LX1970 Mini Control Board I N T E G R A T E D LX1970 Light Sensor P R O D U C T S SCHEMATIC WWW . Microsemi .C OM C1 0.1µF 1 R3 VDD 8 VSS VDD R1 NC NC NC NC 6 3 4 VOUT GND 7 2 5 SOURCE SINK LX1970DU R2 C2 4.7µF PHOTO The LX1970 Mini Light Sensor Board can be used to convert a manual DC voltage dimmer to a closed loop automatic dimmer. The resistor values can be changed to fit the design requirements. The LX1970 output current is proportional to the incident light intensity up to the point where either the current source voltage compliance is exceeded or the light sensor saturates. See the data sheet and application note for additional information. V OUT = [(I SRC × R1 ) + V DD ]× R2 R1 + R2 PACKAGE PIN OUT The value of R3 is typically less than 1K and is used as a power filter for the LX1970 if the VDD line is excessively noisy. With VDD = 3.0V, R1 = 150K, R2 = 30K and R3 = 0, the current output voltage in total darkness is VDD x R2/ (R1 + R2) = 0.5V. The maximum output voltage is approximately VDD – 0.3 = 2.7V, which is limited by the output voltage compliance at a current of 2.7V x (R1 + R2) / (R1 x R2) = 108uA. VDD active area 1 2 7 NC NC 3 6 NC SRC 4 5 SNK (Top View) FUNCTIONAL PIN DESCRIPTION 1/27/2005 Rev 1.0a DESCRIPTION Input Supply Voltage (Some boards wired with a RED pigtail.) VSS Ground Reference for Power and Signal Output (Some boards wired with a BLACK pigtail.) SNK Output Current Sink SRC Output Current Source (Some boards wired with a YELLOW pigtail.) Microsemi Integrated Products 11861 Western Avenue, Garden Grove CA. 92841 714-898-8121, FAX: 714-893-2570 LX1970 DU PACKAGE VDD VSS NC Protected by U.S. Patents: 6,787,757; Patents Pending. NAME 8