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| ISO 100 ISO100 Optically-Coupled Linear ISOLATION AMPLIFIER FEATURES q EASY TO USE, SIMILAR TO AN OP AMP VOUT/IIN = RF, Current Input VOUT/VIN = RF/RIN, Voltage Input q 100% TESTED FOR BREAKDOWN: 750V Continuous Isolation Voltage q ULTRA-LOW LEAKAGE: 0.3A, max, at 240V/60Hz q WIDE BANDWIDTH: 60kHz q 18-PIN DIP PACKAGE APPLICATIONS q INDUSTRIAL PROCESS CONTROL Transducer Sensing (Thermocouples, RTD, Pressure Bridges) 4mA to 20mA Loops Motor and SCR Control Ground Loop Elimination q BIOMEDICAL MEASUREMENTS q TEST EQUIPMENT q DATA ACQUISITION DESCRIPTION The ISO100 is an optically-coupled isolation amplifier. High accuracy, linearity, and time-temperature stability are achieved by coupling light from an LED back to the input (negative feedback) as well as forward to the output. Optical components are carefully matched and the amplifier is actively laser-trimmed to assure excellent tracking and low offset errors. The circuit acts as a current-to-voltage converter with a minimum of 750V (2500V test) between input and output terminals. It also effectively breaks the galvanic connection between input and output commons as indicated by the ultra-low 60Hz leakage current of 0.3A at 250V. Voltage input operation is easily achieved by using one external resistor. Versatility along with outstanding DC and AC performance provide excellent solutions to a variety of challenging isolation problems. For example, the ISO100 is capable of operating in many modes, including: noninverting (unipolar and bipolar) and inverting (unipolar and bipolar) configurations. Two precision current sources are provided to accomplish bipolar operation. Since these are not required for unipolar operation, they are available for external use (see Applications section). Designs using the ISO100 are easily accomplished with relatively few external components. Since VOUT of the ISO100 is simply IINRF, gains can be changed by altering one resistor value. In addition, the ISO100 has sufficient bandwidth (DC to 60kHz) to amplify most industrial and test equipment signals. IREF1 Balance RF IREF2 7 8 Balance 5 6 16 13 14 +In -In 15 17 A1 A2 3 VOUT D1 LED 12 10 -VCC +VCC 18 Input Common D2 9 4 2 Output -VCC +VCC Common 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 (c) 1982 Burr-Brown Corporation PDS-456G 1 Printed in U.S.A. August, 1997 ISO100 SPECIFICATIONS ELECTRICAL At TA = +25C and VCC = 15VDC, unless otherwise specified. ISO100AP PARAMETER ISOLATION Voltage Rated Continuous, AC peak or DC(1) Test Breakdown, DC Rejection(2) DC AC Impedance Leakage Current OFFSET VOLTAGE (RTI) Input Stage (VOSI) Initial Offset vs Temperature vs Input Power Supplies vs Time Output Stage (VOSO) Initial Offset vs Temperature vs Output Power Supplies vs Time Common-Mode Rejection Ratio(2) Common-Mode Range REFERENCE CURRENT SOURCES Magnitude Nominal vs Temperature vs Power Supplies Matching Nominal vs Temperature vs Power Supplies Compliance Voltage Output Resistance FREQUENCY RESPONSE Small Signal Bandwidth Full Power Bandwidth Slew Rate Settling Time TEMPERATURE RANGE Specification Operating Storage Gain = 1V/A Gain = 1V/A, VO = 10V 0.22 0.1% -25 -40 -40 UNIPOLAR OPERATION GENERAL PARAMETERS Input Current Range Linear Operation Without Damage Input Impedance Output Voltage Swing Output Impedance GAIN Initial Error (adjustable to zero) vs Temperature vs Time Nonlinearity(3) CURRENT NOISE 0.01Hz to 10Hz 10Hz 100Hz 1kHz CONDITIONS MIN TYP MAX MIN ISO100BP TYP MAX MIN ISO100CP TYP MAX UNITS 10s RIN = 