IL300 LINEAR OPTOCOUPLER FEATURES • Couples AC and DC signals • 0.01% Servo Linearity • Wide Bandwidth, >200 KHz • High Gain Stability, ±0.005%/C • Low Input-Output Capacitance • Low Power Consumption, < 15mw • Isolation Test Voltage, 5300 VACRMS, 1 sec. • Internal Insulation Distance, >0.4 mm for VDE • Underwriters Lab File #E52744 • VDE Approval #0884 (Optional with Option 1, Add -X001 Suffix) • IL300G Replaced by IL300-X006 APPLICATIONS • Power Supply Feedback Voltage/ Current • Medical Sensor Isolation • Audio Signal Interfacing • Isolate Process Control Transducers • Digital Telephone Isolation DESCRIPTION The IL300 Linear Optocoupler consists of an AlGaAs IRLED irradiating an isolated feedback and an output PIN photodiode in a bifurcated arrangement. The feedback photodiode captures a percentage of the LED's flux and generates a control signal (IP1) that can be used to servo the LED drive current. This technique compensates for the LED's non-linear, time, and temperature characteristics. The output PIN photodiode produces an output signal (IP2) that is linearly related to the servo optical flux created by the LED. The time and temperature stability of the input-output coupler gain (K3) is insured by using matched PIN photodiodes that accurately track the output flux of the LED. A typical application circuit (Figure 1) uses an operational amplifier at the circuit input to drive the LED. The feedback photodiode sources current to R1 connected to the inverting input of U1. The photocurrent, IP1, will be of a magnitude to satisfy the relationship of (IP1=VIN /R1). Dimensions in inches (mm) 4 3 2 1 Pin One I.D. 8 1 .268 (6.81) .255 (6.48) 2 5 6 7 8 K1 K2 7 3 6 4 5 .390 (9.91) .379 (9.63) .305 Typ. (7.75) Typ. .045 (1.14) .150 (3.81) .030 (.76) .130 (3.30) .135 (3.43) .115 (2.92) 4° Typ. 10 ° Typ. .040 (1.02) .030 (.76 ) .100 (2.54) Typ. .022 (.56) .018 (.46) 3°–9° .012 (.30) .008 (.20) DESCRIPTION (continued) The magnitude of this current is directly proportional to the feedback transfer gain (K1) times the LED drive current (VIN /R1=K1 • IF). The op-amp will supply LED current to force sufficient photocurrent to keep the node voltage (Vb) equal to Va The output photodiode is connected to a non-inverting voltage follower amplifier. The photodiode load resistor, R2, performs the current to voltage conversion. The output amplifier voltage is the product of the output forward gain (K2) times the LED current and photodiode load, R2 (VO=IF • K2 • R2). Therefore, the overall transfer gain (VO/VIN) becomes the ratio of the product of the output forward gain (K2) times the photodiode load resistor (R2) to the product of the feedback transfer gain (K1) times the input resistor (R1). This reduces to VO/VIN= (K2 • R2)/(K1 • R1). The overall transfer gain is completely independent of the LED forward current. The IL300 transfer gain (K3) is expressed as the ratio of the ouput gain (K2) to the feedback gain (K1). This shows that the circuit gain becomes the product of the IL300 transfer gain times the ratio of the output to input resistors [VO/ VIN=K3 (R2/R1)]. Figure 1. Typical application circuit Va + Vin 2 U1 Vb IL300 1 8 VCC + - K1 IF VCC 3 R1 5–1 7 6 VCC - VCC U2 4 lp 1 K2 5 lp 2 Vc R2 + Vout IL300 Terms Absolute Maximum Ratings KI—Servo Gain Symbol Min. Max. Unit 160 mW 2.13 mW/°C The ratio of the input photodiode current (IP1) to the LED current(IF). i.e., K1 = IP1/ IF. Emitter K2—Forward Gain Power Dissipation (TA=25°C) The ratio of the output photodiode current ( IP2) to the LED current (IF), i.e., K2 = IP2/ IF. Derate Linearly from 25°C K3—Transfer Gain Forward Current lf 60 mA The Transfer Gain is the ratio of the Forward Gain to the Servo gain, i.e., K3 = K2/K1. Surge Current (Pulse width <10µs) lpk 250 mA ∆K3—Transfer Gain Linearity Reverse Voltage VR 5 V Thermal Resistance Rth 470 °C/W Junction Temperature TJ 100 °C PDET 50 mA 0.65 mW/°C The percent deviation of the Transfer Gain, as a function of LED or temperature from a specific Transfer Gain at a fixed LED current and temperature. Photodiode PLED Detector A silicon diode operating as a current source. The output current is proportional to the incident optical flux supplied by the LED emitter. The diode is operated in the photovoltaic or photoconductive mode. In the photovoltaic mode the diode functions as a current source in parallel with a forward biased silicon diode. Power Dissipation Derate linearly from 25°C The magnitude of the output current and voltage is dependant upon the load resistor and the incident LED optical flux. When operated in the photoconductive mode the diode is connected to a bias supply which reverse biases the silicon diode. The magnitude of the output current is directly proportional to the LED incident optical flux. Reverse Voltage VR 50 V Junction Temperature TJ 100 °C Thermal Resistance Rth 1500 °C/W PT 210 mW 2.8 mW/°C Coupler Total Package Dissipation at 25°C LED (Light Emitting Diode) Derate linearly from 25°C An infrared emitter constructed of AlGaAs that emits at 890 nm operates efficiently with drive current from 500 µA to 40 mA. Best linearity can be obtained at drive currents between 5 mA to 20 mA. Its output flux typically changes by –0.5%/°C over the above operational current range. Storage Temperature TS –55 150 °C Operating Temperature TOP –55 100 °C Isolation Test Voltage 5300 VACRMS Isolation Resistance VIO=500 V, TA=25°C VIO=500 V, TA=100°C 1012 1011 Ω Ω IL300 5–2 Characteristics (TA=25°C) Symbol Min. Typ. Max. Unit Test Condition 1.50 V IF=10 mA LED Emitter Forward Voltage VF 1.25 VF Temperature Coefficient ∆VF/∆°C -2.2 Reverse Current IR 1 Junction Capacitance CJ Dynamic Resistance Switching Time mV/°C µA VR=5 V 15 pF VF=0 V, f=1 MHz ∆VF/∆IF 6 Ω IF=10 mA tR tF 1 1 µs µs ∆IF=2 mA, IFq=10 mA ∆IF=2 mA, IFq=10 mA Dark Current ID 1 nA Vdet=-15 V, IF=0 µA Open Circuit Voltage VD 500 mV IF=10 mA Short Circuit Current ISC 70 µA IF=10 mA Junction Capacitance CJ 12 pF VF=0 V, f=1 MHz NEP 4 x 1014 W/√Hz Vdet=15 V 10 Detector Noise Equivalent Power 25 Coupled Characteristics K1, Servo Gain (IP1/IF) K1 Servo Current, see Note 1, 2 IP1 K2, Forward Gain (IP2/IF) K2 Forward Current IP2 K3, Transfer Gain (K2/K1) See Note 1, 2 K3 Transfer Gain Linearity ∆K3 Transfer Gain Linearity 0.0050 0.007 0.011 µA 70 0.0036 IF=10 mA, Vdet=-15 V 0.007 0.011 IF=10 mA, Vdet=-15 V IF=10 mA, Vdet=-15 V µA IF=10 mA, Vdet=-15 V K2/K1 IF=10 mA, Vdet=-15 V ±0.25 % IF=1 to 10 mA ∆K3 ±0.5 % IF=1 to 10 mA, TA=0°C to 75°C BW (-3 db) 200 KHz IFq=10 mA, MOD=±4 mA, RL=50 Ω, -45 Deg. Vdet=-15 V 70 0.56 1.00 1.65 Photoconductive Operation Frequency Response Phase Response at 200 KHz Rise Time tR 1.75 µs Fall Time tF 1.75 µs Input-Output Capacitance CIO 1 pF VF=0 V, f=1 MHz Common Mode Capacitance Ccm 0.5 pF VF=0 V, f=1 MHz Common Mode Rejection Ratio CMRR 130 dB f=60 Hz, RL=2.2 KΩ Package 2. Bin Categories: All IL300s are sorted into a K3 bin, indicated by an alpha character that is marked on the part. The bins range from “A” through “J”. The IL300 is shipped in tubes of 50 each. Each tube contains only one category of K3. The category of the parts in the tube is marked on the tube label as well as on each individual part. 3. Category Options: Standard IL300 orders will be shipped from the categories that are available at the time of the order. Any of the ten categories may be shipped. For customers requiring a narrower selection of bins, four different bin option parts are offered. IL300-DEFG: Order this part number to receive categories D,E,F,G only. IL300-EF: Order