Power Supply Input/Output Power Supply Input (VCC) Verify VCC is between 4.75 VDCand 5.25 VDC at test point DC-DC Converter Output (VDD) Verify VDD is between 3.05 VDC and 3.55 VDC at test TP-Y IR Emitter/Detector IR Emitter Voltage Drop Verify VD is between 0.67VDC and 1.47 VDC at maximum operation point IR Emitter Sink Current Verify maximum current through IR Emitter is between 20 mA and 120 mA Note: Remove jumper for current measurement IR Detector Voltage Drop Verify minimum voltage drop across Detector Diode is 0.67 VDC Verify maximum voltage drop across Detector Diode is 1.8 VDC IR Detector Source Current Verify detector current is between less than 100µA Automatic Gain Circuit Verification of AGC Input reference voltage of 0.5 VDC and verify AGC output increases to maximum gain (2) Input reference voltage of 1.25 VDC and verify AGC output decreases to minimum gain (1) Generally speaking there are three modes of operation which are of relative importance when using photodiodes. They include the photovoltaic mode and photoconductive mode, each having specific benefits. The highest sensitivity can be obtained in the photovoltaic mode of operation, and with null biasing; the dark current offset is negligible. In this mode the detection, incident infrared or ambient light reacts with the photo-sensitive junction of the semiconductor, producing a potential across the device. This potential varies between manufactures but is typically between 0.6 VDC and 1.2 VDC. While this configuration is generally sufficient for most applications it is usually slower than the photoconductive mode. The photoconductive mode is faster but unlike the photovoltaic mode its dark current leakage is not optimal and therefore affects sensitivity. In the simulation circuit below the current source is acting like a photodiode (in conductive mode) which drives the differential input of the amplifier. The static gain of the amplifier is approximately 1.5. Graph 1 below shows the incident current verse voltage of the photodiode, while not obstructed the photodiode will maintain a constant slope before reaching saturation. The midpoint linear region can be used as a reference point for a digital transceiver. This would effectively couple the two systems together and therefore create the detection portion of the speed sensor. The voltage reference
Power Supply Input/Output Power Supply Input (VCC) Verify VCC is between 4.75 VDCand 5.25 VDC at test point DC-DC Converter Output (VDD) Verify VDD is between 3.05 VDC and 3.55 VDC at test TP-Y IR Emitter/Detector IR Emitter Voltage Drop Verify VD is between 0.67VDC and 1.47 VDC at maximum operation point IR Emitter Sink Current Verify maximum current through IR Emitter is between 20 mA and 120 mA Note: Remove jumper for current measurement IR Detector Voltage Drop Verify minimum voltage drop across Detector Diode is 0.67 VDC Verify maximum voltage drop across Detector Diode is 1.8 VDC IR Detector Source Current Verify detector current is between less than 100µA Automatic Gain Circuit Verification of AGC Input reference voltage of 0.5 VDC and verify AGC output increases to maximum gain (2) Input reference voltage of 1.25 VDC and verify AGC output decreases to minimum gain (1) Generally speaking there are three modes of operation which are of relative importance when using photodiodes. They include the photovoltaic mode and photoconductive mode, each having specific benefits. The highest sensitivity can be obtained in the photovoltaic mode of operation, and with null biasing; the dark current offset is negligible. In this mode the detection, incident infrared or ambient light reacts with the photo-sensitive junction of the semiconductor, producing a potential across the device. This potential varies between manufactures but is typically between 0.6 VDC and 1.2 VDC. While this configuration is generally sufficient for most applications it is usually slower than the photoconductive mode. The photoconductive mode is faster but unlike the photovoltaic mode its dark current leakage is not optimal and therefore affects sensitivity. In the simulation circuit below the current source is acting like a photodiode (in conductive mode) which drives the differential input of the amplifier. The static gain of the amplifier is approximately 1.5. Graph 1 below shows the incident current verse voltage of the photodiode, while not obstructed the photodiode will maintain a constant slope before reaching saturation. The midpoint linear region can be used as a reference point for a digital transceiver. This would effectively couple the two systems together and therefore create the detection portion of the speed sensor. The voltage reference
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