Degraded Performance
Peak Isolation Voltage
1k
100 80
100 Typical Performance 0 100 1k 10k 100k Frequency (Hz) 1M 10M
60 40 1 10 100 1k Frequency (Hz) 10k 100k 1M
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ISO124
4
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25C, and VS = 15V, unless otherwise noted.
PSRR vs FREQUENCY 60 54 10mA 40 +VS1, +VS2 -VS1, -VS2 20 Leakage Current (rms) 1mA 100mA
ISOLATION LEAKAGE CURRENT vs FREQUENCY
PSRR (dB)
1500Vrms 100A 10A 240Vrms 1A
0 1 10 100 1k Frequency (Hz) 10k 100k 1M
0.1A 1 10 100 1k Frequency (Hz) 10k 100k 1M
SIGNAL RESPONSE TO INPUTS GREATER THAN 250kHz VOUT/VIN 0
VOUT/VIN (dBm)
100kHz Frequency Out 250 200 150 100 50
Frequency Out
-10 -20 -30 -40
0
500k
1M
1.5M
Input Frequency (Hz) (NOTE: Shaded area shows aliasing frequencies that cannot be removed by a low-pass filter at the output.)
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ISO124
THEORY OF OPERATION
The ISO124 isolation amplifier uses an input and an output section galvanically isolated by matched 1pF isolating capacitors built into the plastic package. The input is dutycycle modulated and transmitted digitally across the barrier. The output section receives the modulated signal, converts it back to an analog voltage and removes the ripple component inherent in the demodulation. Input and output sections are fabricated, then laser trimmed for exceptional circuitry matching common to both input and output sections. The sections are then mounted on opposite ends of the package with the isolating capacitors mounted between the two sections. The transistor count of the ISO124 is 250 transistors. MODULATOR An input amplifier (A1, Figure 1) integrates the difference between the input current (VIN/200k) and a switched 100A current source. This current source is implemented by a switchable 200A source and a fixed 100A current sink. To understand the basic operation of the modulator, assume that VIN = 0.0V. The integrator will ramp in one direction until the comparator threshold is exceeded. The comparator and sense amp will force the current source to switch; the resultant signal is a triangular waveform with a 50% duty cycle. The internal oscillator forces the current source to switch at 500kHz. The resultant capacitor drive is a complementary duty-cycle modulation square wave. DEMODULATOR The sense amplifier detects the signal transitions across the capacitive barrier and drives a switched current source into integrator A2. The output stage balances the duty-cycle
modulated current against the feedback current through the 200k feedback resistor, resulting in an average value at the VOUT pin equal to VIN. The sample and hold amplifiers in the output feedback loop serve to remove undesired ripple voltages inherent in the demodulation process.
BASIC OPERATION
SIGNAL AND SUPPLY CONNECTIONS Each power supply pin should be bypassed with 1F tantalum capacitors located as close to the amplifier as possible. The internal frequency of the modulator/demodulator is set at 500kHz by an internal oscillator. Therefore, if it is desired to minimize any feedthrough noise (beat frequencies) from a DC/DC converter, use a filter on the supplies (see Figure 4). ISO124 output has a 500kHz ripple of 20mV, which can be removed with a simple two pole low-pass filter with a 100kHz cutoff using a low cost op amp (see Figure 4). The input to the modulator is a current (set by the 200k integrator input resistor) that makes it possible to have an input voltage greater than the input supplies, as long as the output supply is at least 15V. It is therefore possible when using an unregulated DC/DC converter to minimize PSR related output errors with 5V voltage regulators on the isolated side and still get the full 10V input and output swing. An example of this application is shown in Figure 9. CARRIER FREQUENCY CONSIDERATIONS The ISO124 amplifier transmits the signal across the isolation barrier by a 500kHz duty cycle modulation technique. For input signals having frequencies below 250kHz, this system works like any linear amplifier. But for frequencies
Isolation Barrier 200A 1pF 1pF
200A
1pF Sense 100A 200k VIN VOUT A2 A1 S/H G=1 Osc S/H G=6 150pF 1pF Sense 100A 150pF 200k
+VS1
Gnd 1
-VS1
+VS2
Gnd 2
-VS2
FIGURE 1. Block Diagram.
