MONOLITHIC PHOTODIODE AND AMPLIFIER khz Bandwidth at R F = MΩ FEATURES BOOTSTRAP ANODE DRIVE: Extends Bandwidth: 9kHz (R F = KΩ) Reduces Noise LARGE PHOTODIODE:.9" x.9" HIGH RESPONSIVITY:.4A/W (6nm) EXCELLENT SPECTRAL RESPONSE WIDE SUPPLY RANGE: ±. to ±V TRANSPARENT DIP, SIP AND SURFACE- MOUNT PACKAGES APPLICATIONS BARCODE SCANNERS MEDICAL INSTRUMENTATION LABORATORY INSTRUMENTATION POSITION AND PROXIMITY DETECTORS PARTICLE DETECTORS DESCRIPTION The is a photodetector consisting of a high performance silicon photodiode and precision FETinput transimpedance amplifier integrated on a single monolithic chip. Output is an analog voltage proportional to light intensity. The large.9" x.9" photodiode is operated at low bias voltage for low dark current and excellent linearity. A novel photodiode anode bootstrap circuit reduces the effects of photodiode capacitance to extend bandwidth and reduces noise. The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered with discrete designs such as leakage current errors, noise pick-up and gain peaking due to stray capacitance. The operates from ±. to ±V supplies and quiescent current is only ma. Available in a transparent -pin DIP, -lead surface-mount and -pin SIP, it is specified for to 7 C operation. SPECTRAL RESPONSIVITY λ V+ () () + DIP Pins R F () (4) V (SIP Pins) () V O Voltage Output (V/µW)..4... Ultraviolet Blue Using External MΩ Resistor Green Yellow 4 6 7 9 Red Infrared..4... Photodiode Responsivity (A/W) Wavelength (nm) International Airport Industrial Park Mailing Address: PO Box 4 Tucson, AZ 74 Street Address: 67 S. Tucson Blvd. Tucson, AZ 76 Tel: () 746- Twx: 9-9- Cable: BBRCORP Telex: 66-649 FAX: () 9- Immediate Product Info: () 4-6 99 Burr-Brown Corporation PDS-A Printed in U.S.A. December, 99
SPECIFICATIONS At T A = + C, V S = ±V, λ = 6nm, External R F = MΩ, R L = kω, unless otherwise noted. P W PARAMETER CONDITIONS MIN TYP MAX UNITS RESPONSIVITY Photodiode Current λ = 6nm.4 A/W Unit-to-Unit Variation ± % Voltage Output λ = 6nm, External R F = MΩ.4 V/µW Nonlinearity. % of FS Photodiode Area (.9 x.9in). in (.9 x.9mm). mm DARK ERROR, RTO Offset Voltage ± ± mv vs Temperature ± µv/ C vs Power Supply V S = ±.V to ±V µv/v Voltage Noise BW =.Hz to khz 6 µvrms FREQUENCY RESPONSE Bandwidth External R F = MΩ khz Rise Time % to 9%. µs Settling Time, % FS to Dark step µs.% µs.% µs Overload Recovery % Overdrive 7 µs OUTPUT Voltage Output, Positive R L = kω (V+). (V+).7 V Positive R L = kω (V+) Negative () R L = kω.4. V Capacitive Load, Stable Operation pf Short-Circuit Current () + ma POWER SUPPLY Operating Range ±. ± V Quiescent Current +./.7 ±4 ma TEMPERATURE RANGE Specification 7 C Operating 7 C Storage C θ JA C/W NOTES: () Output typically swings to.v below the voltage applied to the non-inverting input terminal, which is normally connected to ground. () Positive current (sourcing) is limited. Negative current (sinking) is not limited. PHOTODIODE SPECIFICATIONS PHOTODIODE PARAMETER CONDITIONS MIN TYP MAX UNITS Photodiode Area (.9 x.9in). in (.9 x.9mm). mm Current Responsivity λ = 6nm.4 A/W 6 µa/w/cm Dark Current V D =.V 7 pa vs Temperature Doubles every C Capacitance V D =.V pf Effective Capacitance () V D =.V pf NOTES: () Effect of photodiode capacitance is reduced by internal buffer bootstrap drive. See text 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.
