INTEGRATED PHOTODIODE AND AMPLIFIER

FPO 7% ABRIDGED DATA SHEET For Complete Data Sheet Call FaxLine -8-8-633 Request Document Number 8 INTEGRATED PHOTODIODE AND AMPLIFIER FEATURES PHOTODIODE SIZE:.9 x.9 inch (.9 x.9mm) FEEDBACK RESISTOR HIGH RESPONSIVITY:.7A/W (6nm) IMPROVED UV RESPONSE LOW DARK ERRORS: mv BANDWIDTH: khz WIDE SUPPLY RANGE: ±. to ±8V LOW QUIESCENT CURRENT: µa HERMETIC TO-99 APPLICATIONS MEDICAL INSTRUMENTATION LABORATORY INSTRUMENTATION POSITION AND PROXIMITY SENSORS PHOTOGRAPHIC ANALYZERS SMOKE DETECTORS DESCRIPTION The is an opto-electronic integrated circuit containing a photodiode and transimpedance amplifier on a single dielectrically isolated chip. The transimpedance amplifier consists of a precision FETinput op amp and an on-chip metal film resistor. The.9 x.9 inch photodiode is operated at zero bias for excellent linearity and low dark current. The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs such as leakage current errors, noise pick-up and gain peaking due to stray capacitance. The operates over a wide supply range (±. to ±8V) and supply current is only µa. It is packaged in a hermetic TO-99 metal package with a glass window, and is specified for the C to 8 C temperature range. SPECTRAL RESPONSIVITY 7Ω Voltage Output (V/µW)...3.. Ultraviolet Blue Using Internal Resistor Green Yellow Red Infrared...3.. Photodiode Responsivity (A/W) 3 6 7 8 9 Wavelength (nm) International Airport Industrial Park Mailing Address: PO Box, Tucson, AZ 873 Street Address: 673 S. Tucson Blvd., Tucson, AZ 876 Tel: () 76- Twx: 9-9- Internet: http://www.burr-brown.com/ FAXLine: (8) 8-633 (US/Canada Only) Cable: BBRCORP Telex: 66-69 FAX: () 889- Immediate Product Info: (8) 8-63 99 Burr-Brown Corporation PDS-8A Printed in U.S.A. January, 99

SPECIFICATIONS ELECTRICAL At T A = + C, V S = ±V, = 6nm, internal feedback resistor, unless otherwise noted. M PARAMETER CONDITIONS MIN TYP MAX UNITS RESPONSIVITY Photodiode Current 6nm.7 A/W Voltage Output 6nm.7 V/µW vs Temperature ppm/ C Unit-to-Unit Variation 6nm ± % Nonlinearity () FS Output = V. % of FS Photodiode Area (.9 x.9in).8 in (.9 x.9mm). mm DARK ERRORS, RTO () Offset Voltage, Output ±. ± mv vs Temperature ± µv/ C vs Power Supply V S = ±.V to ±8V µv/v Voltage Noise Measured BW =. to khz 6 µvrms RESISTOR Internal Resistance MΩ Tolerance ±. ± % vs Temperature ppm/ C FREQUENCY RESPONSE Bandwidth, Large or Small-Signal, 3dB khz Rise Time, % to 9% 9 µs Settling Time, % FS to Dark µs.% FS to Dark 3 µs.% FS to Dark 9 µs Overload Recovery Time % overdrive, V S = ±V µs % overdrive, V S = ±V µs % overdrive, V S = ±.V µs OUTPUT Voltage Output R L = kω (). ().6 V R L = kω () () V Capacitive Load, Stable Operation nf Short-Circuit Current ±8 ma POWER SUPPLY Specified Operating Voltage ± V Operating Voltage Range ±. ±8 V Quiescent Current I O = ±. ±. ma TEMPERATURE RANGE Specification +8 C Operating/Storage + C Thermal Resistance, θ JA C/W NOTES: () Deviation in percent of full scale from best-fit straight line. () Referred to Output. Includes all error sources. PHOTODIODE SPECIFICATIONS At T A = + C, unless otherwise noted. Photodiode of PARAMETER CONDITIONS MIN TYP MAX UNITS Photodiode Area (.9 x.9in).8 in (.9 x.9mm). mm Current Responsivity 6nm.7 A/W Dark Current V D = V () fa vs Temperature doubles every C Capacitance V D = V () pf NOTE: () Voltage Across Photodiode.

