VSMS3700 Vishay Semiconductors Infrared Emitting Diode, 950 nm, GaAs FEATURES * Package type: surface mount * Package form: PLCC-2 * Dimensions (L x W x H in mm): 3.5 x 2.8 x 1.75 * Peak wavelength: p = 950 nm * High reliability * Angle of half intensity: = 60 * Low forward voltage * Suitable for high pulse current operation 94 8553 * Good spectral photodetectors matching with Si * Package matched with IR emitter series VEMT3700 * Floor life: 168 h, MSL 3, acc. J-STD-020 DESCRIPTION * Lead (Pb)-free reflow soldering VSMS3700 is an infrared, 950 nm emitting diode in GaAs technology, molded in a PLCC-2 package for surface mounting (SMD). * AEC-Q101 qualified * Compliant to RoHS directive 2002/95/EC and in accordance to WEEE 2002/96/EC * Find out more about Vishay's Automotive Grade Product requirements at: www.vishay.com/applications APPLICATIONS * Infrared source in tactile keyboards * IR diode in low space applications * PCB mounted infrared sensors * Emitter in miniature photo-interrupters PRODUCT SUMMARY COMPONENT Ie (mW/sr) (deg) P (nm) tr (ns) 4.5 60 950 800 VSMS3700 Note Test conditions see table "Basic Characteristics" ORDERING INFORMATION ORDERING CODE PACKAGING REMARKS PACKAGE FORM VSMS3700-GS08 Tape and reel MOQ: 7500 pcs, 1500 pcs/reel PLCC-2 VSMS3700-GS18 Tape and reel MOQ: 8000 pcs, 8000 pcs/reel PLCC-2 Note MOQ: minimum order quantity ** Please see document "Vishay Material Category Policy": www.vishay.com/doc?99902 Document Number: 81373 Rev. 1.3, 03-Nov-09 For technical questions, contact: emittertechsupport@vishay.com www.vishay.com 322 VSMS3700 Infrared Emitting Diode, 950 nm, GaAs Vishay Semiconductors ABSOLUTE MAXIMUM RATINGS PARAMETER TEST CONDITION SYMBOL VALUE UNIT Reverse voltage VR 5 V Forward current IF 100 mA mA Peak forward current tp/T = 0.5, tp = 100 s IFM 200 Surge forward current tp = 100 s IFSM 1.5 A PV 170 mW C Power dissipation Junction temperature Tj 100 Operating temperature range Tamb - 40 to + 85 C Storage temperature range Tstg - 40 to + 100 C Acc. figure 11, J-STD-020 Tsd 260 C J-STD-051, soldered on PCB RthJA 250 K/W Soldering temperature Thermal resistance junction/ambient Note Tamb = 25 C, unless otherwise specified 120 160 IF - Forward Current (mA) PV - Power Dissipation (mW) 180 140 120 100 RthJA = 250 K/W 80 60 40 100 80 60 RthJA = 250 K/W 40 20 20 0 0 0 10 21341 20 30 40 50 60 70 80 90 0 100 Tamb - Ambient Temperature (C) 21342 Fig. 1 - Power Dissipation Limit vs. Ambient Temperature 10 20 30 40 50 60 70 80 90 100 Tamb - Ambient Temperature (C) Fig. 2 - Forward Current Limit vs. Ambient Temperature BASIC CHARACTERISTICS PARAMETER Forward voltage Temperature coefficient of VF Reverse current Junction capacitance TEST CONDITION SYMBOL TYP. MAX. IF = 100 mA, tp = 20 ms VF MIN. 1.3 1.7 IF = 1 A, tp = 100 s VF 1.8 IF = 100 mA TKVF - 1.3 VR = 5 V IR VR = 0 V, f = 1 MHz, E = 0 Cj mV/K 30 A pF IF = 100 mA, tp = 20 ms Ie IF = 1.5 A, tp = 100 s Ie 35 IF = 100 mA, tp = 20 ms e 15 mW IF = 100 mA TKe - 0.8 %/K 60 deg Peak wavelength IF = 100 mA p 950 nm Spectral bandwidth IF = 100 mA 50 nm Temperature coefficient of p IF = 100 mA TKp 0.2 nm/K IF = 20 mA tr 800 ns IF = 1 A tr 400 ns IF = 20 mA tf 800 ns IF = 1 A tf 400 ns EN 60825-1 d 0.5 mm Radiant intensity Radiant power Temperature coefficient of e Angle of half intensity Rise time Fall time Virtual source diameter 4.5 V V 100 1.6 UNIT 8 mW/sr mW/sr Note Tamb = 25 C, unless otherwise specified www.vishay.com 323 For technical questions, contact: emittertechsupport@vishay.com Document Number: 81373 Rev. 1.3, 03-Nov-09 VSMS3700 Infrared Emitting Diode, 950 nm, GaAs Vishay Semiconductors BASIC CHARACTERISTICS Tamb = 25 C, unless otherwise specified 100 10 000 IF - Forward Current (mA) Ie - Radiant Intensity (mW/sr) Tamb < 60 C tp/T = 0.005 0.01 1000 0.02 0.05 100 0.2 0.5 DC 0.1 10 1 0.01 0.1 1 tp - Pulse Length (ms) 95 9985 100 e - Radiant Power (mW) I F - Forward Current (mA) 103 104 IF - Forward Current (mA) 1000 10 3 10 2 10 1 10 0 0 1 2 3 100 10 1 0.1 100 4 V F - Forward Voltage (V) 94 7996 101 102 103 104 IF - Forward Current (mA) 94 8012 Fig. 7 - Radiant Power vs. Forward Current Fig. 4 - Forward Current vs. Forward Voltage 1.2 1.6 1.1 1.2 IF = 10 mA Ie rel; e rel VF rel - Relative Forward Voltage (V) 102 Fig. 6 - Radiant Intensity vs. Forward Current 10 4 1.0 0.9 IF = 20 mA 0.8 