OP AMP SPECIFICATIONS Op amp specifications provided for comparative information only. OP AMP PARAMETER CONDITIONS MIN TYP MAX UNITS INPUT Offset Voltage ± mv vs Temperature ± µv/ C vs Power Supply µv/v Input Bias Current Inverting Input pa vs Temperature Doubles every C Non-inverting Input µa NOISE Voltage Noise f = Hz nv/ Hz f = Hz 9 nv/ Hz f = khz 6 nv/ Hz Current Noise Density, Inverting Input BW =.Hz to khz. fa/ Hz INPUT VOLTAGE RANGE Common-Mode Input Range () V S ±. V Common-Mode Rejection 6 db INPUT IMPEDANCE Inverting Input Impedance x Ω pf Non-Inverting Input Impedance kω OPEN-LOOP GAIN Open-Loop Voltage Gain V O = V to +.7V 7 db FREQUENCY RESPONSE Bandwidth, Small Signal MHz Rise Time, Large Signal % to 9% ns Settling Time, % V step 4 ns.% 9 ns.% ns Overload Recovery % Overdrive 7 µs OUTPUT Voltage Output, Positive R L = kω (V+). (V+).7 V Positive R L = kω (V+) Negative () R L = kω.4. V Capacitive Load, Stable Operation pf Short-Circuit Current () + ma POWER SUPPLY Operating Voltage ±. ± V Quiescent Current +.7/.4 ±4 ma NOTES: () Output typically swings to.v below the voltage applied to the non-inverting input terminal, which is normally connected to ground. () Positive current (sourcing) is limited. Negative current (sinking) is not limited. BUFFER SPECIFICATIONS Buffer specifications provided for comparative information only. BUFFER PARAMETER CONDITIONS MIN TYP MAX UNITS INPUT Offset Voltage (). V Input Bias Current pa vs Temperature Doubles every C Input Impedance Ω pf FREQUENCY RESPONSE Bandwidth, Small Signal MHz OUTPUT Current ± µa Voltage Gain.99 V/V POWER SUPPLY Operating Range ±. ± V Quiescent Current ±. ma NOTE: () Intentional voltage offset to reverse bias photodiode.
DICE INFORMATION PAD FUNCTION 4 V+ In V Output Common Photodiode Area.9 x.9 inch.9 x.9 mm B Substrate Bias: The substrate is electrically connected to internal circuitry. Do not make electrical connection to the substrate. MECHANICAL INFORMATION A MILS (.") MILLIMETERS Die Size 4 x 4 ±.76 x.64 ±. Die Thickness ±. ±. Min. Pad Size 4 x 4. x. Backing None DIE TOPOGRAPHY 6 7 PIN CONFIGURATIONS Top View Top View V+ In V NC Common V+ In V Output ABSOLUTE MAXIMUM RATINGS Supply Voltage... ±V Input Voltage Range (Common Pin)... ±V S Output Short-Circuit (to ground)... Continuous Operating Temperature: P, W... C to + C Storage Temperature: P, W... C to + C Junction Temperature: P, W... + C Lead Temperature (soldering, s)... + C (Vapor-Phase Soldering Not Recommended on Plastic Packages) PACKAGE INFORMATION 4 Common PACKAGE DRAWING MODEL PACKAGE NUMBER () P -Pin Plastic DIP 6- P-J -Lead Surface Mount () 6-6 W -Pin Plastic SIP - NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. () -pin DIP with leads formed for surface mounting. () 7 6 NC NC NOTE: () Photodiode location. 4 () NOTE: () Photodiode location. Output DIP SIP 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. MOISTURE SENSITIVITY AND SOLDERING Clear plastic does not contain the structural-enhancing fillers used in black plastic molding compound. As a result, clear plastic is more sensitive to environmental stress than black plastic. This can cause difficulties if devices have been stored in high humidity prior to soldering. The rapid heating during soldering can stress wire bonds and cause failures. Prior to soldering, it is recommended that plastic devices be baked-out at C for 4 hours. The fire-retardant fillers used in black plastic are not compatible with clear molding compound. The plastic packages cannot meet flammability test, UL-94. ORDERING INFORMATION MODEL PACKAGE -4-99 + P -Pin DIP $9. $7. $6. P-J -Lead Surface Mount 9. 7. 6. W -Pin Plastic SIP 9. 7. 6. 4
TYPICAL PERFORMANCE CURVES At T A = + C, V S = ±V, λ = 6nm, unless otherwise noted. Normalized Current or Voltage Output...6.4. NORMALIZED SPECTRAL RESPONSIVITY 6nm (.4A/W) Wavelength (nm) (.4A/W) 4 6 7 9 Output Voltage (V)... VOLTAGE RESPONSIVITY vs RADIANT POWER R F = MΩ R F = MΩ R F = kω R F = kω R F = kω.. k Radiant Power (µw) λ = 6nm VOLTAGE RESPONSIVITY vs IRRADIANCE VOLTAGE OUTPUT RESPONSIVITY vs FREQUENCY R F = MΩ Output Voltage (V)... R F = MΩ R F = MΩ R F = kω R F = kω... Irradiance (W/m ) R F = kω λ = 6nm Responsivity (V/µW).. R F = MΩ R F = MΩ, C F =.pf R F = kω, C F =.pf k k k M M Frequency (Hz) Relative Response...6.4. RESPONSE vs INCIDENT ANGLE SIP Package θ X θ X Plastic DIP Package θ Y θ Y θ Y θ X...6.4. Power Supply Rejection (db) 9 7 6 4 POWER SUPPLY REJECTION vs FREQUENCY V+ V ± ±4 ±6 ± Incident Angle ( ) k k k M M Frequency (Hz)