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ISO124
6
above 250kHz, the behavior is similar to that of a sampling amplifier. The signal response to inputs greater than 250kHz performance curve shows this behavior graphically; at input frequencies above 250kHz the device generates an output signal component of reduced magnitude at a frequency below 250kHz. This is the aliasing effect of sampling at frequencies less than 2 times the signal frequency (the Nyquist frequency). Note that at the carrier frequency and its harmonics, both the frequency and amplitude of the aliasing go to zero. ISOLATION MODE VOLTAGE INDUCED ERRORS IMV can induce errors at the output as indicated by the plots of IMV vs Frequency. It should be noted that if the IMV frequency exceeds 250kHz, the output also will display spurious outputs (aliasing) in a manner similar to that for VIN >250kHz and the amplifier response will be identical to that shown in the "Signal Response to Inputs Greater Than 250kHz" typical performance curve. This occurs because IMV-induced errors behave like inputreferred error signals. To predict the total error, divide the isolation voltage by the IMR shown in the "IMR versus Frequency" typical performance curve and compute the amplifier response to this input-referred error signal from the data given in the "Signal Response to Inputs Greater Than 250kHz" typical performance curve. For example, if a 800kHz 1000Vrms IMR is present, then a total of [(-60dB) + (-30dB)] x (1000V) = 32mV error signal at 200kHz plus a 1V, 800kHz error signal will be present at the output. HIGH IMV dV/dt ERRORS As the IMV frequency increases and the dV/dt exceeds 1000V/s, the sense amp may start to false trigger, and the output will display spurious errors. The common-mode current being sent across the barrier by the high slew rate is the cause of the false triggering of the sense amplifier. Lowering the power supply voltages below 15V may decrease the dV/dt to 500V/s for typical performance.
Isolation Barrier
HIGH VOLTAGE TESTING Burr-Brown Corporation has adopted a partial discharge test criterion that conforms to the German VDE0884 Optocoupler Standards. This method requires the measurement of minute current pulses (<5pC) while applying 2400Vrms, 60Hz high voltage stress across every ISO124 isolation barrier. No partial discharge may be initiated to pass this test. This criterion confirms transient overvoltage (1.6 x 1500Vrms) protection without damage to the ISO124. Lifetest results verify the absence of failure under continuous rated voltage and maximum temperature. This new test method represents the "state-of-the art" for non-destructive high voltage reliability testing. It is based on the effects of non-uniform fields that exist in heterogeneous dielectric material during barrier degradation. In the case of void non-uniformities, electric field stress begins to ionize the void region before bridging the entire high voltage barrier. The transient conduction of charge during and after the ionization can be detected externally as a burst of 0.010.1s current pulses that repeat on each ac voltage cycle. The minimum ac barrier voltage that initiates partial discharge is defined as the "inception voltage." Decreasing the barrier voltage to a lower level is required before partial discharge ceases and is defined as the "extinction voltage." We have characterized and developed the package insulation processes to yield an inception voltage in excess of 2400Vrms so that transient overvoltages below this level will not damage the ISO124. The extinction voltage is above 1500Vrms so that even overvoltage induced partial discharge will cease once the barrier voltage is reduced to the 1500Vrms (rated) level. Older high voltage test methods relied on applying a large enough overvoltage (above rating) to break down marginal parts, but not so high as to damage good ones. Our new partial discharge testing gives us more confidence in barrier reliability than breakdown/no breakdown criteria.
ISO150
A0 A1
VIN Gnd
ISO124 Gnd +VS2 -VS1 +VS1 VS1 1F 1F 1F
-VS2
VOUT
+15V -15V 1 2 6 VIN 1 15 ISO124
+15V -15V
9 10 8 7 VOUT
VS2 1F
2 15 7 PGA102 8 5 4 3
16
FIGURE 2. Basic Signal and Power Connections.
FIGURE 3. Programmable-Gain Isolation Channel with Gains of 1, 10, and 100.
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7
ISO124
C2 1000pF Isolation Barrier
R1 4.75k VIN ISO124 -VS2 +VS2 Gnd1 -VS1 +VS1 10H 1F 1F 1F 1F 10H VS1 10H 1F 1F 1F 1F 10H VS2 Gnd2
R2 9.76k
OPA237
VOUT = VIN
C1 220pF
FIGURE 4. Optional Filter to Minimize Power Supply Feedthrough Noise; Output Filter to Remove 500kHz Carrier Ripple. For more information concerning output filter refer to AB-023 and AB-034.
This Section Repeated 49 Times. ISO124 10k e1 = 12V 10k 15 10 e2 = 12V 16 2 -V +V 1 9 7 8 V= e1 2
Charge/Discharge Control
Multiplexer
Control Section
ISO124 +V 15 1 9 e50 = 12V 10k 10 2 10k 16 -V 3 1 25k 7 8 2 25k
+V -V 7 INA105 25k 5 4
e49 = 12V
6 25k V= e50 2
FIGURE 5. Battery Monitor for a 600V Battery Power System. (Derives input power from the battery.)
