First Sensor Evaluation Boards Data Sheet Wavelength Sensitive Diodes Part Description WS7.56 PCBA2 US Order 10-044 International Order 5000004 39.4 8.9 5.7 7.6 34.3 0.5 1.62 4X 2.5 4.1 0.7 2.5 5.7 REF CHIP SURFACE 2.5 2.54 0.5 11.1 JUMPER JP1 27.9 22.8 TEMPERATURE SENSOR WAVELENGTH SENSOR 1.8 5X 0.76 ADJUSTABLE GAIN 4.4 PLATED THRU 7.1 6.8 SWITCHES 2.54 TYP FRONTSIDE VIEW BACKSIDE VIEW DESCRIPTION APPLICATIONS RoHS The WS7.56 PCBA2 is a unique wavelength sensor based on silicon photodiode technology. The sensor is constructed Precision photometry 2011/65/EU monolithically by superimposing two photodiodes vertically. The active area is 7.56 mm (2.7 mm X 2.7 mm). This device is Analytical instruments most useful for wavelength de-termination of monochromatic light sources such as lasers and LEDs. More component level Medical equipment information is available on the Wavelength Sensitive Photodiode on data sheet WS7.56 TO5. Wavelength determination for The sensor is mounted on a PCB which contains all of the necessary circuitry to convert incident wavelength to an output monochromatic light voltage. The voltage is proportional to wavelength in the range of 450 nm to 850 nm. The output is independent of intensity. The circuit provides switched gain controls to accommodate various output requirements. As an example a typical output is 1.7 volts for a wavelength of 670 nm, with a gain setting of 5. The data in this sheet provides typical information. The actual output must be calibrated against known sources for accuracy. Resolution of 0.1 nm is possible. The circuit requires 15 volts and consists of two logarithmic amplifiers and a ratio calculator. The sensor is mounted on a temperature sensor for reference. Applications include laser monitoring, matching of LEDs and other light sources. A jumper is provided for optimizing photodiode biasing. Absolute maximum ratings Spectral response 23C Symbol Parameter Min Max Unit T Storage Temp -40 +100 C STG 0.50 T Operating Temp -20 +55 C OP 0.45 Power Supply Voltage ANODE 1 V 12.0 18.0 V S 0.40 Recommended 15V 0.35 I Supply Current 20 - mA S ANODE 2 0.30 V Applied Bias Voltage* 0 10 V R 0.25 Connections 0.20 PIN CONNECTIONS 0.15 TP1 -15V TP2 GND 0.10 TP3 +15V 0.05 TP4 WAVELENGTH OUT 0.00 TP5 TEMP OUT 400 450 500 550 600 650 700 750 800 850 900 950 1000 WAVELENGTH (nm) Electro-optical characteristics 23 C Symbol Characteristic Test conditions Min Typ Max Units --- V Output Voltage -4.5 +6.0 V O I Output Current Limit (Temp sensor) --- --- 10 mA O Input Dynamic Range V = 15 V V = 0 V 0.01 --- 3 mW s R Spectral responsivity Diode 1 = 550 nm --- 0.17 --- A/W Spectral responsivity --- 0.45 --- A/W Diode 2 = 890 nm Rev. 14/02/2018 subject to change without notice www.first-sensor.com contact first-sensor.com Page 1/3 RESPONSIVITY (A/W) LOG AMP 1 WS7.56-TO5 TP4 WAVELENGTH OUT GROUND PIN 1 LOG AMP 1 ADJUSTABLE GAIN JP1 SWITCHES TP5 TEMP OUT TEMPERATURE SENSOR +5 V TP3 +15 V PRECISION +5 V VOLTAGE TP2 GROUND REGULATOR SCHEMATIC DIAGRAM TP1 -15 V APPLICATION NOTES Description The WS7.56 PCBA2 is a circuit board complete with a precision wavelength sensing diode array, a precision temperature sensor and processing circuitry. Two output signals are 1) a voltage output proportional to the wavelength of the light sensed by the photodiode array and 2) a voltage output proportional to the temperature of the case of the photodiode array. The photodiode array is made using silicon technology. The WS7.56 PCBA2 is rated for the wavelength range of 450 nm to 850 nm. It is best suited to determine the wavelength of monochromatic light. Operation The magnitude of the wavelength voltage output is controlled by three slide switches that change the gain amplifier. The gain ranges are shown in table 1. SWITCH POSITIONS ON GAIN ON OFF 5.0 3 1 & 2 3.0 2 1 & 3 1 2 3 1.9 3 & 2 1 1.0 1 3 & 2 Table 1. GAIN ADJUSTMENT Figure 1 shows the typical output voltage versus wavelength for a gain of 5. The voltage out will be relative to the spectral density center. That is, the actual output voltage will be related to the integral of the combination of the spectral response curve and the spectral content of the light input. Assuming the light input is very near a single wavelength (i.e., assuming a good laser source) the voltage out will be a good analog of the wavelength of the light source. Under optimum conditions of light intensity and wavelength spectral resolutions down to 1.0 nm are possible. Detector Characteristics The detector used is the WS7.56 TO5. Please see the WS7.56 TO5 data sheet for specifications for this detector response. Temperature Considerations The WS7.56 PCBA2 operating temperature range is -20 C to +55 C. The wavelength output has a temperature dependence of 1 nm per degree C. Variations in temperature will cause changes to dark currents that can affect accuracy. The circuitry also includes a precision temperature sensor LM35 from National Semiconductor. This sensor allows users to calibrate the wavelength output based on the temperature of the wavelength detector. The temperature sensor output is 10 mV per degree C, and is typically accurate to 0.25 C. The range of the temperature sensor is from +2 C to +150 C. If additional information is needed for the temperature sensor component specifications or circuit suggestions please see the LM35 data sheet on the National Semiconductor website. Detector Bias The circuitry provides a jumper JP1, to allow either a zero volt bias or an internal 5 volt bias to the photodiode array. The zero volt bias eliminates dark currents from the photodiode array, enabling better results over varying temperatures. The 5 volt bias slightly extends the NIR performance range and increases frequency response. For bias options other than 0 V and 5 V, remove the jumper and connect an external bias supply directly to the center pin JP1. Frequency Response The amplifier used is a logarithmic amplifier and consequently the frequency response is a function of the input signal amplitude. For typical input signals in the 0.5 milliwatt range and wavelengths in the range of 450 nm to 850 nm the -3db frequency response will be approximately 10 KHz with the 5 V bias option engaged. Rev. 14/02/2018 subject to change without notice www.first-sensor.com contact first-sensor.com Page 2/3