0.4 0.8 0.7 0 94 7990 101 94 7956 Fig. 3 - Pulse Forward Current vs. Pulse Duration 10 -1 1 0.1 100 10 10 20 40 60 80 100 Tamb - Ambient Temperature (C) Fig. 5 - Relative Forward Voltage vs. Ambient Temperature Document Number: 81373 Rev. 1.3, 03-Nov-09 0 - 10 0 10 94 7993 50 140 100 T amb - Ambient Temperature (C) Fig. 8 - Relative Radiant Intensity/Power vs. Ambient Temperature For technical questions, contact: emittertechsupport@vishay.com www.vishay.com 324 VSMS3700 Vishay Semiconductors Infrared Emitting Diode, 950 nm, GaAs 0 10 20 1.0 0.75 0.5 0.25 IF = 100 mA 0 900 0.9 50 0.8 60 70 0.7 1000 950 80 0.6 0.4 0.2 0 94 8013 - Wavelength (nm) 94 7994 40 1.0 - Angular Displacement 30 Ie, rel - Relative Radiant Intensity e rel - Relative Radiant Power 1.25 Fig. 9 - Relative Radiant Power vs. Wavelength Fig. 10 - Relative Radiant Intensity vs. Angular Displacement PACKAGE DIMENSIONS in millimeters technical drawings according to DIN specifications 0.9 1.75 0.1 3.5 0.2 Pin identification Mounting Pad Layout 4 A area covered with solder resist 2.6 (2.8) C 2.2 2.8 0.15 1.2 4 O 2.4 1.6 (1.9) 3 + 0.15 Drawing-No.: 6.541-5067.01-4 Issue: 5; 04.11.08 20541 Die Position (for reference only) X = +/- 0.2 mm centrical Y = +/- 0.2 mm centrical Z = 1.13 mm +/- 0.25 mm, from top of die bottom of component www.vishay.com 325 For technical questions, contact: emittertechsupport@vishay.com Document Number: 81373 Rev. 1.3, 03-Nov-09 VSMS3700 Infrared Emitting Diode, 950 nm, GaAs Vishay Semiconductors SOLDER PROFILE 300 255 C 240 C 217 C Temperature (C) 250 2.2 2.0 3.5 3.1 max. 260 C 245 C 5.75 5.25 200 max. 30 s 150 3.6 3.4 max. 100 s max. 120 s 4.0 3.6 8.3 7.7 100 1.85 1.65 max. ramp up 3 C/s max. ramp down 6 C/s 50 1.6 1.4 4.1 3.9 0 0 50 100 150 200 250 4.1 3.9 0.25 2.05 1.95 300 94 8668 19841 Time (s) Fig. 11 - Lead (Pb)-free Reflow Solder Profile acc. J-STD-020 Fig. 13 - Tape Dimensions in mm for PLCC-2 DRYPACK MISSING DEVICES Devices are packed in moisture barrier bags (MBB) to prevent the products from moisture absorption during transportation and storage. Each bag contains a desiccant. A maximum of 0.5 % of the total number of components per reel may be missing, exclusively missing components at the beginning and at the end of the reel. A maximum of three consecutive components may be missing, provided this gap is followed by six consecutive components. FLOOR LIFE Floor life (time between soldering and removing from MBB) must not exceed the time indicated on MBB label: Floor life: 168 h Conditions: Tamb < 30 C, RH < 60 % Moisture sensitivity level 3, acc. to J-STD-020. De-reeling direction 94 8158 DRYING In case of moisture absorption devices should be baked before soldering. Conditions see J-STD-020 or label. Devices taped on reel dry using recommended conditions 192 h at 40 C (+ 5 C), RH < 5 %. TAPE AND REEL > 160 mm Tape leader 40 empty compartments min. 75 empty compartments Carrier leader Carrier trailer Fig. 14 - Beginning and End of Reel PLCC-2 components are packed in antistatic blister tape (DIN IEC (CO) 564) for automatic component insertion. Cavities of blister tape are covered with adhesive tape. The tape leader is at least 160 mm and is followed by a carrier tape leader with at least 40 empty compartments. The tape leader may include the carrier tape as long as the cover tape is not connected to the carrier tape. The least component is followed by a carrier tape trailer with a least 75 empty compartments and sealed with cover tape. Adhesive tape Blister tape Component cavity 94 8670 Fig. 12 - Blister Tape Document Number: 81373 Rev. 1.3, 03-Nov-09 For technical questions, contact: emittertechsupport@vishay.com www.vishay.com 326 VSMS3700 Vishay Semiconductors Infrared Emitting Diode, 950 nm, GaAs COVER TAPE REMOVAL FORCE 10.0 9.0 120 4.5 3.5 2.5 1.5 The removal force lies between 0.1 N and 1.0 N at a removal speed of 5 mm/s. In order to prevent components from popping out of the blisters, the cover tape must be pulled off at an angle of 180 with regard to the feed direction. 