lx1970 mini control board 1/27/2005 microsemi rev 1.0a integrated products 11861 western avenue, garden grove ca . 92841 714-898-8121, fax: 714-893-2570 www. microsemi . com lx1970 light sensor integrated products schematic r3 vdd r1 r2 c2 4.7f vout gnd c1 0.1f lx1970du vdd nc nc source sink nc nc vss 1 2 3 4 5 6 7 8 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 complia nce is exceeded or the light sensor saturates. see the data sheet and application note for additional information. () [] r2 r1 r2 v r1 i v dd src 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. protected by u.s. patents: 6,787,757; patents pending. photo package pin out vss nc nc snk vdd nc nc src 1 2 3 5 4 6 7 8 active area du p ackage (top view) functional pin description n ame d escription v dd input supply voltage (some boar ds wired with a red pigtail.) v ss 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.) l l x x 1 1 9 9 7 7 0 0
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