® ISO124 ISO 124 ISO 124 Precision Lowest Cost ISOLATION AMPLIFIER FEATURES APPLICATIONS ● 100% TESTED FOR HIGH-VOLTAGE BREAKDOWN ● INDUSTRIAL PROCESS CONTROL: Transducer Isolator, Isolator for Thermocouples, RTDs, Pressure Bridges, and Flow Meters, 4mA to 20mA Loop Isolation ● RATED 1500Vrms ● HIGH IMR: 140dB at 60Hz ● 0.010% max NONLINEARITY ● GROUND LOOP ELIMINATION ● MOTOR AND SCR CONTROL ● POWER MONITORING ● BIPOLAR OPERATION: VO = ±10V ● 16-PIN PLASTIC DIP AND 28-LEAD SOIC ● EASE OF USE: Fixed Unity Gain Configuration ● ±4.5V to ±18V SUPPLY RANGE ● PC-BASED DATA ACQUISITION ● 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 200µV/°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. VIN VOUT –VS2 Gnd +VS2 –VS1 Gnd +VS1 The ISO124 is available in 16-pin plastic DIP and 28lead plastic surface mount packages. 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 ® © 1997 Burr-Brown Corporation PDS-1405A 1 ISO124 Printed in U.S.A. September, 1997 SPECIFICATIONS At TA = +25°C , VS1 = VS2 = ±15V, and RL = 2kΩ, unless otherwise noted. ISO124P, U PARAMETER CONDITIONS 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) MIN MAX UNITS 0.5 Vac Vac dB Ω || pF µArms 1500 2400 1s, 5pc PD 60Hz 140 1014 || 2 0.18 VISO = 240Vrms VO = ±10V 1 ±0.05 ±10 ±0.005 INPUT OFFSET VOLTAGE Initial Offset vs Temperature vs Supply Noise ±20 ±200 ±2 4 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 TYP ±0.50 ±0.010 ±50 ±12.5 200 V kΩ ±10 ±5 ±12.5 ±15 0.1 20 V mA µF mVp-p 50 2 kHz V/µs 50 350 150 µs µs µs ±4.5 TEMPERATURE RANGE Specification Operating Storage Thermal Resistance, θJA θJC mV µV/°C mV/V µV/√Hz ±10 VO = ±10V POWER SUPPLIES Rated Voltage Voltage Range Quiescent Current: VS1 VS2 V/V %FSR ppm/°C %FSR ±15 ±5.0 ±5.5 –25 –25 –40 ±18 ±7.0 ±7.0 +85 +85 +85 100 65 V V mA mA °C °C °C °C/W °C/W 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. ® ISO124 2 CONNECTION DIAGRAM Top View —P Package Top View—U Package +VS1 1 16 Gnd +VS1 1 28 Gnd –VS1 2 15 VIN –VS1 2 27 VIN VOUT 7 10 –VS2 VOUT 13 16 –VS2 Gnd 8 9 +VS2 Gnd 14 15 +VS2 ABSOLUTE MAXIMUM RATINGS(1) PACKAGE INFORMATION PRODUCT ISO124P ISO124U PACKAGE PACKAGE DRAWING NUMBER(1) 16-Pin Plastic DIP 28-Lead Plastic SOIC 238 217-1 Supply Voltage ................................................................................... ±18V VIN ......................................................................................................±100V Continuous Isolation Voltage ..................................................... 1500Vrms Junction Temperature .................................................................... +150°C Storage Temperature ....................................................................... +85°C Lead Temperature (soldering, 10s) ................................................ +300°C Output Short to Common ......................................................... Continuous NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. NOTE: (1) Stresses above these ratings may cause permanent damage. ORDERING INFORMATION PRODUCT ISO124P ISO124U PACKAGE NONLINEARITY MAX %FSR 16-Pin Plastic DIP 28-Lead Plastic SOIC ±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. ® 3 ISO124 TYPICAL PERFORMANCE CURVES At TA = +25°C, and VS = ±15V, unless otherwise noted. SINE RESPONSE (f = 20kHz) +10 Output Voltage (V) Output Voltage (V) SINE RESPONSE (f = 2kHz) 0 –10 0 500 +10 0 –10 0 1000 50 STEP RESPONSE +10 Output Voltage (V) Output Voltage (V) STEP RESPONSE 0 –10 0 100 Time (µs) Time (µs) 500 +10 0 –10 50 0 1000 Time (µs) 100 Time (µs) ISOLATION VOLTAGE vs FREQUENCY IMR vs FREQUENCY 160 Max DC Rating 140 1k 120 Degraded Performance IMR (dB) Peak Isolation Voltage 2.1k 100 100 80 Typical Performance 60 0 40 100 1k 10k 100k 1M 10M 100M 1 Frequency (Hz) 100 1k Frequency (Hz) ® ISO124 10 4 10k 100k 1M TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, and VS = ±15V, unless otherwise noted. PSRR vs FREQUENCY ISOLATION LEAKAGE CURRENT vs FREQUENCY 60 100mA 54 Leakage Current (rms) 40 +VS1, +VS2 –VS1, –VS2 20 1mA 1500Vrms 100µA 10µA 240Vrms 1µA 0 0.1µA 10 100 1k 10k 100k 1M 1 10 100 Frequency (Hz) 1k 10k 100k 1M Frequency (Hz) SIGNAL RESPONSE TO INPUTS GREATER THAN 250kHz 100kHz VOUT/VIN Frequency Out 0 250 –10 200 –20 150 –30 100 –40 50 0 500k 1M Frequency Out 1 VOUT/VIN (dBm) PSRR (dB) 10mA 1.5M Input Frequency (Hz) (NOTE: Shaded area shows aliasing frequencies that cannot be removed by a low-pass filter at the output.) ® 5 ISO124 THEORY OF OPERATION modulated current against the feedback current through the 200kΩ 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. 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. BASIC OPERATION SIGNAL AND SUPPLY CONNECTIONS Each power supply pin should be bypassed with 1µF 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 π 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). MODULATOR An input amplifier (A1, Figure 1) integrates the difference between the input current (VIN/200kΩ) and a switched ±100µA current source. This current source is implemented by a switchable 200µA source and a fixed 100µA 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. The input to the modulator is a current (set by the 200kΩ 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 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 Isolation Barrier 200µA 200µA 1pF 1pF 1pF Sense 1pF 100µA 100µA Sense 150pF 200kΩ 200kΩ 150pF VIN VOUT A2 A1 S/H G=1 S/H G=6 Osc +VS1 Gnd 1 –VS1 +VS2 FIGURE 1. Block Diagram. ® ISO124 6 Gnd 2 –VS2 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. 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. 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. 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 0.010.1µs 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. HIGH IMV dV/dt ERRORS As the IMV frequency increases and the dV/dt exceeds 1000V/µs, 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/µs for typical performance. Isolation Barrier A0 A1 ISO150 VIN ISO124 –VS2 +15V –15V VOUT 1 Gnd Gnd 2 +VS2 6 –VS1 +VS1 VIN ±VS1 1µF 1µF 1µF +15V –15V ±VS2 1µF 1 2 15 7 PGA102 8 5 4 3 9 15 10 ISO124 7 VOUT 8 16 FIGURE 3. Programmable-Gain Isolation Channel with Gains of 1, 10, and 100. FIGURE 2. Basic Signal and Power Connections. ® 7 ISO124 C2 1000pF Isolation Barrier R1 4.75kΩ VIN R2 9.76kΩ OPA237 