lx1971 evaluation board user?s guide lx1971 visible light sensor integrated products
lx1971 e valuation b oard u ser g uide copyright ? 2003 microsemi page 2 rev. 1.0a 12/3/03 integrated products 11861 western avenue, garden grove , ca. 92841, 714-898-8121, fax: 714-893-2570 t able o f c ontents overview ............................................................................................................................... ......................................3 features operation t ables evaluation boar d connections .................................................................................................. ............ 4 jumper ex planat ion............................................................................................................ ..................... 4 test point descripti ons....................................................................................................... .................... 4 f igures lx1971 evaluation boar d component list......................................................................................... ... 5 lx1971 evaluation board silk screen & p cb tra ces........................................................................... 5 lx1971 evaluation bo ard sche matic .............................................................................................. ....... 6
lx1971 e valuation b oard u ser g uide copyright ? 2003 microsemi page 3 rev. 1.0a 12/3/03 integrated products 11861 western avenue, garden grove , ca. 92841, 714-898-8121, fax: 714-893-2570 o verview the lx1971 is a new technology light sensor with spectral response that emulates the human eye. this device is ideal for monitoring ambient light for the control of ar tificial lighting, operation of shades, led signage and display, street lighting, automotive light sensors and control of backlight dimming. it has a unique photo diode arrangement (patents pending) with a peak response at 520nm while sharply attenuating both ultra violet and infrared wavelengths without the use of an optical filter. the evaluation board ships with an aperture wheel that allows the user to approximate the sensor?s mounting inside an assembly with an entrance hole for light. the aperture wheel can rotate to program various holes sizes. three small rheostats and four input connection terminals permit the sensor?s output gain (current to voltage conversion) and dimming transfer function to be adjusted to the user?s ambient light conditions, and output voltage requirements. for a quick demonstration of the dimming capability of the sensor the evaluation board can be configured (by setting j1 to the led driver position, and j4 to the driver position) to power two white led?s by a microsemi lx1990 led sink driver controller (included) when 3 to 5v is connected across vdd and gnd terminals. evaluation board features ? aperture wheel allows simulation of sensor mounting inside a case ? included rheostats allows easy output voltage gain conversion for light level ? additional jumpers enable isolation, and pull-down diodes for some configurations ? included lx1990 sink led driver and two microsemi white led?s demonstrate the sensors utility and ease of use e valuation b oard o peration the evaluation board has five possible inputs of which at least two must be used to operate the circuit. in the simplest configuration connect 3v to 5v across vdd and gnd. with this power connected and all jumpers in their open position (see evaluation board schematic figure 2) the lx1971 by itself can be evaluated. the src and snk outputs will act as a current source and sink respectively and change with the intensity of light. the output compliance range will of course depend on the input voltage and output current (see lx1971 datasheet for details). if the light sensors current outputs are to be used directly, then the src and snk terminals can be used to hook up external circuitry to the sensor. if however the application requires conversion of the output currents to a scalable voltage output, then j2 and/or j4 should be used. jumper j2 when set to the divider position connects the src output to external resistors. when jumper j4 is connected in the snk pull-up position then the snk output current can be pulled up to vdd or some lower external voltage. jumper j3 when in the d2 in position inserts an isolation diode in series with the divider string for applications where the sensor may be disengaged for full manual override. this could be true if power to the sensors is interrupted, or the src diode pull- down terminal is set low shunting the sensors output current. the src adjust pull-up terminal allows an external dc voltage or pwm signal to connect to the high side of the voltage divider r1+r2 and r4+r5. rheostats r1 and r4 allow easy adjustment of the divider; they are set to their maximum (100k ? ) when set fully clockwise. the src fixed pull-up terminal provides a second input for a dc voltage or pwm signal for more complex signal conditioning circuits. the terminal labeled src diode pull-down can be used as described above to shunt the sensors current; this too could be a dc voltage or pwm signal. on the snk side the evaluation board includes one 100k ? rheostat, r6 that can be connected to vdd to generate a signal inverted from the src output side. on both the src and snk output a 1uf capacitor (c1 & c3) is placed in parallel with the output resistors. the capacitors slow down the response time of the sensor so it won?t try to track the 50-60hz lighting. all evaluation board input connections; jumpers and test points are summarized in table 1-3 on the following page. see lx1971 datasheet for application schematics and suggestions.
