First Sensor Evaluation Boards Data Sheet Dual Axis PSD with Sum and Difference Amplifier Part Description DL400-7 PCBA US Order 10-034 International Order 5000014 57.2 50.8 PSD C 0.50 1.57 L 27.18 3.2 1.00 CHIP SURFACE 2X 2.54 TOOLING HOLE 38.1 X- C Y- 44.5 PSD L Y+ 0.50 X+ 19.39 1.9 1 2 3 4 5 6 7 8 9 2.1 3.2 2.54 TYP 14.4 2 ACTIVE AREA = 400 mm (20 mm X 20 mm) 22.9 11.4 TOP VIEW 6.3 Description Applications RoHS 2011/65/EU NIR & visible pulsed light The DL400-7 PCBA is a 20 mm X 20 mm dual axis position sensing diode on a PCB with sum and difference positioning and tracking amplifiers. It also contains circuitry for applying a 14.3 V bias voltage to the position sensing diode, or the user Laser beam tracking can externally apply a bias voltage. The board has a 9 pin connector attached for easy hook up. Outputs are bipolar voltage analogs of the X and Y position of the light spot centroid, as well as the total X current and the total Y current. The sum outputs may be used to externally normalize the X and Y difference outputs. By normalizing the X and Y signals, they become independent of fluctuations in light spot intensity. Absolute maximum ratings Spectral response 22C Symbol Parameter Min Max Unit 0.70 T Storage Temp -15 +100 C STG T Operating Temp 0 +70 C OP 0.60 Power Supply Voltage V 10 18 V S Recommended 15V 0.50 V Applied Bias Voltage* 0 10 V R 0.40 Connections PIN CONNECTIONS 0.30 FUNCTION PIN 1 NEGATIVE BIAS VOLTAGE TO PSD 2 POSITIVE BIAS VOLTAGE TO PSD 0.20 3 Y AXIS VOLTAGE OUT- BIPOLAR 4 X AXIS VOLTAGE OUT- BIPOLAR 0.10 5 ANODE SUM (Y AXIS)- POSITIVE CATHODE SUM (X AXIS)- NEGATIVE 6 7 +15 V SUPPLY VOLTAGE 0.00 300 400 500 600 700 800 900 1000 1100 8 SIGNAL & POWER COMMON 9 -15 V SUPPLY VOLTAGE WAVELENGTH (nm) Electro-optical characteristics 22 C Symbol Characteristic Test conditions Min Typ Max Units I Output Current Limit V = 15 V V = 0 V --- --- 25 mA O s R Theoretical noise V = 15 V V = 0 V --- 15 --- nV/Hz s R Bandwidth** V = 15 V V = 10 V = 880 nm --- 200 --- kHz -3dB s R Resolution** V = 15 V V = 10 V = 880 nm 1.0 --- --- m s R Linearity** V = 15 V V = 10 V = 880 nm --- 1 --- % of full scale s R Maximum light intensity --- --- 1.5 W/cm V = 15 V V = 10 V = 880 nm s R * actual bias voltage to photodiode: pad 1 voltage times 0.95. ** dependant on bias voltage Rev. 14/02/2018 subject to change without notice www.first-sensor.com contact first-sensor.com Page 1/3 RESPONSIVITY (A/W)- PHOTODIODE BIAS (OPTIONAL) PIN 1 CATHODE 1 ANODE 1 J1 -15 V V(y) DIFFERENCE PIN 3 DIFF CATHODE 2 ANODE 2 V(y) SUM PIN 5 SUM DL400-7-CER +15 V +15 V PIN 7 -15 V -15 V PIN 9 AGND ANALOG GROUND PIN 8 V(x) DIFFERENCE PIN 4 DIFF V(x) SUM PIN 6 SUM + PHOTODIODE BIAS (OPTIONAL) PIN 2 BLOCK DIAGRAM J2 +15 V APPLICATION NOTES Description The DL400-7 PCBA is a duolateral position sensing module composed of a 20 mm X 20 mm active area position sensing photodiode and associated circuitry. It senses the position of a light spot on the surface of the photodiode and provides the voltage analogs of the X, Y and spot intensity. The sensing diode is made using silicon technology and consequently responds to light wavelengths between 400 nm and 1100 nm. The output, as a function of wavelength, follows our typical -7 process silicon photodiode responsivity curve. PSDs Duolateral position sensing diodes are photodiodes with electrodes placed at the edges of the photodiode. Two resistive sheets cover the pn junction, with one sheet on top and one sheet on the bottom. As light impinges on the photodiode, the pn junction generates a current at the centroid of the light power density. The current from this generator separates at the top resistive sheet according to Ohms law, and electrodes at opposite ends collect the individual currents. The response at the bottom sheet layer is similar to the top sheet except that the current is in the opposite direction. The bottom electrodes are placed at edges orthogonal to the top electrodes. Outputs The DL400-7 PCBA module contains amplifiers that convert the light generated currents into voltages. The voltages are then processed to provide a bipolar signal for the X axis and a bipolar signal for the Y axis. The currents are further processed to provide a voltage for the total X current and the total Y current. These voltages represent the light intensity. Note: the X SUM output voltage is negative, the Y SUM is positive. PSD Biasing Position sensing diodes of the type used in the DL400-7 PCBA module are more accurate if a reverse bias is applied across the diode. Installing jumpers J1 and J2 will engage circuitry that uses the supply voltage to create and apply a reverse bias of ~95% of the supply voltage (14.3 volts with a +/-15 V supply). In this configuration, there should be no connection to Pins 1 and 2. For bias voltages other than 14.3 volts, remove jumpers J1 and J2 and hook up an external bias source to Pins 1 and 2. (For zero bias operation, just remove jumpers. No connection is necessary to Pins 1 and 2). Although reduced bias will degrade the linearity performance of the PSD, voltage offset and noise can be improved. Determining the optimum bias voltage for each application is usually a trial and error procedure. If determining positions over a large area of the PSD is required, the built-in 14.3 volts bias is probably the best option. If low light levels and/or small incremental movement over a small area of the PSD are the application, then zero to low bias voltage may work best. Effects of Light Spot Shape, Size and Intensity Since the photodiode current appears to be generated at the centroid of the light spot power density, it is the centroid location that is tracked by the voltage outputs. If any of the light spot is off the photodiode then the centroid of the light that does fall in the photodiode is the location tracked. The ultimate resolution of the position sensor is signal to noise limited. Consequently, the spot intensity should be as great as possible without causing damage to the photodiode. There is a limit to the intensity. The spot size and intensity should not concentrate the beam such that the light power locally heats the detector surface above 110 C. In practice the light intensity should never exceed 1.5 W/cm. Many applications use an intensity of 1 to 3 milliwatts for a spot size of 1 mm. The current outputs of the photodiode are dependant on the light intensity and as a result the voltage outputs are also dependant on light intensity. If the beam source changes intensity when the spot location is being sensed, then the output should be normalized using the sum signals available on the DL400-7 PCBA. Normalization is accomplished externally by dividing the location voltage by the sum voltage for the layer (X or Y) being measured. The DL400-7 PCBA does not normalize the location output signals. Rev. 14/02/2018 subject to change without notice www.first-sensor.com contact first-sensor.com Page 2/3