VOUT = VIN ISO124 –VS2 C1 220pF +VS2 Gnd2 Gnd1 –VS1 +VS1 10µH 10µH ±VS1 10µH 10µH 1µF ±VS2 1µF 1µF 1µF 1µF 1µF 1µF 1µF 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 and AB-034. This Section Repeated 49 Times. ISO124 +V 10kΩ 1 e1 = 12V 10kΩ 9 V= e1 7 15 2 8 10 e2 = 12V 2 16 Multiplexer –V Charge/Discharge Control ISO124 +V –V +V e49 = 12V 15 7 1 9 e50 = 12V 4 INA105 10kΩ 10 25kΩ 7 5 2 8 25kΩ 2 10kΩ 16 6 –V 25kΩ 3 1 V= e50 2 25kΩ FIGURE 5. Battery Monitor for a 600V Battery Power System. (Derives input power from the battery.) ® ISO124 8 Control Section +15V 2 10.0V 6 Thermocouple R4 R1 27kΩ +15V –15V +15V –15V +15V Isothermal Block with 1N4148(1) 1 2 2 7 +In INA114 or INA128 1 RG 1MΩ 4 REF102 R2 8 ISO124 9 6 10 15 7 VOUT 8 5 –In 4 16 3 R3 100Ω R5 50Ω –15V R6 ISA TYPE 100 Zero Adj E Ground Loop Through Conduit J NOTE: (1) –2.1mV/°C at 2.00µA. K T MATERIAL SEEBACK COEFFICIENT (µV/°C) R2 (R3 = 100Ω) R4 (R5 + R6 = 100Ω) 58.5 3.48kΩ 56.2kΩ 50.2 4.12kΩ 64.9kΩ 39.4 5.23kΩ 80.6kΩ 38.0 5.49kΩ 84.5kΩ Chromel Constantan Iron Constantan Chromel Alumel Copper Constantan FIGURE 6. Thermocouple Amplifier with Ground Loop Elimination, Cold Junction Compensation, and Up-scale Burn-out. 1 13 0.8mA 0.8mA 14 10 4-20mA 3 RG +VS = 15V on PWS740 0.01µF XTR105 4 2 RTD (PT100) 16 7 3 6 1 15 14 2 RCV420 5, 13 4 11 RZ(1) ISO124 +V 15 9 7 10 RCM 1kΩ 8 10 12 0V - 5V 2 16 1.6mA VOUT –V Gnd –VS = –15V on PWS740 NOTE: (1) RZ = RTD resistance at minimum measured temperature. FIGURE 7. Isolated 4-20mA Instrument Loop. (RTD shown.) ® 9 ISO124 ® ISO124 10 0.47µF DCP011515 0.47µF 2 16 15 0.47µF RD2 RD1 FIGURE 8. Isolated Power Line Monitor. 1 VL 5 6 1 ISO124 RS 7 2 V– 10 9 V+ Load IL 8 7 1 2 DCP011515 0.47µF 0.47µF 5 6 1 ISO124 0.47µF 15 16 7 2 V– 10 9 V+ 8 7 Y X 2kΩ 2kΩ 0.01µF OPA237 MPY634 10 XY 3 2 10kΩ 6 (V3) (V2) V1 10RS RD2 VL = V3 (RD1 + RD2) RS RD2 PL = V2 (RD1 + RD2) IL = (V1) +15V 9 VIN, up to ±10V Swing 7 ISO124 VOUT 8 10 2 16 1 –15V 0.1µF 0.1µF +5V Regulator MC78L05 –5V Regulator MC79L05 3 1 1 2 0.47µF 2 3 0.47µF 0.47µF 6 7 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) INPUT RANGE (V)(1) 20+ 15 12 –2 to +10 –2 to +5 –2 to +2 INA105 Difference Amp 2 5 R1 10kΩ 1 6 Signal Source VIN + RS R4 R3 3 +VS2 (+15V) R2 15 9 In 1 Gnd Reference VOUT = VIN 8 16 4 7 ISO124 (1) RC 10 Com 2 2 IN4689 5.1V –VS1 –VS2 (–15V) 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. NOTE: (1) Select to match RS . FIGURE 10. Single Supply Operation of the ISO124 Isolation Amplifier. For additional information refer to AB-009. ® 11 ISO124 1 2 5 6 7 DCP011515 0.47µF 0.47µF 0.47µF VIN –15V, 20mA Input Gnd +15V, 20mA 15 16 10 Gnd VIN INPUT SECTION V+ V– Auxiliary Isolated Power Output V+ OUTPUT SECTION ISO124 V– 1 9 VO 2 Gnd 7 +15V 8 Output Gnd –15V VO FIGURE 11. Input-Side Powered ISO Amp. +15V Gnd 1 2 5 DCP011515 7 6 7 DCP011515 5 2 1 0.47µF 0.47µF 6 0.47µF 0.47µF 0.47µF VIN –15V, 20mA Input Gnd +15V, 20mA 16 10 15 Gnd VIN INPUT SECTION Auxiliary Isolated Power Output V+ 1 V– ISO124 V– 7 +15V, 20mA –15V, 20mA V+ Auxiliary Isolated Power Output OUTPUT SECTION VO 2 9 Gnd 8 Output Gnd VO FIGURE 12. Powered ISO Amp with Three-Port Isolation. ® ISO124 12