this part number to receive categories E, F only. IL300-E: Order this part number to receive category E only. IL300-F: Order this part number to receive category F only Notes 1. Bin Sorting: K3 (transfer gain) is sorted into bins that are ±5%, as follows: Bin A=0.557–0.626 Bin B=0.620–0.696 Bin C=0.690–0.773 Bin D=0.765–0.859 Bin E=0.851–0.955 Bin F=0.945–1.061 Bin G=1.051–1.181 Bin H=1.169–1.311 Bin I=1.297–1.456 Bin J=1.442–1.618 K3=K2/K1. K3 is tested at IF=10 mA, Vdet=–15 V. IL300 5–3 Figure 6. Normalized servo photocurrent vs. LED current and temperature Figure 2. LED forward current vs. forward voltage 35 3.0 Normalized Photocurrent IF - LED Current - mA 30 25 20 15 10 5 0 1.0 Normalized to:IP1 @ IF=10 mA, TA=25°C, 0°C V =–15 V D 2.5 25°C 50°C 75°C 2.0 1.5 1.0 0.5 0.0 1.1 1.2 1.3 0 1.4 Figure 3. LED forward current vs. forward voltage IP1- Normalized Photocurrent IF - LED Current - mA 10 10 1 1.1 1.2 1.3 VF - LED Forward Voltage - V 1.4 NK1- Normalized Servo Gain IP1- Servo Photocurrent - µA 200 VD=–15 V 150 100 50 0 .1 1 10 TA=25°C, VD=–15 V 1 0°C 25°C 50°C 75°C .1 .01 .1 100 0° 25° 1.0 50° 75° 85° 0.8 0.6 0.4 0.2 1 10 100 Figure 9. Normalized servo gain vs. LED current and temperature 1.2 VD=–15 V Vd = -15V NK1- Normalized Servo Gain IP1- Servo Photocureent - µA 10 IF - LED Current - mA 1000 10 1 .1 1 1.2 0.0 .1 100 Figure 5. Servo photocurrent vs. LED current and temperatureFigure LED current and temperature 100 25 Normalized to IP1 @ IF=10 mA, IF - LED Current - mA 0°C 25°C 50°C 75°C 20 Figure 8. Servo gain vs. LED current and temperature 300 250 15 IF - LED Current - mA Figure 4. Servo photocurrent vs. LED current and temperature 0°C 25°C 50°C 75°C 10 Figure 7. Normalized servo photocurrent vs. LED current and temperature 100 .1 1.0 5 IF - LED Current - mA VF - LED Forward Voltage - V 0° 25° 1.0 50° 75° 0.8 100° 0.6 0.4 Normalized to: IF=10 mA, TA=25°C 0.2 0.0 1 10 IF - LED Current - mA .1 100 1 10 IF - LED Current - mA 100 IL300 5–4 Figure 14. Common mode rejection Figure 10. Transfer gain vs. LED current and temperature -60 K3 - Transfer Gain - (K2/K1) 1.010 CMRR - Rejection Ratio - dB 0°C 1.005 25°C 1.000 50°C 75°C 0.995 5 10 15 20 -80 -90 -100 -110 -120 -130 10 0.990 0 -70 25 100 IF - LED Current - mA 10000 100000 1000000 Figure 15. Photodiode junction capacitance vs. reverse voltage Figure 11. Normalized transfer gain vs. LED current and temperature 14 1.010 Normalized to IF=10 mA, TA=25°C 0°C K3 - Transfer Gain - (K2/K1) 1000 F - Frequency - Hz 12 Capacitance - pF 1.005 25°C 1.000 50°C 75°C 0.995 10 8 6 4 2 0 0.990 0 5 10 15 20 0 25 2 4 6 8 10 Voltage - Vdet IF - LED Current - mA Application Considerations Figure 12. Amplitude response vs. frequency In applications such as monitoring the output voltage from a line powered switch mode power supply, measuring bioelectric signals, interfacing to industrial transducers, or making floating current measurements, a galvanically isolated, DC coupled interface is often essential. The IL300 can be used to construct an amplifier that will meet these needs. 5 Amplitude Response - dB IF=10 mA, Mod=± 2 mA (peak) 0 RL=1 KΩ -5 The IL300 eliminates the problems of gain nonlinearity and drift induced by time and temperature, by monitoring LED output flux. -10 RL=10 KΩ -15 -20 10 4 10 5 F - Frequency - Hz A PIN photodiode on the input side is optically coupled to the LED and produces a current directly proportional to flux falling on it . This photocurrent, when coupled to an amplifier, provides the servo signal that controls the LED drive current. 