SPECIFICATIONS (CONT) ELECTRICAL Op Amp Section of () At T A = + C, V S = ±V, unless otherwise noted. Op Amp PARAMETER CONDITIONS MIN TYP MAX UNITS INPUT Offset Voltage ±. mv vs Temperature ± µv/ C vs Power Supply V S = ±.V to ±8V µv/v Input Bias Current pa vs Temperature doubles every C NOISE Input Voltage Noise Voltage Noise Density, f=hz 3 nv/ Hz f=hz nv/ Hz f=khz nv/ Hz Current Noise Density, f=khz.8 fa/ Hz INPUT VOLTAGE RANGE Common-Mode Input Range ±. V Common-Mode Rejection 6 db INPUT IMPEDANCE Differential 3 Ω pf Common-Mode 3 Ω pf OPEN-LOOP GAIN Open-Loop Voltage Gain db FREQUENCY RESPONSE Gain-Bandwidth Product 38 khz Slew Rate. V/µs Settling Time.% µs.% µs OUTPUT Voltage Output R L = kω (). ().6 V R L = kω () () V Short-Circuit Current ±8 ma POWER SUPPLY Specified Operating Voltage ± V Operating Voltage Range ±. ±8 V Quiescent Current I O = ±. ±. ma NOTE: () Op amp specifications provided for information and comparison only. 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

DICE INFORMATION Photodiode Area.9 x.9 inch.9 x.9 mm PAD FUNCTION In 3 Feedback Output 6 NC 7 NC 8A, 8B Common NC: No Connection. Pads 8A and 8B must both be connected to common. Substrate Bias: The substrate is electrically connected to internal circuitry. Do not make electrical connection to the substrate. MECHANICAL INFORMATION MILS (.") MILLIMETERS Die Size x ± 3.9 x 3. ±.3 Die Thickness ±3. ±.8 Min. Pad Size x. x. Backing None DIE TOPOGRAPHY PIN CONFIGURATION Top View Common 8 NC 7 Photodiode Area In 6 NC 3 Output Feedback NOTE: Metal package is internally connected to common (Pin 8). 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. PACKAGE INFORMATION PACKAGE DRAWING PRODUCT PACKAGE NUMBER () ABSOLUTE MAXIMUM RATINGS Supply Voltage... ±8V Input Voltage Range (Common Pin)... ±V S Output Short-Circuit (to ground)... Continuous Operating Temperature... C to + C Storage Temperature... C to + C Junction Temperature... + C Lead Temperature (soldering, s)... +3 C M 8-Pin TO-99 - NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ORDERING INFORMATION MODEL PACKAGE - -99 + M 8-Pin TO-99 $8. $3.9 $.

TYPICAL PERFORMANCE CURVES At T A = + C, V S = ±V, = 6nm, unless otherwise noted. Normalized Current or Voltage Output..8.6.. NORMALIZED SPECTRAL RESPONSIVITY 6nm (.7A/W) 3 6 7 8 9 Wavelength (nm) (.A/W) Output Voltage (V)... VOLTAGE RESPONSIVITY vs RADIANT POWER = MΩ = = kω = kω.. k Radiant Power (µw) = 6nm Output Voltage (V)... VOLTAGE RESPONSIVITY vs IRRADIANCE = MΩ = = kω = kω... Irradiance (W/m ) = 6nm Responsivity (V/µW).. VOLTAGE OUTPUT RESPONSIVITY vs FREQUENCY = MΩ = 3.3MΩ = 33kΩ C EXT = 8pF = Frequency (Hz) = 6nm = 33kΩ C EXT = 3pF = kω C EXT = 9pF = kω C EXT = 3pF. k k k M 6 DISTRIBUTION OF RESPONSIVITY. RESPONSE vs INCIDENT ANGLE. Units (%) 3 = 6nm Distribution Totals % Laboratory Test Data Relative Response.8.6. θ.8.6.....6.7.8.9. Responsivity (A/W) ± ± ±6 ±8 Incident Angle ( )