13.00 12.75 63.5 60.5 Identification Label: Vishay type group tape code production code quantity 14.4 max. 180 178 94 8665 Fig. 15 - Dimensions of Reel-GS08 10.4 8.4 120 4.5 3.5 2.5 1.5 13.00 12.75 62.5 60.0 Identification Label: Vishay type group tape code production code quantity 321 329 14.4 max. 18857 Fig. 16 - Dimensions of Reel-GS18 www.vishay.com 327 For technical questions, contact: emittertechsupport@vishay.com Document Number: 81373 Rev. 1.3, 03-Nov-09 Measurement Techniques www.vishay.com Vishay Semiconductors Measurement Techniques INTRODUCTION VS = 80 V ( > VR max.) The characteristics of optoelectronics devices given in datasheets are verified either by 100 % production tests followed by statistic evaluation or by sample tests on typical specimens. These tests can be divided into following categories: I = 10 A 100 A constant * Dark measurements VR * Light measurements * Measurements of switching frequency and capacitance characteristics, V cut-off Ri > 10 M * Angular distribution measurements 94 8206 * Spectral distribution measurements Fig. 2 * Thermal measurements Dark and light measurements limits are 100 % measurements. All other values are typical. The basic circuits used for these measurements are shown in the following sections. The circuits may be modified slightly to accommodate special measurement requirements. For most devices, VR is specified at 10 A reverse current. In this case either a high impedance voltmeter has to be used, or current consumption of DVM has to be calculated and added to the specified current. A second measurement step will then give correct readings. Most of the test circuits may be simplified by use of a source measure unit (SMU), which allows either to source voltage and measure current or to source current and measure voltage. In case of IR diodes, total radiant output power, e, is usually measured. This is done with a calibrated large-area photovoltaic cell fitted in a conical reflector with a bore which accepts the test item - see figure 3. An alternative test set uses a silicon photodiode attached to an integrating sphere. A constant DC or pulsating forward current of specified magnitude is passed through the IR diode. The advantage of pulse-current measurements at room temperature (25 C) is that results can be reproduced exactly. DARK AND LIGHT MEASUREMENTS EMITTER DEVICES IR Diodes Forward voltage, VF, is measured either on a curve tracer or statically using the circuit shown in figure 1. A specified forward current (from a constant current source) is passed through the device and the voltage developed across it is measured on a high-impedance voltmeter. Photo Voltaic Cell, Calibrated VS = 5 V I = 50 mA 100 mA constant IF VF V 94 8155 R i > 10 k Reflector 948205 Fig. 3 Fig. 1 To measure reverse voltage, VR, a 10 A or 100 A reverse current from a constant current source is impressed through the diode (figure 2) and the voltage developed across is measured on a voltmeter of high input impedance ( 10 M). Rev. 1.4, 31-Jul-12 If, for reasons of measurement economy, only DC measurements (figure 4) are to be made, then the energizing time should be kept short (below 1 s) and of uniform duration, to minimize any fall-off in light output due to internal heating. Document Number: 80085 1 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors DETECTOR DEVICES Photovoltaic cells, photodiodes VS = 5 V * Dark measurements I = 100 mA constant The reverse voltage characteristic, VR, is measured either on a curve tracer or statically using the circuit shown in figure 6. A high-impedance voltmeter, which draws only an insignificant fraction of device's reverse current, must be used. Ik RL V VS > VR Ri 10 k RL = 1 to 10 IR = 100 A constant 94 8207 Fig. 4 E=0 To ensure that the relationship between irradiance and photocurrent is linear, the photodiode should operate near the short-circuit configuration. This can be achieved by using a low resistance load ( 10 ) of such a value that the voltage dropped across is very much lower than the open circuit voltage produced under identical illumination conditions (Rmeas << Ri). The voltage across the load should be measured with a sensitive DVM. A knowledge of radiant intensity, Ie, produced by an IR emitter enables customers to assess the range of IR light barriers. The measurement procedure for this is more or less the same as the one used for measuring radiant power. The only difference is that in this case the photodiode is used without a reflector and is mounted at a specified distance from, and on the optical axis of, the IR diode (figure 5). This way, only the radiant