10 6 The LED flux is also coupled to an output PIN photodiode. The output photodiode current can be directly or amplified to satisfy the needs of succeeding circuits. Figure 13. Amplitude and phase response vs. frequency 45 dB PHASE 0 0 -5 -45 -10 -15 -90 IFq=10 mA Mod=± 4 mA TA=25°C RL=50 Ω -20 10 3 10 4 10 5 10 6 F - Frequency - Hz Isolated Feedback Amplifier Ø - Phase Response -° Amplitude Response - dB 5 The IL300 was designed to be the central element of DC coupled isolation amplifiers. Designing the IL300 into an amplifier that provides a feedback control signal for a line powered switch mode power is quite simple, as the following example will illustrate. See Figure 17 for the basic structure of the switch mode supply using the Siemens TDA4918 Push-Pull Switched Power Supply Control Chip. Line isolation and insulation is provided by the high frequency transformer. The voltage monitor isolation will be provided by the IL300. -135 -180 10 7 IL300 5–5 The isolated amplifier provides the PWM control signal which is derived from the output supply voltage. Figure 16 more closely shows the basic function of the amplifier. Figure 16. Isolated control amplifier + ISO AMP +1 To Control Input The control amplifier consists of a voltage divider and a noninverting unity gain stage. The TDA4918 data sheet indicates that an input to the control amplifier is a high quality operational amplifier that typically requires a +3V signal. Given this information, the amplifier circuit topology shown in Figure 18 is selected. R1 Voltage Monitor - R2 The power supply voltage is scaled by R1 and R2 so that there is +3 V at the non-inverting input (Va) of U1. This voltage is offset by the voltage developed by photocurrent flowing through R3. This photocurrent is developed by the optical flux created by current flowing through the LED. Thus as the scaled monitor voltage (Va) varies it will cause a change in the LED current necessary to satisfy the differential voltage needed across R3 at the inverting input. For best input offset compensation at U1, R2 will equal R3. The value of R1 can easily be calculated from the following. V MONITOR R1 = R2 -------------------------- – 1 V a The first step in the design procedure is to select the value of R3 given the LED quiescent current (IFq) and the servo gain (K1). For this design, IFq=12 mA. Figure 4 shows the servo photocurrent at IFq is found to be 100 µA. With this data R3 can be calculated. Vb 3V R3 = ------ = ------------------ = 30KΩ I Pl 100µA The value of R5 depends upon the IL300 Transfer Gain (K3). K3 is targeted to be a unit gain device, however to minimize the part to part Transfer Gain variation, Siemens offers K3 graded into ± 5 % bins. R5 can determined using the following equation, V OUT R3 ( R1 + R2 ) R5 = --------------------------- • ------------------------------------V R2K3 5V 20KΩ = 30KΩ -----3V- – 1 MONITOR Or if a unity gain amplifer is being designed (VMONITOR=VOUT, R1=0), the euation simplifies to: R3 R5 = -----K3Figure 17. Switch mode power supply 110/ 220 MAIN DC OUTPUT AC/DC RECTIFIER SWITCH SWITCH MODE REGULATOR TDA4918 XFORMER CONTROL AC/DC RECTIFIER ISOLATED FEEDBACK Figure 18. DC coupled power supply feedback amplifier Vmonitor R1 20 KΩ R2 30 KΩ IL300 7 3 + R4 VCC 100 Ω Va 6 U1 LM201 2 1 Vb 8 VCC 4 100 pF - 1 8 2 K2 7 K1 3 6 4 5 R3 30 KΩ VCC Vout R5 30 KΩ To control input IL300 5–6 Table 1 gives the value of R5 given the production K3 bins. Figure 20. Linearity error vs. input voltage 0.025 Table 1. R5 selection 0.020 K3 Typ. R5 Resistor KΩ 1% KΩ A 0.560 0.623 0.59 50.85 51.1 B 0.623 0.693 0.66 45.45 45.3 C 0.693 0.769 0.73 41.1 41.2 D 0.769 0.855 0.81 37.04 37.4 E 0.855 0.950 0.93 32.26 32.4 F 0.950 1.056 1.00 30.00 30.0 G 1.056 1.175 1.11 27.03 27.0 H 1.175 1.304 1.24 24.19 24.0 I 1.304 1.449 1.37 21.90 22.0 J 1.449 1.610 1.53 19.61 19.4 The last step in the design is selecting the LED current limiting resistor (R4). The output of the operational amplifier is targeted