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ISO124
8
+15V
2 10.0V Thermocouple R1 27k R4 +15V 6 REF102 4 +15V -15V +15V -15V
Isothermal Block with 1N4148(1) RG 1M R2
2 7 +In 1 8 INA114 or INA128 -In 4 3 R3 100 R5 50 -15V R6 100 Zero Adj ISA TYPE E 6 5 15
1 2 9 10 8 16 7 VOUT ISO124
MATERIAL Chromel Constantan Iron Constantan Chromel Alumel Copper Constantan
SEEBACK COEFFICIENT (V/C) 58.5 50.2 39.4 38.0
R2 (R3 = 100) 3.48k 4.12k 5.23k 5.49k
R4 (R5 + R6 = 100) 56.2k 64.9k 80.6k 84.5k
Ground Loop Through Conduit NOTE: (1) -2.1mV/C at 2.00A.
J K T
FIGURE 6. Thermocouple Amplifier with Ground Loop Elimination, Cold Junction Compensation, and Up-scale Burn-out.
13 0.8mA 0.8mA RG 4 2 RTD (PT100) RZ(1) RCM 1k 3
1
14
10 0.01F 7
4-20mA +VS = 15V on PWS740 16 3 15 14 15 1 ISO124 +V 9 7 8 10 2 16 -V Gnd -VS = -15V on PWS740
XTR105
6
10
2 RCV420 5, 13 4 11 12
VOUT 0V - 5V
1.6mA
NOTE: (1) RZ = RTD resistance at minimum measured temperature.
FIGURE 7. Isolated 4-20mA Instrument Loop. (RTD shown.)
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9
ISO124
RS
VL Load 2k 10k IL
RD1
V+
(R)
RD2 2 2k 3 IL = 16 0.01F 9 15 ISO124 8 V+ 10 2 1 9 0.47F 7 0.47F 8 10 16 2 1 V- 1 5 6 7 2 X MPY634 0.47F DCP011515 Y 0.47F 0.47F XY 10 (V2) 15 ISO124 V- 7 V1 10RS OPA237 6 (V1)
ISO124
PL = V2 (RD1 + RD2) RS RD2 5 6 7 (V3) VL = V3 (RD1 + RD2) DCP011515 RD2
10
1
2
0.47F
FIGURE 8. Isolated Power Line Monitor.
+15V
VIN, up to 10V Swing ISO124
9 7 8 10 2 1 16 -15V VOUT
+5V Regulator MC78L05 2
0.1F 0.1F 1 1 3
-5V Regulator MC79L05
0.47F 3 2
0.47F 0.47F
7
6
5
2
1
DCP011515
NOTE: The input supplies can be subregulated to 5V to reduce PSR related errors without reducing the 10V input range.
FIGURE 9. Improved PSR Using External Regulator.
VS1 (+15V) 7 VS (V) 20+ 15 12 INPUT RANGE (V)(1) -2 to +10 -2 to +5 -2 to +2 2 R1 R2 6 15 INA105 Difference Amp 5 10k 1 In ISO124 Gnd 16 4 Reference IN4689 5.1V 2 -VS1 -VS2 (-15V) 10 8 Com 2 9 7 VOUT = VIN +VS2 (+15V)
Signal Source VIN + RS
3
R3
R4
1
RC
(1)
NOTE: (1) Select to match RS .
NOTE: Since the amplifier is unity gain, the input range is also the output range. The output can go to -2V since the output section of the ISO amp operates from dual supplies.
FIGURE 10. Single Supply Operation of the ISO124 Isolation Amplifier. For additional information refer to AB-009.
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11
ISO124
1
2
5
6
7
DCP011515
0.47F
0.47F 0.47F
VIN Input Gnd
-15V, 20mA
+15V, 20mA 16 15 10 V- 9 V+ Auxiliary Isolated Power Output Gnd VIN
INPUT SECTION
ISO124
OUTPUT SECTION
V+ 1 +15V -15V
V- 2
VO 7
Gnd 8 Output Gnd VO
FIGURE 11. Input-Side Powered ISO Amp.
+15V Gnd
1
2
5
6
7
DCP011515
DCP011515
7 0.47F
6
5 0.47F 0.47F
2
1 0.47F 0.47F -15V, 20mA +15V, 20mA
VIN Input Gnd 16 15 10 V- 9 V+
Gnd VIN
Auxiliary Isolated Power Output
INPUT SECTION Auxiliary Isolated Power Output +15V, 20mA -15V, 20mA
ISO124
OUTPUT SECTION
V+ 1
V- 2
VO 7
Gnd 8 Output Gnd VO
FIGURE 12. Powered ISO Amp with Three-Port Isolation.
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ISO124
12
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