lx1971 e valuation b oard u ser g uide copyright ? 2003 microsemi page 4 rev. 1.0a 12/3/03 integrated products 11861 western avenue, garden grove , ca. 92841, 714-898-8121, fax: 714-893-2570 input allowable range description vdd 3 to 5.5v lx1971 power supply if j1 is set to lx1971 only, or lx1971 power supply and lx1990 and external led?s power supply if j1 is connected to led driver (led?s w ill only light if j4 is also in driver position. gnd 0v common ground reference src diode pull-down 5v to gnd, fixed dc voltage or pwm/logic signal this diode connection is generally used to shunt src output current when disengaging the sensor in a full manual mode src adjust pull-up 5v to gnd, fixed dc voltage or pwm/logic signal first pull-up connection is generally used to set a minimum output voltage or adjust output transfer slope for src pin src fixed pull-up 5v to gnd, fixed dc voltage or pwm/logic signal second pull-up connection is generally used to set a minimum output voltage or adjust output transfer slope for src pin snk pull- up 5v to gnd, fixed dc voltage or pwm/logic signal this pull-up connection is generally used to set a maximum output voltage or adjust output transfer slope for snk pin table 1 ? evaluation board terminals jumper function j1 jumper to led driver connects lx1990 driver ic & lx1971 to vdd, jumper to lx1971 only connects vdd to the lx1971 sensor only. j2 jumper to src open disconnects external divi der circuitry from lx1971 src pin. jumper to divider connects external divider circuitry to src pin. j3 shorts or leaves connect the series diode d2 from src pull-down path j4 jumper to driver connects the snk output to the iset input of the lx1990 through a 4.12k resistor. jumper to sn k pull-up connects the snk pin to the snk pull-up external board connection table 2 ? jumper explanation test point description gnd common ground reference vdd vdd input to lx1971 (3 to 5.5v) snk lx1971 snk output src lx1971 src output src diode pull-down cathode of diode connected to src pin src adjust pull-up 100k rheostat and series 10k resistor to src src fixed pull-up 50k series resistor to src snk pull-up 100k rheostat and parallel 1f capacitor to snk table 3 ? terminal/test point descriptions
lx1971 e valuation b oard u ser g uide copyright ? 2003 microsemi page 5 rev. 1.0a 12/3/03 integrated products 11861 western avenue, garden grove , ca. 92841, 714-898-8121, fax: 714-893-2570 lx1971 evaluation board component list miscellaneous components part description manufacturer & part # reference designators qty ic, sensor m icrosemi lx1971ilm u1 1 ic, controller m icrosemi lx1990i u2 1 diodes v arious 1n4148 d1,d2 2 leds, white bright microsemi upwled470a optomite or equivalent led1 , led2 2 terminals/probe standoffs various 9 capacitors part description manufacturer & part # reference designators qty capacitor, x7r, 100nf, 50v, 10% any c2 1 capacitor, x7r, 1uf, 50v, 10% any c1, c2 2 resistors part description manufacturer & part # reference designators qty resistor, pot thumbwheel 100k any r1,r2,r6 3 resistor, 4.12k, 1%, 1/16w any r7 1 resistor, 10k, 1%, 1/16w any r1,r5 2 resistor, 50.0k, 1%, 1/16w any r3 1 lx1971 evaluation board silk screen & pcb traces* bottom src adjust led-upw lx1990 adjust src top led driver light sensor lx1971 0.8mm 1.0mm 1.2mm 1.5mm 1.75mm 2.0mm d2 out d2 in lx1971 only divider src open 2.5mm dark 2 adjust snk 2 2 evaluation board lx1971 (800) 877-6458 microsemi pull-up driver snk aperture's u2 snk gnd0 vdd j1 c2 led2 led1 j4 r7 r5 c3 r4 2 sensor light diode pull down r6 2 2 sensor light snk pull-up c1 src0 d2 src j2 d1 j3 gnd src fixed u1 r3 r2 r1 2 2 2 sensor light src adj. bottom src adjust led-upw lx1990 adjust src top led driver light sensor lx1971 d2 out d2 in lx1971 only divider src open 2 adjust snk 2 2 evaluation board lx1971 (800) 877-6458 microsemi pull-up driver snk aperture's u2 snk gnd0 vdd j1 c2 led2 led1 j4 r7 r5 c3 r4 2 sensor light led driver diode pull down r6 2 2 sensor light led driver snk pull-up c1 src0 d2 src j2 d1 j3 gnd src fixed u1 r3 r2 r1 2 2 2 sensor light led driver src adj. battery gnd blk vdd red sge3010 x figure 1 * the lx1971 evaluation board shares the same pc b as the lx1970 evaluation board. although the pcb silkscreen may read lx1970, an additional label should indicate that the board is indeed a lx1971 evaluation board and that the lx1971 visible light sensor has been mounted in the sensor position.
lx1971 e valuation b oard u ser g uide copyright ? 2003 microsemi page 6 rev. 1.0a 12/3/03 integrated products 11861 western avenue, garden grove , ca. 92841, 714-898-8121, fax: 714-893-2570 lx1971 evaluation board schematic vdd gnd lx1971idu r3 50k r5 10.0k snk adjust r6 100k c1 1.0 f n/c vdd n/c src gnd n/c snk 1 2 3 45 6 7 8 d1 in4148 d2 1n4148 src bottom adjust r 4 100k r2 10.0k src top adjust r1 100k gnd snk snk pull-up src adj pull-up src fixed pull-up src diode pull-down d2 in d2 out c3 1.0 f j2 j1 j4 r7 4.12k iset gnd i outa i outb lx1990ilm src 2 1 3 6 4 5 j3 c4 0.1 f driver snk pull-up src open divider lx1971 only led driver led1 led2 n/c figure 2 ? schematic
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