to be 50% of the Vcc, or 2.5 V. With an LED quiescent current of 12 mA the typical LED (VF ) is 1.3 V. Given this and the operational output voltage, R4 can be calculated. . V opamp – V F 2.5V – 1.3V R4 = ------------------------------- = ----------------------------I Fq 12mA - = 100Ω The circuit was constructed with an LM201 differential operational amplifier using the resistors selected. The amplifier was compensated with a 100 pF capacitor connected between pins 1 and 8. The DC transfer charateristics are shown in Figure 19. The amplifier was designed to have a gain of 0.6 and was measured to be 0.6036. Greater accurracy can be achieved by adding a balancing circuit, and potentiometer in the input divider, or at R5. The circuit shows exceptionally good gain linearity with an RMS error of only 0.0133% over the input voltage range of 4 V–6 V in a servo mode; see Figure 20. LM201 0.015 0.010 0.005 0.000 -0.005 -0.010 -0.015 4.0 4.5 5.0 5.5 Vin - Input Voltage - V 6.0 The AC characteristics are also quite impressive offering a -3 dB bandwidth of 100 KHz, with a -45° phase shift at 80 KHz as shown in Figure 21. Figure 21. Amplitude and phase power supply control 2 45 0 0 dB PHASE -2 -45 -4 -90 -6 -135 -8 10 3 10 4 10 5 F - Frequency - Hz Phase Response - ° Max. Linearity Error - % Min. Amplitude Rresponse - dB Bins -180 10 6 The same procedure can be used to design isolation amplifiers that accept biploar signals referenced to ground. These amplifiers circuit configurations are shown in Figure 22. In order for the amplifier to respond to a signal that swings above and below ground, the LED must be prebiased from a separate source by using a voltage reference source (Vref1). In these designs, R3 can be determined by the following equation. V ref1 V ref1 R3 = -----------I - = -------------K1I P1 Figure 19. Transfer gain Fq 3.75 Vout - Ooutput Voltage - V Vout = 14.4 mV + 0.6036 x Vin 3.50 LM 201 Ta = 25°C 3.25 3.00 2.75 2.50 2.25 4.0 4.5 5.0 5.5 Vin - Input Voltage - V 6.0 IL300 5–7 Figure 22. Non-inverting and inverting amplifiers Non-Inverting Input Vin R1 Non-Inverting Output –Vcc 3 + 7 Vcc 1 6 100Ω 2 R2 2– –Vcc +Vcc 3 4 20pF 4 R3 +Vref2 R5 IL 300 8 7 6 2– Vcc 3+ 5 R6 7 Vcc 6 Vo –Vcc 4 R4 –Vref1 Inverting Output Inverting Input Vin R1 3 + 7 Vcc 6 100Ω 1 R2 Vcc +Vcc 2 2 – 4 20pF 3 R3 –Vcc +Vref2 IL 300 8 7 6 3+ Vcc 5 4 2– 7 Vcc –Vcc 4 6 Vout +Vref1 R4 Table 2. Optolinear amplifiers Amp[ifier Input Output Inverting Inverting Non-Inverting Non-Inverting Inverting Non-Inverting Non-Inverting Inverting Non-Inverting Inverting Gain Offset VOUT K3 R4 R2 = VIN R3 (R1+R2) VOUT K3 R4 R2 (R5+R6) = VIN R3 R5 (R1 +R2) Vref2= Vref2= Vref1 R4 K3 R3 –Vref1 R4 (R5+R6) K3 R3 R6 VOUT –K3 R4 R2 (R5+R6) = VIN R3 R5 (R1 +R2) Vref2= Vref1 R4 (R5+R6) K3 R3 R6 VOUT –K3 R4 R2 = VIN R3 (R1 +R2) Vref2= –Vref1 R4 K3 R3 These amplifiers provide either an inverting or non-inverting transfer gain based upon the type of input and output amplifier. Table 2 shows the various configurations along with the specific transfer gain equations. The offset column refers to the calculation of the output offset or Vref2 necessary to provide a zero voltage output for a zero voltage input. The non-inverting input amplifier requires the use of a bipolar supply, while the inverting input stage can be implemented with single supply operational amplifiers that permit operation close to ground. For best results, place a buffer transistor between the LED and output of the operational amplifier when a CMOS opamp is used or the LED IFq drive is targeted to operate beyond 15 mA. Finally the bandwidth is influenced by the magnitude of the closed loop gain of the input and output amplifiers. Best bandwidths result when the amplifier gain is designed for unity. IL300 5–8