10k, Gain = 100 60Hz, 480V, RF = 1M RIN = 10k, Gain = 100 240Vrms, 60Hz 750 2500 5 146 400 108 1012||2.5 0.3 T T T T T T T T T T T T T T T T V V pA/V dB pA/V dB ||pF A, rms 500 5 105 1 500 5 105 60Hz, RF = 1M RIN = 10k, Gain = 100 1 3 90 10 T T T T T 300 2 T T 300 2 T T T T T 200 2 T V V/C dB V/kHr V V/C dB V/kHr nA/V dB V 200 2 T 10.5 12 0.3 50 150 0.3 12.5 300 3 T T T T T T T T T T T T T T T T 150 T A ppm/C nA/V nA ppm/C nA/V V kHz kHz V/s s -10 2 x 109 60 5 0.31 100 +15 T T T T T T T T T T T T T T T T +85 +100 +100 T T T T T T T T T T T T C C C -20 -1 0.1 RL = 2k, RF = 1M DC, Open-Loop VO = RF (IIN) 2 0.03 0.05 0.1 IIN = 0.2A 20 1 0.7 0.65 -10 1200 -0.02 +1 0 T T T T T T T T T T T T T T T T A mA V % of FS %/C %/kHr % pAp-p pA/Hz pA/Hz pA/Hz 5 0.07 0.4 1 0.01 T 0.03 T T T T 2 0.05 0.1 1 0.005 T 0.02 T T T T 2 0.03 0.07 ISO100 2 SPECIFICATIONS ELECTRICAL (CONT) At TA = +25C and VCC = 15VDC, unless otherwise specified. ISO100AP PARAMETER INPUT OFFSET CURRENT (IOS) Initial Offset vs Temperature vs Power Supplies vs Time POWER SUPPLIES Input Stage Voltage (rated performance) Voltage (derated performance) Supply Current Output Stage Voltage (rated performance) Voltage (derated performance) Supply Current Short Circuit Current Limit CONDITIONS MIN TYP 1 0.05 0.1 100 MAX 10 MIN ISO100BP TYP T T T T MAX T MIN ISO100CP TYP T T T T MAX T UNITS nA nA/C nA/V pA/kHr IIN = -0.02 A IIN = -20A 7 18 1.1 2 +8, -1.1 +13, -2 15 1.1 15 T T T T T 18 2 40 T T T T T T T T T T T T T T T T T T T T T V V mA mA V V mA mA 7 VO = 0 BIPOLAR OPERATION GENERAL PARAMETERS Input Current Range Linear Operation Without Damage Input Impedance Output Voltage Swing Output Impedance GAIN Initial Error (Adjustable To Zero) vs Temperature vs Time Nonlinearity(3) CURRENT NOISE 0.01Hz to 10Hz 10Hz 100Hz 1kHz INPUT OFFSET CURRENT (IOS, bipolar(4)) Initial Offset vs Temperature vs Power Supplies vs Time POWER SUPPLIES Input Stage Voltage (rated performance) Voltage (derated performance) Supply Current Output Stage Voltage (rated performance) Voltage (derated performance) Supply Current Short Circuit Current Limit -10 -1 0.1 RL = 2k, RF = 1M VO = RF (IIN) 2 0.03 0.05 0.1 IIN = 0.2A 1.5 17 7 6 40 -10 1200 +10 +1 +10 T T T T T T T T T T T T T T T T A mA V % of FS %/C %/kHr % nA, p-p pA/Hz pA/Hz pA/Hz 5 0.07 0.4 1 0.01 T 0.03 T T T T 2 0.05 0.1 1 0.005 T 0.02 T T T T 2 0.03 0.07 200 3 0.7 20 70 2 T 10 35 1 T 250 T T nA nA/C nA/V pA/kHr 7 IIN = +10A IIN = -10A 7 VO = 0 18 +2, -1.1 +3, -2 +8, -1.1 +13, -2 15 1.1 15 T T T T T 18 2 40 T T T T T T T T T T T T T T T T T T T T T V V mA mA V V mA mA T Same as ISO100AP. NOTES: (1) See Typical Performance Curves for temperature effects. (2) See Theory of Operation section for definitions. For dB see Ex. 2, CM and HV errors. (3) Nonlinearity is the peak deviation from a "best fit" straight line expressed as a percent of full scale output. (4) Bipolar offset current includes effects of reference current mismatch and unipolar offset current. 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 ISO100 PIN CONFIGURATION Bottom View ISO100 Input Common 18 -In 17 Ref1 16 +In 15 Bal 14 Bal 13 -VCCA1 12 NC (1) ABSOLUTE MAXIMUM RATINGS Supply Voltages ................................................................................. 18V Isolation Voltage, AC pk or DC ......................................................... 750V Input Current ..................................................................................... 