microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products description the lx1971 is a new technology light sensor with spectral response that emulates the human eye; it is pin to pin compatible to microsemi?s lx1970 visible light sensor however with a wider dynamic range. this device is ideal for monitoring ambient light for the control of artificial 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. the photo sensor is a pin diode array with an accurate and very repeatable current output. photo current is first multiplied by an integrated high gain amplifier then the square root is taken of the product of the amplifier and an internal reference current. finally this is further multiplied converted to current and made available at two output pins; one a current source and the other a current sink. these currents can easily be converted to voltage by adding a single resistor at either or both outputs. voltage gain is determined by the resistor value typically in the 5k to 50k range. with accurate internal gain amplifiers and square root transfer function, design complexity and cost are greatly reduced. the lx1971 is available in the clear 8- pin msop package. important: for the most current data, consult microsemi ?s website: http://www.microsemi.com protected by u.s. patents: 6,787,757; patents pending key features ? approximate human eye spectral response ? low ir sensitivity ? highly accurate & repeatable output current vs. light ? square root transfer function ? temperature stable ? integrated high gain photo current amplifiers ? complementary current outputs ? no optical filters needed benifits ? requires no wavelength filters ? insensitive to uv and ir ? more than 4 decades usable light range ? enables accurate lighting control systems product highlight snk src ambient light v out v dd gnd 0.45v typ 0.60v typ 25k 4.7uf lx1971 v dd 25k 4.7uf snk src package order info du plastic msop 8-pin t a ( c) rohs compliant / pb-free -40 to 85 lx1971idu note: available in tape & reel. append the letters ?tr? to the part number. (i.e. LX1971IDU-TR) l l x x 1 1 9 9 7 7 1 1
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products absolute maximum ratings v dd ................................................................................................................. -0.3 to 6 v dc snk/src (output complianc e voltage)........................................... -0.3 to v dd + 0.3v dc snk/src (maximum output cu rrent)................................................... intern ally limited operating temperature range ........................................................................ - 40 to +85c storage temperature ra nge.......................................................................... -40 to +100c solder reflow peak temperat ure (soldering 10 seconds ) ......................................... 240 c notes: exceeding these ratings could cause damage to th e device. all voltages are with respect to ground. currents are positive into, ne gative out of specified terminal. solder reflow to follow: ipc/jedec j-std-020b 7/02 pb-sn small body profile thermal data du plastic msop 8-pin thermal resistance - junction to a mbient , ja 206 c/w thermal resistance - junction to c ase , jc 39 c/w package pin out vss nc nc snk vdd nc nc src 1 2 3 5 4 6 7 8 du p ackage (top view) 1 2 3 4 5 6 7 8 1971 xxxx du p ackage (bottom view) xxxx = denotes date code / lot information rohs / pb-free gold lead finish msl 2 / 260c / 1 year functional pin description n ame d escription v dd input supply voltage v ss ground reference for power and signal output snk output current sink src output current source simplified block diagram package photo v dd v ss snk src p p a a c c k k a a g g e e d d a a t t a a
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products recommended operating conditions lx1971 parameter min typ max units supply voltage (v dd ) 31 5.5 v snk compliance voltage range v ss +0.6 v dd v src compliance voltage range v ss v dd - 0.75 v snk/src output resistor range 5 100 k ? 