power of a narrow axial beam is considered. The radiant power within a solid angle of = 0.01 steradian (sr) is measured at a distance of 100 mm. Radiant intensity is then obtained by using this measured value for calculating the radiant intensity for a solid angle of = 1 sr. VF V Ri 10 M 94 8209 Fig. 6 Dark reverse current measurements, Iro, must be carried out in complete darkness - reverse currents of silicon photodiodes are in the range of nanoamperes only, and an illumination of a few lx is quite sufficient to falsify the test result. If a highly sensitive DVM is to be used, then a current sampling resistor of such a value that voltage dropped across it is small in comparison with supply voltage must be connected in series with the test item (figure 7). Under these conditions, any reverse voltage variations of the test samples can be ignored. Shunt resistance (dark resistance) is determined by applying a very slight voltage to the photodiode and then measuring dark current. In case of 10 mV or less, forward and reverse polarity will result in similar readings. VS = 20 V Photo Voltaic Cell with Filter (Calibrated), 1 cm 2 E=0 = 0.01 sr Iro 10 k mV Ri 1 M a = 100 mm 94 8210 Position of the Emitting Area Fig. 5 Fig. 7 94 8156 * Light measurements The same circuit as used in dark measurement can be used to carry out light reverse current, Ira, measurements on photodiodes. The only difference is the diode is now irradiated and a current sampling resistor of lower value must be used (figure 8), because of the higher currents involved. Rev. 1.4, 31-Jul-12 Document Number: 80085 2 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors the same lux and color temperature calibration) may result in readings that differ up to 20 %. VS = 20 V EA = 1 klx or Ee = 1 mW/cm2 The simplest way to overcome this problem is to calibrate (measure the light current) some items of a photodetector type with a standard lamp (OSRAM WI 41/G) and then use these devices for adjustment of the lamp used for field measurements. Ira 10 An IR diode is used as a radiation source (instead of a Tungsten incandescent lamp), to measure detector devices being used mainly in IR transmission systems together with IR emitters (e.g., IR remote control, IR headphone). Operation is possible both with DC or pulsed current. mV Ri = 10 k The adjustment of irradiance, Ee, is similar to the above mentioned adjustment of illuminance, Ev. To achieve a high stability similar to filament lamps, consideration should be given to the following two points: 94 8211 Fig. 8 The open circuit voltage, VO, and short circuit current, Ik, of photovoltaic cells and photodiodes are measured by means of the test circuit shown in figure 9. The value of the load resistor used for the Ik measurement should be chosen so that the voltage dropped across it is low in comparison with the open circuit voltage produced under conditions of identical irradiation. * The IR emitter should be connected to a good heat sink to provide sufficient temperature stability. * DC or pulse-current levels as well as pulse duration have great influence on self-heating of IR diodes and should be chosen carefully. * The radiant intensity, Ie, of the device is permanently controlled by a calibrated detector. Phototransistors The collector emitter voltage, VCEO, is measured either on a transistor curve tracer or statically using the circuit shown in figure 10. Normal bench illumination does not change the measured result. 1 to 10 EA = 1 klx or Ee = 1 mW/cm2 VO Ik mV Ri 10 M VS = 80 V ( < VCEO ) 94 8212 Fig. 9 The light source used for the light measurements is a calibrated incandescent tungsten lamp with no filters. The filament current is adjusted for a color temperature of 2856 K (standard illuminant A to DIN 5033 sheet 7). A specified illumination, Ev, (usually 100 lx or 1000 lx) is produced by adjusting the distance, a, between the lamp and a detector on an optical bench. Ev can be measured on a V()-corrected luxmeter, or, if luminous intensity, Iv, of the lamp is known, Ev can be calculated using the formula: Ev = Iv/a2. It should be noted that this inverse square law is only strictly accurate for point light sources, that is for sources where the dimensions of the source (the filament) are small ( 10 %) in comparison with the distance between the source and