1mA Storage Temperature Range ......................................... -40C to +100C Lead Temperature (soldering, 10s) ............................................... +300C Output Short-Circuit Duration ................................ Continuous to Ground 1 2 3 4 A1 A2 5 6 7 8 9 NC(1) +VCCA2 VOUT -VCCA2 Bal Bal RF Ref2 Output Common PACKAGE INFORMATION PRODUCT ISO100AP ISO100BP ISO100CP PACKAGE 18-Pin Bottom-Braze DIP 18-Pin Bottom-Braze DIP 18-Pin Bottom-Braze DIP PACKAGE DRAWING NUMBER(1) 220 220 220 11 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. +VCCA1 10 NOTE: (1) No internal connection. ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with USA OEM PRICES appropriate precautions. Failure to observe proper handling 1-24 25-99 100+ and installation procedures can cause damage. ESD damage can range45.02 subtle performance degradafrom 57.94 36.22 64.62 51.69 42.48 tion 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. $53.18 $40.94 $32.21 ORDERING INFORMATION PRODUCT ISO100AP ISO100BP ISO100CP PACKAGE 18-Pin Bottom-Braze DIP 18-Pin Bottom-Braze DIP 18-Pin Bottom-Braze DIP TEMPERATURE RANGE -25C to +85C -25C to +85C -25C to +85C ISO100 4 TYPICAL PERFORMANCE CURVES At TA = +25C, VCC = 15VDC, unless otherwise specified. SMALL SIGNAL FREQUENCY RESPONSE 20 10 No CF 0 -10 CF = 4pF -20 -30 -40 1 10 100 Frequency (kHz) 1000 0 10k Output Swing (V) BIPOLAR OUTPUT SWING vs RF 20 18VCC 15 13VCC 10 Output Stage Power Supply 5 VO = (12A) (RF) = |VCC| - 1.2V max 100k 1M RF () 10M 100M 10VCC 7VCC Amplitude (dB) BIPOLAR INPUT STAGE SUPPLY CURRENT vs INPUT CURRENT 10 PHASE SHIFT vs FREQUENCY 0 No CF Supply Current (mA) 5 +VCC 0 -VCC -5 90 Phase (degrees) 180 CF = 4pF 270 -10 -20 -10 0 IIN (A) 10 20 1 10 100 Frequency (kHz) 1000 UNIPOLAR OUTPUT SWING vs RF 0 VO = (12A) (RF) = |VCC| - 1.2 V max 10 UNIPOLAR INPUT STAGE SUPPLY CURRENT vs INPUT CURRENT Not specified for operation in this region. 10VCC -10 Output Stage Power Supply 13VCC Supply Current (mA) -5 Output Swing (V) 7VCC 5 +VCC 0 -VCC -5 -30 Short circuit current limit. -15 18VCC -20 10k 100k 1M RF () 10M 100M -20 -10 0 IIN (A) 10 20 5 ISO100 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VCC = 15VDC, unless otherwise specified. ISOLATION LEAKAGE CURRENT vs ISOLATION VOLTAGE 3 AC Leakage Current (Arms) CONTINUOUS DC ISOLATION VOLTAGE vs TEMPERATURE 15 Continuous DC Isolation Voltage (V) 1250 DC Leakage Current (nA) 1000 2 10 750 Recommended Operating Region 65C 250 85C 0 -25 0 25 50 75 100 125 Temperature (C) 1 Max at 60Hz Typ at 60Hz Typ at DC 5 500 0 0 1 2 3 Isolation Voltage (kV) 0 AC ISOLATION VOLTAGE vs TEMPERATURE 1250 Rate of Change of Gain Error (%/hr) 1.5 RATE OF GAIN ERROR SHIFT vs ISOLATION VOLTAGE Short term shift (10 hrs) 1 Long term shift is random. 0.5 Temp = up to +65C Temp = +85C AC Isolation Voltage (Vp) 1000 750 Recommended Operating Region 500 250 85C 0 -25 0 25 50 100 125 Temperature (C) 0 0 250 500 750 1000 Isolation Voltage (VDC) GAIN ERROR vs TEMPERATURE AND ISOLATION VOLTAGE 3 Gain Error (Normalized to +25C) 2.5 2 1.5 1 0.5 0 -25 0 25 50 65 75 TT 100 125 VIM >VT VIM < VT Temperature (C) NOTES: VT and TT approximate the threshold for the indicated gain shift. This is caused by the properties of the optical cavity. TT +65C, VT 200VDC. Shift does not occur fo AC voltages. VIM = Isolation-Mode Voltage VT = Threshold Voltage TT = Threshold Temperature ISO100 6 THEORY OF OPERATION The ISO100 is fundamentally a unity gain current amplifier intended to transfer small signals between electrical circuits separated by high voltages or different references. In most applications, an output voltage is obtained by passing