TYPICAL PERFORMANCE CURVES At T A = + C, V S = ±V, = 6nm, unless otherwise noted. Quiescent Current (ma).6...3.. 7 QUIESCENT CURRENT vs TEMPERATURE V S = ±V V S = ±.V Dice 7 Noise Voltage (µvrms). OUTPUT NOISE VOLTAGE vs MEASUREMENT BANDWIDTH Dotted lines show noise beyond the signal bandwidth. = MΩ = MΩ = kω C EXT = 9pF = = kω C EXT = 3pF k k k Temperature ( C) Measurement Bandwidth (Hz) SMALL-SIGNAL DYNAMIC RESPONSE LARGE-SIGNAL DYNAMIC RESPONSE mv/div V/div µs/div µs/div Noise Effective Power (W) 7 8 9 NOISE EFFECTIVE POWER vs MEASUREMENT BANDWIDTH Dotted lines indicate noise measured beyond the signal bandwidth. = 6nm = k = k = M = M = M 3 k k k Measurement Bandwidth (Hz) 6

APPLICATIONS INFORMATION Figure shows the basic connections required to operate the. Applications with high-impedance power supplies may require decoupling capacitors located close to the device pins as shown. Output is zero volts with no light and increases with increasing illumination. I D is proportional to light intensity (radiant power). I D FIGURE. Basic Circuit Connections. (V) NOTE: Metal package is internally connected to common (Pin 8)..µF.µF +V V 7Ω 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.a/w. Responsivity at other wavelengths is shown in the typical performance curve Responsivity vs Wavelength. The typical performance curve Output Voltage vs Radiant Power shows the response throughout a wide range of radiant power. The response curve Output Voltage vs Irradiance is based on the photodiode area of.3 x 6 m. The s voltage output is the product of the photodiode current times the feedback resistor, (I D ). The internal feedback resistor is laser trimmed to ±%. Using this resistor, the output voltage responsivity, R V, is approximately.v/µw at 6nm wavelength. An external resistor can be used to set a different voltage responsivity. For values of less than, an external capacitor, C EXT, should be connected in parallel with (see Figure ). This capacitor eliminates gain peaking and prevents instability. The value of C EXT can be read from the table in Figure. LIGHT SOURCE POSITIONING The is % tested with a light source that uniformly illuminates the full area of the integrated circuit, 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, and differential stages are cross-coupled. Furthermore, the photodiode area is very large relative to the op amp input circuitry making these effects negligible. I D = I D 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 area and fall only on the op amp circuitry, the would not perform properly. The large (.9 x.9 inch) photodiode area allows easy positioning of narrowly focused light sources. The photodiode area is easily visible it appears very dark compared to the surrounding active circuitry. The incident angle of the light source also affects the apparent sensitivity in uniform irradiance. For small incident angles, the loss in sensitivity is simply due to the smaller effective light gathering area of the photodiode (proportional to the cosine of the angle). At a greater incident angle, light is reflected and scattered by the side of the package. These effects are shown in the typical performance curve Response vs Incident Angle. DARK ERRORS The dark errors in the specification table include all sources. The dominant error source is the input offset voltage of the op amp. Photodiode dark current and input bias current of the op amp are approximately pa and contribute virtually no offset error at room temperature. Dark current and input bias current double for each C above C. At 7 C, the error current can be approximately pa. This would produce a mv offset with = MΩ. The is useful with feedback resistors of MΩ or greater at room temperature. The dark output voltage can be trimmed to zero with the optional circuit shown in Figure 3. EXTERNAL 7Ω C EXT MΩ () MΩ () () 33kΩ 3pF kω 3pF 33kΩ 8pF kω 3pF NOTE: () No C EXT required. FIGURE. Using External Feedback Resistor. C EXT = I D 7