detector. Since lux is a measure for visible light only, near-infrared radiation (800 nm to 1100 nm) where silicon detectors have their peak sensitivity is not taken into account. Unfortunately, the near-infrared emission of filament lamps of various construction varies widely. As a result, light current measurements carried out with different lamps (but Rev. 1.4, 31-Jul-12 IC = 1 mA constant E < 100 lx VCEO V Ri 1 M 94 8213 Fig. 10 In contrast, however, the collector dark current, ICEO or ICO, must be measured in complete darkness (figure 11). Even ordinary daylight illumination of the wire fed-through glass seals would falsify the measurement result. Document Number: 80085 3 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors VS = 5 V VS = 20 V ICO IC = constant E=0 Ee = 1 mW/cm2 or EA = 1 klx VCEsat mV 10 k V Ri = 1 M Ri 1 M 94 8214 94 8216 Fig. 11 Fig. 13 The same circuit is used for collector light current, Ica, measurements (figure 12). The optical axis of the device is aligned to an incandescent tungsten lamp with no filters, producing a CIE illuminance A of 100 lx or 1000 lx with a color temperature of Tf = 2856 K. Alternatively an IR irradiance by a GaAs diode can be used (refer to the photovoltaic cells and photodiodes section). Note that a lower sampling resistor is used, in keeping with the higher current involved. SWITCHING CHARACTERISTICS Definition Each electronic device generates a certain delay between input and output signals as well as a certain amount of amplitude distortion. A simplified circuit (figure 14) shows how input and output signals of optoelectronic devices can be displayed on a dual-trace oscilloscope. VS = 5 V VS VS Channel II Channel II IF Channel II Ica Ee = 1 mW/cm2 or EA = 1 klx GaAs-Diode Channel I 94 8219 1 to 10 mV Ri 10 k 94 8215 Fig. 12 Fig. 14 The switching characteristics can be determined by comparing the timing of output current waveform with the input current waveform (figure 15). To measure collector emitter saturation voltage, VCEsat, the device is illuminated and a constant collector current is passed through. The magnitude of this current is adjusted below the level of the minimum light current, Ica min, for the same illuminance (figure 13). The saturation voltage of the phototransistor (approximately 100 mV) is then measured on a high impedance voltmeter. Rev. 1.4, 31-Jul-12 Document Number: 80085 4 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors TECHNICAL DESCTIPTION - ASSEMBLY IF Emitter 0 tp IC t 100 % 90 % 10 % 0 tr td ts t on tp td tr t on (= td + tr) Pulse duration Delay time Rise time Turn-on time tf t off ts tf t off (= ts + tf) t Storage time Fall time Turn-off time 96 11698 Emitters are manufactured using the most modern liquid phase epitaxy (LPE) process. By using this technology, the number of undesirable flaws in the crystal is reduced. This results in a higher quantum efficiency and thus higher radiation power. Distortions in the crystal are prevented by using mesa technology which leads to lower degradation. A further advantage of the mesa technology is that each individual chip can be tested optically and electrically, even on the wafer. DETECTOR Vishay Semiconductor detectors have been developed to match perfectly to emitters. They have low capacitance, high photosensitivity, and extremely low saturation voltage. Silicon nitride passivation protects surface against possible impurities. Fig. 15 Assembly These time parameters also include the delay existing in a luminescence diode between forward current (IF) and radiant power e). Notes Concerning the Test Set-up Circuits used for testing IR emitting, emitting sensitive and optically coupled isolator devices are basically the same (figure 14). The only difference is the way in which test device is connected to the circuit. It is assumed that rise and fall times associated with the signal source (pulse generator) and dual trace oscilloscope are insignificant, and that the switching characteristics of any radiant sensitive device used in set-up are considerably shorter than those of the test item. The switching characteristics of IR emitters, for example (tr 10 ns to 1000 ns), are measured with aid of a PIN Photodiode detector (tr 1 ns). Photo- and darlington transistors and photo- and solar cells (tr 0.5 s to 50 s) are, as a rule, measured