the output current through the feedback resistor (RF). The ISO100 uses a single light emitting diode (LED) and a pair of photodiode detectors coupled together to isolate the output signal from the input. Figure 1 shows a simplified diagram of the amplifier. IREF1 and IREF2 are required only for bipolar operation to generate a midscale reference. The LED and photodiodes (D1 and D2) are arranged such that the same amount of light falls on each photodiode. Thus, the currents generated by the diodes match very closely. As a result, the transfer function depends upon optical match rather than absolute performance. Laser-trimming of the components improves matching and enhances accuracy, while negative feedback improves linearity. Negative feedback around A1 occurs through the optical path formed by the LED and D1. The signal is transferred across the isolation barrier by the matched light path to D2. The overall isolation amplifier is noninverting (a positive going input produces a positive going output). the LED. As the LED light output increases, D1 responds by generating an increasing current. The current increases until the sum of the currents in and out of the input node (-Input to A1) is zero. At that point, the negative feedback through D1 has stabilized the loop, and the current ID1 equals the input current plus the bias current. As a result, no bias current flows in the source. Since D1 and D2 are matched (ID1 = ID2), IIN is replicated at the output via D2. Thus, A1 functions as a unity-gain current amplifier, and A2 is a current-to-voltage converter, as described below. Current produced by D2 must either flow into A2 or RF. Since A2 is designed for low bias current (10nA), almost all of the current flows through RF to the output. The output voltage then becomes: VO = (ID2)RF = (ID1 IOS)RF -(-IIN)RF = IINRF (1) where, IOS is the difference between A1 and A2 bias currents. For input voltage operation IIN can be replaced by a voltage source (VIN) and series resistor (RIN), since the summing node of the op amp is essentially at ground. Thus, IIN = VIN/RIN. Unipolar operation does have some constraints, however. In this mode the input current must be negative so as to produce a positive output voltage from A1 to turn the LED on. A current more negative than 20nA is necessary to keep the LED turned on and the loop stabilized. When this condition is not met, the output may be indeterminant. Many sensors generate unidirectional signals, e.g., photoconductive and photodiode devices, as well as some applications of thermocouples. However, other applications do require bipolar operation of the ISO100. BIPOLAR OPERATION To activate the bipolar mode, reference currents as shown in Figure 1 are attached to the input nodes of the op amps. The input stage stabilizes just as it did in unipolar operation. RF INSTALLATION AND OPERATING INSTRUCTIONS UNIPOLAR OPERATION In Figure 1, assume a current, IIN, flows out of the ISO100 (IIN must be negative in unipolar operation). This causes the voltage at pin 15 to decrease. Because the amplifier is inverting, the output of A1 increases, driving current through IREF1 16 Input Circuit Isolation Barrier 7 IREF2 8 Output Circuit RIN +In 15 A1 A2 3 VOUT + VIN - -In 17 18 Input Common Connect pins 15 and 16 for bipolar, and pins 16 and 17 for unipolar. IIN Optical Assembly D1 LED D2 VOUT = IIN RF 9 Output Common Connect pins 7 and 8 for bipolar, and pins 8 and 9 for unipolar. FIGURE 1. Simplified Block Diagram of the ISO100. 