When used with very large feedback resistors, tiny leakage currents on the circuit board can degrade the performance of the. Careful circuit board design and clean assembly procedures will help achieve best performance. A guard trace on the circuit board can help minimize leakage to the critical non-inverting input (pin ). This guard ring should encircle pin and connect to Common, pin 8. DYNAMIC RESPONSE Using the internal resistor, the dynamic response of the photodiode/op amp combination can be modeled as a simple R/C circuit with a 3dB cutoff frequency of khz. This yields a rise time of approximately 9µs (% to 9%). Dynamic response is not limited by op amp slew rate. This is demonstrated by the dynamic response oscilloscope photographs showing virtually identical large-signal and small-signal response. Dynamic response will vary with feedback resistor value as shown in the typical performance curve Voltage Output Responsivity vs Frequency. Rise time (% to 9%) will vary according to the 3dB bandwidth produced by a given feedback resistor value t R. 3 () f C where: t R is the rise time (% to 9%) f C is the 3dB bandwidth LINEARITY PERFORMANCE Current output of the photodiode is very linear with radiant power throughout a wide range. Nonlinearity remains below approximately.% up to µa photodiode current. The photodiode can produce output currents of ma or greater with high radiant power, but nonlinearity increases to several percent in this region. This excellent linearity at high radiant power assumes that the full photodiode area is uniformly illuminated. If the light source is focused to a small area of the photodiode, nonlinearity will occur at lower radiant power. NOISE PERFORMANCE Noise performance of the is determined by the op amp characteristics in conjunction with the feedback components and photodiode capacitance. The typical performance curve Output Noise Voltage vs Measurement Bandwidth shows how the noise varies with 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). The typical performance curve Noise Effective Power vs Measurement Bandwidth shows how NEP varies with and measurement bandwidth. Gain Adjustment +%; % µa / REF 7Ω 7Ω kω kω Ω Ω Ω.µF FIGURE. Responsivity (Gain) Adjustment Circuit. µa / REF Adjust dark output for V. Trim Range: ±7mV FIGURE 3. Dark Error (Offset) Adjustment Circuit. 8

= R + R I D R This used as photodiode, only. NC 7Ω R 9kΩ R kω I D 7Ω NC Advantages: High gain with low resistor values. Less sensitive to circuit board leakage. Disadvantage: Higher offset and noise than by using high value for. FIGURE. T Feedback Network. 7Ω I D = (I D I D ) Bandwidth is reduced to.8khz due to additional photodiode capacitance. Max linear input voltage ().6V typ 7Ω = I D + I D FIGURE 7. Differential Light Measurement. 7Ω = I D FIGURE 6. Summing Output of Two s. 7Ω R I D +V V kω I O ma I O = I D + R FIGURE 8. Current Output Circuit. 9

Output filter reduces output noise from µv to 9µV. 3.3V V Z () 7Ω kω.µf + = I D V Z (pesudo-ground) 7Ω 8 nf 3 FIGURE. Output Filter to Reduce Noise. NOTE: () Zener diode or other shunt regulator. FIGURE 9. Single Power Supply Operation. kω kω INA6 Difference Measurement 7Ω = I D 3 kω kω 6 = ( ) G = kω kω LOG 7 Log of Ratio Measurement (Absorbance) V = K log O 7Ω = I D C C 3 nf FIGURE. Differential Light Measurement.

R 3 kω C.µF A R R C.µF db/decade 7Ω f 3dB = R 3 (πr C ) 8 FIGURE. DC Restoration Rejects Unwanted Steady-State Background Light. / REF µa µa / REF V to 36V 8 3 7Ω N IN8 kω -ma (ma Dark) R.kΩ R 6Ω Calculations shown provide a dark output of ma. Output is ma at a photodiode current of I D max. Values shown are for I D max max = µa.. X 6 R = 99,Ω ( I D max ) R = 6, 6,Ω ( I D max ) FIGURE 3. -ma Current-Loop Transmitter.