by use of fast IR diodes (tr < 30 ns) as emitters. Red light-emitting diodes are used as light sources only for devices which cannot be measured with IR diodes because of their spectral sensitivity (e.g. BPW21R). These diodes emit only 1/10 of radiant power of IR diodes and consequently generate only very low signal levels. Components are fitted onto lead frames by fully automatic equipment using conductive epoxy adhesive. Contacts are established automatically with digital pattern recognition using well-proven thermosonic techniques. All component are measured according to the parameter limits given in the datasheet. Applications Silicon photodetectors are used in manifold applications, such as sensors for radiation from near UV over visible to near infrared. There are numerous applications in measurement of light, such as dosimetry in UV, photometry, and radiometry. A well known application is shutter control in cameras. Another large application area for detector diodes, and especially phototransistors, is position sensing. Examples are differential diodes, optical sensors, and reflex sensors. Other types of silicon detectors are built-in as parts of optocouplers. One of the largest application areas is remote control of TV sets and other home entertainment appliances. Different applications require specialized detectors and also special circuits to enable optimized functioning. Switching Characteristic Improvements on Phototransistors and Darlington Phototransistors As in any ordinary transistor, switching times are reduced if drive signal level, and hence collector current, is increased. Another time reduction (especially in fall time tf) can be achieved by use of a suitable base resistor, assuming there is an external base connection, although this can only be done at the expense of sensitivity. Rev. 1.4, 31-Jul-12 Document Number: 80085 5 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors Equivalent circuit Photodetector diodes can be described by the electrical equivalent circuit shown in figure 16. I sh Photodiodes are often operated in photovoltaic mode, especially in light meters. This is depicted in figure 17, where a strong logarithmic dependence of the open circuit voltage on the input signal is used. I0 Rs R1 Id I ph VD V0 V0 R sh RL R2 94 8606 94 8607 Fig. 16 Fig. 17 - Photodiode in the Photovoltaic Mode Operating with a Voltage Amplifier I O = I ph - ID - I sh qV D - - 1 - I sh I O = I ph - Is exp --------- kT S ( ) x e - I sh V OC = V T x ln -------------------------------------- + 1 Is (1) (2) As described in the chapter "I-V Characteristics of illuminated pn junction", the incident radiation generates a photocurrent loaded by a diode characteristic and load resistor, RL. Other parts of the equivalent circuit (parallel capacitance, C, combined from junction, Cj, and stray capacitances, serial resistance, RS, and shunt resistance, Rsh, representing an additional leakage) can be neglected in most standard applications, and are not expressed in equations 5 and 7 (see "Physics and Technology"). However, in applications with high frequencies or extreme irradiation levels, these parts must be regarded as limiting elements. Searching for the right detector diode type The BPW 20 RF photodiode is based on rather highly doped n-silicon, while BPW34 is a PIN photodiode based on very lightly doped n-silicon. Both diodes have the same active area and spectral response as a function of wavelength is very similar. These diodes differ in their junction capacitance and shunt resistance. Both can influence the performance of an application. Detecting very small signals is the domain of photodiodes with their very small dark currents and dark/shunt resistances. With a specialized detector technology, these parameters are very well controlled in all Vishay photodetectors. R1 V O V OC x 1 + ------ with R2 (3) S ( ) x e - I sh V OC = V T x ln -------------------------------------- + 1 Is (2) It should be noted that extremely high shunt/dark resistance (more than 15 G) combined with a high-impedance operational amplifier input and a junction capacitance of about 1 nF can result in slow switch-off time constants of some seconds. Some instruments therefore have a reset button for shortening the diode before starting a measurement. The photovoltaic mode of operation