7 ISO100 Assuming IIN = 0, the photodiode has to supply all the IREF1 current. Again, due to symmetry, ID1 = ID2. Since the two references are matched, the current generated by D2 will equal IREF2. This results in no current flow in RF, and the output voltage will be zero. When IIN either adds or subtracts current from the input node, the current D1 will adjust to satisfy ID1 = IIN + IREF1. Because IREF1 equals IREF2 and ID1 equals ID2, a current equal to IIN will flow in RF. The output voltage is then VO = IINRF. The range of allowable IIN is limited. Positive IIN can be as large as IREF1 (10.5A, min). At this point, D1 supplies no current and the loop opens. Negative IIN can be as large as that generated by D1 with maximum LED output (recommended 10A, max). DC ERRORS Errors in the ISO100 take the form of offset currents and voltages plus their drifts with temperature. These are shown in Figure 2. A1 and A2-- assumed to be ideal amplifiers. VOSO and VOSI--the input offset voltages of the output and input stage, respectively. VOSO appears directly at the output, but, VOSI appears at the output as VOSI see equation (2). IOS--the offset current. This is the current at the input necessary to make the output zero. It is equal to the combined effect of the difference between the bias currents of A1 and A2 and the matching errors in the optical components in the unipolar mode. I REF1 and I REF2 --reference currents that, when connected to the inputs, enable bipolar operation. The two currents are trimmed, in the bipolar mode, to minimize the IOS BIPOLAR error. ID1 and ID2--currents generated by each photodiode in response to the light from the LED. Ae--gain error. Ae = | Ideal gain/Actual gain | - 1 RF RIN , (1) The output then becomes: VOSO VOUT = RF[( VIN VOS RIN - IREF1 IOS)(1 + Ae)+ IREF2] (2) The total input referred offset voltage of the ISO100 can be simplified in the unipolar case by assuming that Ae = 0 and VIN = 0: VOUT RF [ VOSI RIN IOS UNIPOLAR ] VOSO (3) This voltage is then referred back to the input by dividing by RF/RIN. VOS (RTI) = (VOSI) RIN (IOS (4) UNIPOLAR) + VOSO/(RF/RIN) Example 1. Refer to Figure 2 and Electrical Specifications Table. Given: IOS BIPOLAR RIN = 100k RF = 1M (gain = 10) VOSI = +200V VOSO = +200V = +35nA Find: The total offset voltage error referred to the input and output when VIN = 0V. VOS total RTI = {[VOSI RIN (IOS BIPOLAR) - RIN (IREF 1)] [1 + Ae] + RIN IREF 2} VOSO/(RF/RIN) = {[+200V + 100k (35nA) - 100k (12.5A)] [1.02] + 100k (12.5A]} + 200V/(1M/100k) = {[0.2mV + 3.5mV - 1.25V] [1.02] + 1.25V} + 0.02mV = -21.2mV VOS total RTO = VOS total RTI x RF/RIN = -21.2mV x 10 = -212mV VOSI RIN + + - VOSO ISO100 Isolation Barrier A1 + - RF(1) A2 LED IREF2 ID2 VOUT VIN - IREF1 ID1 IOS NOTE: (1) Use 1M or greater to achieve a full scale output of 10V. FIGURE 2. Circuit Model for DC Errors in the ISO100. ISO100 8 NOTE: This error is dominated by IOS BIPOLAR and the reference current times the gain error (which appears as an offset). The error for unipolar operation is much lower. The error due to offset current can be zeroed using circuits shown in Figures 6 and 7. The gain error is adjusted by trimming either RF or RIN. COMMON-MODE AND HIGH VOLTAGE ERRORS Figure 3 shows a model of the ISO100 that can be used to analyze common-mode and high voltage behavior. VERR is the equivalent error signal, applied in series with the input voltage, which produces an output error identical to that produced by application of VCM and VIM. CMRR and IMRR are the common-mode and isolationmode rejection ratios, respectively. Total Capacitance (C1 