TSL245 INFRARED LIGHT-TO-FREQUENCY CONVERTER SOES018 – MAY 1995 D D D D D D D High-Resolution Conversion of Light Intensity to Frequency With No External Components Direct Interface With a Microcontroller Compact Three-Leaded Plastic Package Single-Supply Operation Down to 2.7 V Nonlinearity Error Typically 0.2% at 100 kHz Advanced LinCMOS Technology Integral Visible-Light Cutoff Filter description The TSL245 infrared light-to-frequency converter combines a silicon photodiode and a current-to-frequency converter on a single monolithic CMOS integrated circuit. The output is a square wave (50% duty cycle) with frequency directly proportional to light intensity. Because the output is TTL compatible, it allows direct interface to a microcontroller or other logic circuitry. The device responds over the infrared light range of 800 nm to 1100 nm. The TSL245 is characterized for operation over the temperature range of – 25°C to 70°C. The TSL245 is offered in a black, infrared-transmissive package (see Figure 1). The photodiode area is 1.36 mm2 (0.0029 in2). 2,0 (0.079) T.P.† 0,75 (0.030) 0,65 (0.026) 2,25 (0.089) 1,75 (0.069) 0,635 (0.025) 0,4 (0.016) Pin 1 Pin 2 Pin 3 1,25 (0.049) 0,75 (0.030) GND VDD OUT 1 2 4,0 (0.157) T.P.† 3 1 2 2,05 (0.081) 1,55 (0.061) 0,65 (0.026) 0,55 (0.022) 0,86 (0.034) 0,46 (0.018) 15,7 (0.619) 13,2 (0.520) 3,05 (0.120) 2,55 (0.100) 4,8 (0.189) 4,4 (0.173) 4,85 (0.191) 4,35 (0.171) 0,85 (0.033) 0,35 (0.014) 0,75 (0.030) R 0,51 (0.02) 0,385 (0.015) 3 5,05 (0.199) 4,55 (0.179) 1,75 (0.069) 1,25 (0.049) 4,35 (0.171) 3,85 (0.152) 2,74 (0.108) 2,34 (0.092) † True position when unit is installed. NOTE A: All linear dimensions are in millimeters and parenthetically in inches. Figure 1. TSL245 Packaging Configuration Advanced LinCMOS is a trademark of Texas Instruments Incorporated. Copyright 1995, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TSL245 INFRARED LIGHT-TO-FREQUENCY CONVERTER SOES018 – MAY 1995 functional block diagram Light Current-to-Frequency Converter Photodiode Output absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Supply voltage, VDD (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 V Operating free-air temperature range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 25°C to 70°C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 25°C to 85°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C † Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. NOTE 1: All voltage values are with respect to GND. recommended operating conditions Supply voltage, VDD Operating free-air temperature range, TA MIN NOM 2.7 5 – 25 MAX UNIT 6 V 70 °C electrical characteristics at VDD = 5 V, TA = 25°C (unless otherwise noted) PARAMETER VOH VOL High-level output voltage IDD Supply current TEST CONDITIONS IOH = – 4 mA IOL = 4 mA Low-level output voltage Full-scale frequency‡ MIN 4 TYP MAX 4.3 V 0.17 0.26 2 3 500 kSVS Supply-voltage sensitivity VDD = 5 V ±10% ‡ Full-scale frequency is the maximum operating frequency of the device without saturation. UNIT V mA kHz 0.5 %/ V operating characteristics at VDD = 5 V, TA = 25°C PARAMETER fO TEST CONDITIONS MIN TYP MAX UNIT Output frequency Ee = 920 µW/cm2, λp = 940 nm Ee = 0 200 250 300 kHz 0.25 10 Hz Nonlinearity § fO = 0 kHz to 10 kHz fO = 0 kHz to 100 kHz ± 0.1% %F.S. ± 0.2% %F.S. 1 pulse of new frequency plus 1 µs Step response to full-scale step input ‡ Full-scale frequency is the maximum operating frequency of the device without saturation. § Nonlinearity is defined as the deviation of fO from a straight line between zero and full scale, expressed as a percent of full scale. 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TSL245 INFRARED LIGHT-TO-FREQUENCY CONVERTER SOES018 – MAY 1995 TYPICAL CHARACTERISTICS OUTPUT FREQUENCY vs IRRADIANCE PHOTODIODE SPECTRAL RESPONSIVITY 1000 0.9 TA = 25°C 0.8 Normalized Responsivity fO – Output Frequency – kHz 100 1 VDD = 5 V λp = 940 nm TA = 25°C 10 1 0.1 0.7 0.6 0.5 0.4 0.3 0.2 0.01 0.1 0.001 0.001 0.01 0.1 1 10 10 0 0 600 1k 700 DARK FREQUENCY vs TEMPERATURE 100 fO(dark) – Dark Frequency – Hz VDD = 5 V Ee = 0 10 1 0.1 0 1000 900 1100 Figure 3 25 50 75 Temperature Coefficient of Output Frequency – ppm/ °C Figure 2 0.01 – 25 800 λ – Wavelength – nm Ee – Irradiance – µW/cm2 TA – Temperature – °C TEMPERATURE COEFFICIENT OF OUTPUT FREQUENCY vs WAVELENGTH OF INCIDENT LIGHT 10000 VDD = 5 V TA = 25°C to 70°C 8000 6000 4000 2000 0 700 750 800 850 900 950 1000 λ – Wavelength of Incident Light – nm Figure 4 Figure 5 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TSL245 INFRARED LIGHT-TO-FREQUENCY CONVERTER SOES018 – MAY 1995 TYPICAL CHARACTERISTICS OUTPUT FREQUENCY vs SUPPLY VOLTAGE 1.005 Normalized Output Frequency 1.004 TA = 25°C fO = 500 kHz 1.003 1.002 1.001 1 0.999 0.998 0.997 0.996 0.995 2.5 3 3.5 4 4.5 5 5.5 VDD – Supply Voltage – V Figure 6 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 6 TSL245 INFRARED LIGHT-TO-FREQUENCY CONVERTER SOES018 – MAY 1995 APPLICATION INFORMATION power-supply considerations For optimum device performance, power-supply lines should be decoupled by a 0.01-µF to 0.1-µF capacitor with short leads (see Figure 7). output interface The output of the device is designed to drive a standard TTL or CMOS logic input over short distances. If lines greater than 12 inches are used on the output, a buffer or line driver is recommended. measuring the frequency The choice of interface and measurement techniques depends on the desired resolution and data-acquisition rate. For maximum data-acquisition rate, period-measurement techniques should be used. Period measurement requires using a fast reference clock with available resolution directly related to reference clock rate. The technique measures rapidly varying light levels or provides a fast measurement of a constant light source. Maximum resolution and accuracy can be obtained using frequency-measurement, pulse-accumulation, or integration techniques. Frequency measurements provide the added benefit of averaging random- or high-frequency variations (jitter) resulting from noise in the light signal. Resolution is limited primarily by available counter registers and allowable measurement time. Frequency measurement is well suited for slowly varying or constant light levels and for reading average light levels over short periods of time. Integration, the accumulation of pulses over a very long period of time, can be used to measure exposure – the amount of light present in an area over a given time period. VDD 0.1 µF 2 TSL245 3 1 Timer / Port MCU Figure 7. Typical TSL245 Interface to a Microcontroller POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 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