for precise measurements should be limited to the range of low ambient temperatures, or a temperature control of the diode (e.g., using a Peltier cooler) should be applied. At high temperatures, dark current is increased (see figure 18) leading to a non-logarithmic and temperature dependent output characteristic (see figure 19). The curves shown in figure 18 represent typical behavior of these diodes. Guaranteed leakage (dark reverse current) is specified with Iro = 30 nA for standard types. This value is far from that one which is typically measured. Tighter customer specifications are available on request. The curve shown in figure 19 show the open circuit voltage as a function of irradiance with dark reverse current, IS, as a parameter (in a first approximation increasing IS and Ish have the same effect). The parameter shown covers the possible spread of dark current. In combination with figure 18 one can project the extreme dependence of the open circuit voltage at high temperatures (figure 20). The very small leakage currents of photodiodes are offset by higher capacitances and smaller bandwidths in comparison to PIN photodiodes. Rev. 1.4, 31-Jul-12 Document Number: 80085 6 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors Operating modes and circuits The advantages and disadvantages of operating a photodiode in open circuit mode have been discussed. 107 Reverse Bias Voltage Vr = 20 V Current (nA) 105 BPW24R 103 BPW20RF 101 10-1 - 20 0 20 60 100 140 Temperature (C) 94 8608 Open Circuit Voltage (mV) Fig. 18 - Reverse Dark Current vs. Temperature Between these wavelength boundaries the output is almost independent of temperature. By using this mode of operation, the reverse biased or unbiased (short circuit conditions), output voltage, VO, will be directly proportional to incident radiation, e (see equation in figure 21). 400 10 pA R 300 100 pA V0 200 1 nA 5 nA 100 0 0.01 94 8611 Fig. 21 - Transimpedance Amplifier, Current to Voltage Converter, Short Circuit Mode 30 nA 0.1 1 10 100 1000 Irradiance (W) 94 8609 Fig. 19 - Open Circuit Voltage vs. Irradiance, Parameter: Dark Reverse Current, BPW20RF Open Circuit Voltage (mV) For operation in short circuit mode (see figure 21) or photoconductive mode (see figure 22), current-to-voltage converters are typically used. In comparison with photovoltaic mode, the temperature dependence of the output signal is much lower. Generally, the temperature coefficient of the light reverse current is positive for irradiation with wavelengths > 900 nm, rising with increasing wavelength. For wavelengths < 600 nm, a negative temperature coefficient is found, likewise with increasing absolute value to shorter wavelengths. VO = - R x e x S ( ) (4) V OC = - I sc x R (5) Vb 400 R 300 200 V0 100 94 8612 0 0 94 8610 20 40 60 80 100 Temperature (C) Fig. 20 - Open Circuit Voltage vs. Temperature, BPW46 Rev. 1.4, 31-Jul-12 Fig. 22 - Transimpedance Amplifier, Current to Voltage Converter, Reverse Biased Photodiode The circuit in figure 21 minimizes the effect of reverse dark current while the circuit in figure 22 improves the speed of the detector diode due to a wider space charge region with decreased junction capacitance and field increased velocity of the charge carrier transport. Document Number: 80085 7 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors 30 Rise Time tr, Fall Time tf (s) Vb V0 R1 C R3 R2 25 tr = 0 V tf = 0 V tr = - 0 V tf = - 10 V 20 15 10 5 0 550 600 650 700 750 800 850 900 950 94 8613 Wavelength (nm) 948615 Fig. 23 - RC-Loaded Photodiode with Voltage Amplifier Fig. 25 - Switching Times vs. Wavelength for Photodiode BPW20RF Figure 23 shows photocurrent flowing into an RC load, where C represents junction and stray capacity while R3 can be a real or complex load, such as a resonant circuit for the operating frequency. A drastic increase in rise and fall times is observed at wavelengths > 850 nm. Differences between unbiased and biased operation result from the widening of the space charge region. However, for PIN photodiodes (BPW34/TEMD5000 family) similar results with shifted time scales are found. An example of such behavior, in this case in the frequency domain, is presented in figure 26 for a wavelength of 820 nm and figure 27 for 950 nm. Vb C2 12 V0 RL = 100 k Reverse Bias (V) 10 R1 C1 R3 R2 94 8614 Fig. 