and C2) is distributed along the isolation barrier. Most of the capacitance is coupled to low impedance or noncritical nodes and affects only the leakage current. Only a small capacitance (C2) couples to the input of the second stage, and contributes to IMRR. Example 2. Refer to Figure 3 and Electrical Specification Table. Given: VCM = 1VAC peak at 60Hz, VIM = 200VDC, CMRR = 3nA/V, IMRR = 5pA/V, RIN = 100k, RF = 1M (Gain = 10) Isolation Barrier RF RIN + VIN - + VERR CM + - + VCM + Input Common VIM C1 - Output Common - VERR IM + - VOUT - C2 Find: The error voltage referred to the input and output when VIN = 0V VERR RTI= (VCM)(CMRR)(RIN) + (VIM)(IMRR)(RIN) = 1V (3nA/V)(100k) + 200V (5pA/V)(100k) = 0.3mV + 0.1mV = 0.4mV VERR RTO = VERR RTI (RF/RIN) FIGURE 3. High Voltage Error Model. Definitions of CMR and IMR IOS is defined as the input current required to make the ISO100's output zero. CMRR and IMRR in the ISO100 are expressed as conductances. CMRR defines the relationship between a change in the applied common-mode voltage (VCM) and the change in IOS required to maintain the amplifier's output at zero: CMRR (I-mode) = IOS/VCM in nA/V CMRR (V-mode) = IOS VCM RIN = VERR CM VCM (5) in V/V (6) = 0.4mV (10) =4mV (with DC IMRR) NOTE: This error is dominated by the CMRR term. For purposes of comparing CMRR and IMRR directly with dB specifications, the following calculations can be performed: CMRR in V/V = CMRR (I-mode)(RIN) = 3nA/V (100k) = 0.3mV/V CMR = 20 LOG (0.3mV/V) = -70dB at 60Hz IMRR in V/V = IMRR (I-mode)(RIN) = 5pA/V(100k) = 0.5V/V IMR = 20 LOG (0.5 x 10-6V/V) = -126dB at DC Example 3. In Example 3, VIM is an AC signal at 60Hz and IMRR = 400pA V IMRR defines the relationship between a change in the applied isolation mode voltage (VIM) and the change in IOS required to maintain the amplifier's output to zero: IMRR (I-mode) = IOS VIM in pA/V VERR IM VIM (7) IMRR (V-mode) = IOS VIM RIN = in V/V (8) CMRR and IMRR in V/V are a function of RIN. VIM is the voltage between input common and output common. VCM is the common-mode voltage (noise that is present on both input lines, typically 60Hz). VERR RTI = VERR CM + VERR IM = 0.3mV + 200V (400pA/V)(100k) = 8.3mV VERR RTO = 83mV (with AC IMRR) 9 ISO100 Example 4. Given: Total error RTO from Examples 1 and 3 as 378mV worst case. Find: Percent error of +10V full scale output % Error = = VERR TOTAL VFS x 100% 378mV x 100% 10V = 3.78% NOISE ERRORS Noise errors in the unipolar mode are due primarily to the optical cavity. When the full 60kHz bandwidth is not needed, the output noise of the ISO100 can be limited by either a capacitor, CF, in the feedback loop or by a low-pass filter following the output. This is shown in Figure 4. Noise in the bipolar mode is due primarily to the reference current sources, and can be reduced by the low-pass filters shown in Figure 5. OPTIONAL ADJUSTMENTS There are two major sources of offset error: offset voltage and offset current. VOSI and VOSO of the input and output amplifiers can be adjusted independently using external potentiometers. An example is shown in Figure 17. Note that VOSO (500V, max) appears directly at the output, but VOSI appears at the output multiplied by gain (RF/RIN). In general, VOS is small compared to the effect of IOS (see Example 1). To adjust for IOS use a circuit which intentionally unbalances the offset in one direction and then allows for adjustment back to zero. Figure 6 shows how to adjust unipolar errors at zero input. The unipolar amplifier can be used down to zero input if it is made to be "slightly bipolar." By sampling the reference current with R5 and R6, the minimum current required to keep the input stage in the linear region of operation can be established. R7 and R8 are adjusted to cancel the offset created in the input stage. This brings the output to zero, when the input is zero. Although the amplifier can now operate down to zero input voltage, it has only a small portion of the current drain and noise that the true bipolar configuration would have. Adjusting the bipolar errors is illustrated in Figure 7. Each of the errors are adjusted in turn. With VIN = "open,", IOS is trimmed by adjusting R10 to make the output zero. RG is then adjusted to trim the gain error. The effects of offset voltage are removed by adjusting R14. Optional Unipolar IOS Adjust. CF 15 RF 7 IIN ISO100 9 3 R fO = 1 2RFCF 1 fO = 2RC C 17 18 R6 84k R7 10M IC2 ISO100 RF 1M R8 200k Pot R5 10M IIN IC1 +In IREF 1 FIGURE 4. Two Circuit Techniques for Reducing Noise in the Unipolar Mode. 1M RF IREF 2 VOUT 100k 1F 100k 15 16 1F IC2 (MAX) IC2 (MIN) 3 9 VOUT Shift due to R7 and R8. Shift due to R5 and R6. ea l -In 18 VOUT 7 IIN ISO100 8 IIN 18 FIGURE 5. Circuit Techniques for Reducing Noise from the Current Sources in the Bipolar Mode. FIGURE 6. Adjusting the Unipolar Amplifier Errors at Zero Input. 10 ISO100 Id 17 R10 1M R11 10M Optional Bipolar IOS Adjust. RF 1M R1 15 + 16 RF RIN VIN 9.76k RG 500 Pot 15 +In ISO100 9 + 7 - IC R12 316k R13 10M 7 ISO100 9 8 3 8 3 VOUT + RSOURCE - 17 VOUT = -VIN (RF /R1) 18 VIN(1) -In 17 13 18 R14 100k 14 +V NOTE: (1) Use postitive input voltage only, VIN >> 10A x RSOURCE. FIGURE 10. Unipolar Inverting. FIGURE 7. Adjusting the Bipolar Errors. R1 15 + 16 RF BASIC CIRCUIT CONNECTIONS 7 ISO100 9 RSOURCE + VIN(1) 8 3 - 17 18 VOUT = -VIN (RF /R1) NOTE: (1) VIN >> 10A x RSOURCE. FIGURE 11. Bipolar Inverting. APPLICATION INFORMATION FIGURE 8. Unipolar Noninverting. The small size, low offset and drift, wide bandwidth, ultralow leakage, and low cost, make the ISO100 ideal for a variety of isolation applications. The basic mode of operation of the ISO100 will be determined by the type of signal and application. Major points to consider when designing circuits with the ISO100. 3 9 VOUT = IINRF or VOUT = VIN (RF /RIN) 18 RIN Shield 15 + 16 RF + ISO100 VIN IIN - 17 7 8 1. Input Common (pin 18) and -In (pin 17) should be grounded through separate lines. The Input Common can carry a large DC current and may cause feedback to the signal input. 2. Use shielded or twisted pair cable at the input for long lines. 3. Care should be taken to minimize external capacitance across the isolation barrier. FIGURE 9. Bipolar Noninverting. 11 ISO100 4. The distance across the isolation barrier, between external components and conductor patterns, should be maximized to reduce leakage and arcing. 5. Although not an absolute requirement, the use of conformally-coated printed circuit boards is recommended. 6. When in the unipolar mode, the reference currents (pins 8 and 16) must be terminated. IIN should be greater than 20nA to keep internal LED on. 7. The noise contribution of the reference currents will cause the bipolar mode to be noisier than the unipolar mode. 8. The maximum output voltage swing is determined by IIN and RF. VSWING = IIN MAX X RF 9. A capacitor (about 3pF) can be connected across RF to compensate for peaking in the frequency response. The peaking is caused by the pole generated by RF and the capacitance at the input of the output amplifier. Figure 12 through 18 show applications of the ISO100. 