TYPICAL PERFORMANCE CURVES (CONT) At T A = + C, V S = ±V, λ = 6nm, unless otherwise noted. Quiescent Current (ma) QUIESCENT CURRENT vs TEMPERATURE + I Q I Q V S = ±V + I Q I Q V S = ±.V Noise Voltage (Vrms) R 4 F = MΩ 6 OUTPUT NOISE VOLTAGE vs MEASUREMENT BANDWIDTH Dashed lines indicate noise measured beyond the signal bandwidth. R F = MΩ R F = MΩ R F = kω R F = kω 7 SMALL-SIGNAL RESPONSE, R F = MΩ Measurement BW = MHz LARGE-SIGNAL RESPONSE, R F = MΩ mv/div V/div 7 Temperature ( C) 7 k k k M M Frequency (Hz) µs/div µs/div Noise Effective Power (W) 7 9 NOISE EFFECTIVE POWER vs MEASUREMENT BANDWIDTH Dashed lines indicate noise measured beyond the signal bandwidth. λ = 6nm R F = kω R F = kω R F = MΩ R F = MΩ R F = MΩ 4 k k k M M Frequency (Hz) 6
APPLICATIONS INFORMATION Basic operation of the is shown in Figure. Power supply bypass capacitors should be connected near the device pins as shown. Noise performance of the can be degraded by the high frequency noise on the power supplies. Resistors in series with the power supply pins as shown can be used (optional) to help filter power supply noise An external feedback resistor, R F, is connected from In to the V O terminal as shown in Figure. Feedback resistors of MΩ or less require parallel capacitor, C F. See the table of values in Figure. λ µf + +V Ω () () + R F C F (min) BANDWIDTH MΩ () 7kHz MΩ.pF khz kω.pf 9kHz kω pf.6mhz kω pf.6mhz NOTE: () Two series-connected resistors of R F / for low capacitance. See text. FIGURE. Basic Operation. C F R F () Optional series resistors filter power supply noise. See text. Ω (paracitic capacitance) V For R F > MΩ, use series-connected resistors. See text. (4) () µf + V O (V to 4V) Bandwidth varies with feedback resistor value. To achieve widest bandwidth with resistors greater than MΩ, use care to minimize parasitic parallel capacitance. For widest bandwidth with resistors greater than MΩ, connect two resistors (R F /) in series. Airwiring this interconnection provides lowest capacitance. Although the is usable with feedback resistors of MΩ and higher, with R F MΩ the model OPT will provide lower dc errors and reduced noise. The s output voltage is the product of the photodiode current times the external feedback resistor, R F. Photodiode current, I D, is proportional to the radiant power or flux (in watts) falling on the photodiode. At a wavelength of 6nm (visible red) the photodiode Responsivity, R I, is approximately.4a/w. Responsivity at other wavelengths is shown in the typical performance curve Responsivity vs Wavelength. 7 The typical performance curve Output Voltage vs Radiant Power shows the response throughout a wide range of radiant power and feedback resistor values. The response curve Output Voltage vs Irradiance is based on the photodiode area of.x 6 m. BOOTSTRAP BUFFER The photodiode s anode is driven by an internal high speed voltage buffer shown in Figure. This variation on the classical transimpedance amplifier circuit reduces the effects of photodiode capacitance. The effective photodiode capacitance is reduced from approximately pf to pf with this bootstrap drive technique. This improves bandwidth and reduces noise. The output voltage of the buffer is offset approximately.v below the input. This reverse biases the photodiode for reduced capacitance. OP AMP A special op amp design is used to achieve wide bandwidth. The op amp output voltage cannot swing lower than.v below the non-inverting input voltage. Since photodiode current always produces a positive output voltage, this does not limit the required output swing. The inverting input is designed for very low input bias current approximately pa. The non-inverting input has much larger bias current approximately µa flows out of this terminal. µa / REF Ω Ω µa / REF +V.µF λ +V V () () kω + OPA R F MΩ () (4) V A ±mv µa FIGURE. Adjustable Output Offset. V ().µf V O Output voltage offset by V A An offset voltage can be connected to the non-inverting input as shown in Figure. A voltage applied to the noninverting input is summed at the output. Because the noninverting input bias current is high (approximately µa), it should be driven by a low impedance such as the bufferconnected op amp shown.