24 - AC-Coupled Amplifier Circuit 10 k 8 1 k 6 4 50 2 0 (6) The circuit in figure 24 is equivalent to figure 23 with a change to AC coupling. In this case, the influence of background illumination can be separated from a modulated signal. The relation between input signal (irradiation, e) and output voltage is given by the equation in figure 24. Frequency response The limitations of switching times in photodiodes are determined by carrier lifetime. Due to the absorption properties of silicon, especially in photodiodes, most of incident radiation at longer wavelengths is absorbed outside the space charge region. Therefore, a strong wavelength dependence of the switching times can be observed (figure 25). 104 94 8616 105 106 107 108 - 3 dB - Bandwidth (Hz) Fig. 26 - BPW34, TEMD5010X01, Bandwidth vs. Reverse Bias Voltage, Parameter: Load Resistance, = 820 nm 12 10 Reverse Bias (V) R1 V O e x S ( ) x R 3 x 1 + -----R2 8 RL = 1 M 1 k 100 k 10 k 6 50 4 2 0 103 94 8617 104 105 106 107 - 3 dB - Bandwidth (Hz) Fig. 27 - BPW41, TEMD5110X01, Bandwidth vs. Reverse Bias Voltage, Parameter: Load Resistance = 950 nm Rev. 1.4, 31-Jul-12 Document Number: 80085 8 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Measurement Techniques www.vishay.com Vishay Semiconductors Below about 870 nm, only slight wavelength dependence can be recognized, while a steep change of cut-off frequency takes place from 870 nm to 950 nm (different time scales in figure 26 and figure 27). Additionally, the influence of load resistances and reverse bias voltages can be taken from these diagrams. For cut-off frequencies greater than 10 MHz to 20 MHz, depending on the supply voltage available for biasing the detector diode, PIN photodiodes are also used. However, for this frequency range, and especially when operating with low bias voltages, thin epitaxially grown intrinsic (i) layers are incorporated into PIN photodiodes. As a result, these diodes (e.g., Vishay's TESP5700) can operate with low bias voltages (3 V to 4 V) with cut-off frequencies of 300 MHz at a wavelength of 790 nm. With application-specific optimized designs, PIN photodiodes with cut-off frequencies up to 1 GHz at only a 3 V bias voltage with only an insignificant loss of responsivity can be generated. The main applications for these photodiodes are found in optical local area networks operating in the first optical window at wavelengths of 770 nm to 880 nm. WHICH TYPE FOR WHICH APPLICATION? In table 1, selected diode types are assigned to different applications. For more precise selection according to chip sizes and packages, refer to the tables in introductory pages of this data book. TABLE 1 - PHOTODIODE REFERENCE TABLE DETECTOR APPLICATION PIN PHOTODIODE PHOTODIODE TEMD5010X01, BPW34, BPW24R, ... BPW20RF Photometry, light meter Radiometry BPW21R Light barriers Remote control, IR filter included, > 900 nm IR Data Transmission fc < 10 MHz IR filter included, > 820 nm IR Data Transmission, fc > 10 MHz, no IR filter Densitometry Smoke detector BPV10NF, BPW24R BPV20F, BPV23F, BPW41N, S186P, TEMD5100X01 BPV23NF, BPW82, BPW83, BPV10NF, TEMD1020, TEMD5110X01 BPW34, BPW46, BPV10, TEMD5010X01 BPW34, BPV10, TEMD5010X01 BPW20RF, BPW21R BPV22NF, BPW34, TEMD5010X01 PHOTOTRANSISTOR CIRCUITS A phototransistor typically operates in a circuit shown in figure 28. Resistor RB can be omitted in most applications. In some phototransistors, the base terminal is not connected. RB can be used to suppress background radiation by setting a threshold level (see equation 7 and 8) VO = VS - B x e x S ( ) x RL (7) 0.6 V OC V S - B x e x S ( ) - -------- x R L RB (8) For the dependence of rise and fall times on load resistance and collector-base capacitance, see the chapter "Properties of Silicon Phototransistors". Rev. 1.4, 31-Jul-12 Vs 94 8618 RL V0 RB Fig. 28 - Phototransistor with Load Resistor and Optional Base Resistor Document Number: 80085 9 For technical questions, contact: emittertechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Legal Disclaimer Notice www.vishay.com Vishay Disclaimer ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE. 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We confirm that all the products identified as being compliant to IEC 61249-2-21 conform to JEDEC JS709A standards. Revision: 02-Oct-12 1 Document Number: 91000