0.02A to 10A 15 + CF may be used to improve frequency response (reduce peaking). Isolation Barrier fO = 1/2 RFCF CF 16 RF 1M Photodiode 7 ISO100 9 8 3 2 4 C2 0.001F VO = IINRF 0 to -10V - 17 10 18 R3 15k +V C 722 Isolated Power Supply -V C 12 C3 0.001F R2 15k -V +V p+ V+ E V- R1 1.2k +15V C1 0.47F R3 and R2 are required to maintain a 3mA minimum load to the 722. FIGURE 12. Two-Port Isolation Photodiode Amplifier Unipolar. R2 50k R3 50k Bridge Excitation Sensor Tranducer R R VREF = +1V 6 - 2 IREF 1 (2) CF RF 1M 16 15 + OPA177 3 + 10 1 VIN RG 404 4 5 + (3) R R INA101 X 100 - 6 9 8 7 R1 100k 7 ISO100 X 10 9 - 8 + 4 2 +15V -15V VOUT - 17 12 18 Total Gain = 1000 Input Common Output Common 10 (1) +15V -15V NOTES: (1) For isolated supplies see Figure 12. (2) In this example, the internal precision current reference, IREF, provides bridge excitation. (3) Pin 8 of the INA101 must be more negative than -2mV for linear operation of the ISO100 with R1 = 100k. FIGURE 13. Precision Bridge Isolation Amplifier (Unipolar). ISO100 12 CF may be used to improve frequency response (reduce peaking). Isolation Barrier fO = 1/2 RFCF Offsetting CF R4 1k 16 15 + 7 RF 1M R4 100k -15V Gain Adjust R3 2M R2 1k VO = IINRF (10V) +15V CF RF 1M 8 3 2 4 C2 0.001F V = 10mV (Temp) ISO100 9 Thermocouple - 17 10 18 R3 15k +V C 722 -V C 12 C3 0.001F R1 100k + VIN 15 + 16 7 ISO100 9 8 3 R2 15k VOUT - 17 +V p+ V+ E V- R1 1.2k +15V 18 -V Gain = +10 to +1000 C1 0.47F Cold junction compensation not shown. Isolated Power Supply Approximate input offsetting = 0 to 7.5A for isolated supplies--see Figures 10 and 11. R3 and R2 are required to maintain a 3mA minimum load to the 722. FIGURE 14. Three-Port Isolation Thermocouple Amplifier (Bipolar). FIGURE 15. Isolated Test Equipment Amplifier (Unipolar with Offsetting). R1 1M R2 500k Input -5V to 0V RIN 500 Span Adjust ISO100 16 15 + Offset Adjust +VISOLATED IOUT 4-20mA 3 Siliconix VN88AF R4 335k 7 - 8 2 RL 9 + 4 - 17 18 -VISOLATED R3 200 For isolated supplies see Figures 10 and 11. Calibration procedure: 1. Set VIN = 0V 2. Adjust R2 for IOUT = 20mA 3. Set VIN = -5V 4. Adjust RIN for IOUT = 4mA FIGURE 16. Isolated 4mA to 20mA Transmitter (Example of an isolated voltage controlled current source). 13 ISO100 +VCC 1M RIN 10k VIN 1 13 15 + Offset Adjust RF 1M +15V 14 7 9 5 - + 2 1M Offset Adjust 63 4 VOUT - Com 1 17 +15V -15V (Non ISO) +VCC 100k VIN 2 15 + 7 9 - Com 2 17 - (1) -VCC VO = 1M [ VIN 2 VIN 1 + + IIN 1 +IIN 2] 10k 100k + +VCC IIN 1 15 + -VCC 7 9 - Com 3 17 - (1) + +VCC IIN 2 15 + -VCC 1 VCCs to input stages of amplifiers 2 3 4 7 9 - Com 4 17 - (1) + 724 Isolated Power Supply +VCC -VCC NOTE: (1) No additional connections to output amplifiers Note that a variety of input/gain configurations can be used. +15V (Non ISO) FIGURE 17. Four-Port Isolated Summing Amplifier (Unipolar). ISO100 14 Channel Select OPTO Isolator Gain Select CP CE IN7 IN6 IN5 Input Channels IN4 IN3 IN2 IN1 IN0 Digital P/S ISO100 9 2 - 17 10 +5V +15V Input Common(1) -15V Output Common(1) +15V -15V NOTE: (1) For isolated power supplies see Figures 10 and 11. 12 18 4 VOUT PGA100 Analog P/S 1M 15 + 7 8 3 16 RF 1M CF FIGURE 18. Multiple Channel Isolation Amplifier (Bipolar) with Programmable Gain (useful in data acquisition systems). 15 ISO100 WWW..COM Copyright (c) Each Manufacturing Company. All Datasheets cannot be modified without permission. This datasheet has been download from : www..com 100% Free DataSheet Search Site. Free Download. No Register. Fast Search System. www..com |
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