The can be connected to operate from a single power supply as shown in Figure. The non-inverting input bias current flows through a zener diode to provide a bias voltage. The output voltage is referenced to this bias point. cosine of the incident angle). At a greater incident angle, light is diffused by the side of the package. These effects are shown in the typical performance curve, Response vs Incident Angle. +V.µF () () + µa ZD λ R F () (4) + µf () V O measured relative to.6v zener voltage. V O (.6V) LINEARITY PERFORMANCE Photodiode current is very linear with radiant power throughout its range. Nonlinearity remains below approximately.% up to µa. The anode buffer drive, however, is limited to approximately µa. This produces an abrupt limit to photodiode output current when radiant power reaches approximately 4µW. Best linearity is achieved with the photodiode uniformly illuminated. A light source focused to a very small beam, illuminating only a small percentage of the photodiode area, may produce a higher nonlinearity. ZD : IN466.6V specified at I Z = µa FIGURE. Single Power Supply Operation. DARK ERRORS The dark errors in the specification table include all sources with R F = MΩ. The dominant error source is the input offset voltage of the op amp. Photodiode dark current is approximately 7pA and the combined input bias current of the op amp and buffer is approximately pa. Photodiode dark current and input bias current total approximately pa at C and double for each C above C. At 7 C, the total error current is approximately na. With R F = MΩ, this would produce a mv offset voltage in addition to the initial amplifier offset voltage (mv max) at C. The dark output voltage can be trimmed to zero with the optional circuit shown in Figure. LIGHT SOURCE POSITIONING The is tested with a light source that uniformly illuminates the full integrated circuit area, including the op amp. Although all IC amplifiers are light sensitive to some degree, the op amp circuitry is designed to minimize this effect. Sensitive junctions are shielded with metal where possible. Furthermore, the photodiode area is very large compared to the op amp circuitry making these effects negligible. If your light source is focused to a small area, be sure that it is properly aimed to fall on the photodiode. If a narrowly focused light source were to miss the photodiode and fall on the op amp circuitry, the would not perform properly. The large photodiode area is clearly visible as a very dark area slightly offset from the center of the IC. The incident angle of the light source also affects the apparent sensitivity in uniform irradiance. For small incident angles, the loss in sensitivity is due to the smaller effective light gathering area of the photodiode (proportional to the NOISE PERFORMANCE Noise performance of the is determined by the op amp characteristics in conjunction with the feedback components, photodiode capacitance, and buffer performance. The typical performance curve Output Noise Voltage vs Measurement Bandwidth shows how the noise varies with R F and measured bandwidth (.Hz to the indicated frequency). The signal bandwidth of the is indicated on the curves. Noise can be reduced by filtering the output with a cutoff frequency equal to the signal bandwidth. Output noise increases in proportion to the square-root of the feedback resistance, while responsivity increases linearly with feedback resistance. So best signal-to-noise ratio is achieved with large feedback resistance. This comes with the trade-off of decreased bandwidth. The noise performance of a photodetector is sometimes characterized by Noise Effective Power (NEP). This is the radiant power which would produce an output signal equal to the noise level. NEP has the units of radiant power (watts), or Watts/ Hz to convey spectral information about the noise. The typical performance curve Output Noise Voltage vs Measurement Bandwidth is also scaled for NEP on the right-hand side.