1outputs are functional down to v dd =2.7v electrical characteristics unless otherwise specified, the following specifications apply over the operating ambient temperature -40 c t a 85 c, v dd = 3v to 5.5v, r load = 25kohms, direct light input2 of 584w/cm 2 except where otherwise noted. performance between -40c and 0c and between 70c and 85c are assured by design and characterization. lx1971 parameter symbol test conditions min typ max units supply voltage range v dd 3 5.5 v dc input supply current i dd v dd = 3.0v, i src = 62a, i snk = open 350 590 750 a i src v dd = 3.0v, direct light input of 584w/cm 2 @ 25c 55 61 67 a i src v dd = 3.0v, direct light input of 584w/cm 2 52 61 70 i snk v dd = 3.0v, direct light input of 584w/cm 2 -70 -61 -52 a i src v dd = 3.0v, direct light input of 292w/cm 2 34 41 48 a output current i src v dd = 3.0v, direct light input of 9.34w/cm 2 5.5 7 8.5 a output snk/src current matching i match v dd = 3.0v 2 6 % snk minimum compliance voltage snk vmin v dd = 3.0v, @ 95% of nominal output current v ss +0.45 v ss +0.6 v src maximum compliance voltage src vmax v dd = 3.0v, @ 95% of nominal output current v dd ? 0.6 v dd ? 0.7 v snk/src output dark current i dark3.0v v dd = 3v, no light, 25c 150 400 na snk/src output dark current i dark3.0v v dd = 3v, no light, -40c to 70c 450 1000 na snk/src output dark current i dark3.0v v dd = 3v, no light, 85c 550 1150 na snk/src output dark current i dark5.5v v dd = 5.5v, no light, 25c 320 na wavelength of peak sensitivity ps 520 nm half reception angle ? 60 deg supply voltage coefficient of output current psrr v dd = 3v to 5.5v 2.9 3.5 %/v resolution limit due to random noise i min minimum usable resolution 146 nw/cm 2 sensitivity change @ 910nm i src ? ir current responsivity change with additional direct light input of 584w/cm 2 at 910nm, t a = 25c, v dd = 3v -10 0 10 % of peak radiant sensitive area a photodiode area .369 mm 2 2the input irradiance is supplied from a white light-e mitting diode (led) optical source adjusted to impose 584w/cm 2 at 555nm on the sensor?s surface. e e l l e e c c t t r r i i c c a a l l s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products application information the lx1971 is a light sensor with a spectral response that resembles the human visual system. it is packaged in clear msop package with the same pin out and same supply voltage range as microsemi?s lx1970 light sensor. the lx1971 responsiveness however differs from that of the lx1970. in general the lx1971 has lower sensitivity and a wider dynamic range. whereas the lx1970 has a responsiveness that is directly proportional to the intensity of light falling on the photo receptors. there are two different response equations for the lx1971 depending on the operating range (intensity of the light). below 2500 lux, the response resembles a square root function. above 2500 lux, the response fits a straight line curve. ( ) a l i out 1 . 1 808 . + = for l < 2500 lux () a a l i out 23 0083 . + = for 2500 lux < l < 20000 lux the lx1970 is best suited for applications where the light sensor is an integral part of a continuous lighting control system. for example, in an lcd backlighting application, the level of brightness of the backlight should be adjusted in proportion to the level of ambient lighting; the lx1970 can prov ide closed loop brightness control for this type of system. for most indoor applications, the 2500 lux saturation point of the lx1970 is usually not a limiting affect. the lx1971 is best suited for applications where the system must respond to external events that affect the user?s ability to see clearly. for example, a sensor to turn on headlights or a sensor to adjust the reflectivity of a rear view mirrors. these systems require the sensor to have dynamic range similar to sight. like the human eye, the square root function of the lx1971 makes it extra sensitive to small changes at lower light levels. the wide dynamic range allows the lx1971 to sense the difference between twilight and daylight or sunshine and heavy cloud cover. the following curves show the calculated responsiveness o f the lx1971 without load resistors based on the formulas above. they can be used as baseline guidelines to calculate gain setting resistors. the compliance of the current source output may result in premature saturation of the output when load resistors are added. the src compliance voltage is specified typically at vdd-600mv @ about 4000 lux. lx1971 calculated src full range response 0 50 100 150 200 250 0 5000 10000 15000 20000 25000 incandescent light (lux) src current (a) <2500 lux formula >2500 lux formula lx1971 calculated src low level response 0 10 20 30 40 50 0 500 1000 1500 2000 2500 incandescent light (lux) src current (a) <2500 lux formula lx1971 calculated src high level response 0 50 100 150 200 250 0 5000 10000 15000 20000 25000 incandescent light (lux) src current (a) >2500 lux formula a a p p p p l l i i c c a a t t i i o o n n s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products application examples the following examples present both fully automatic (no user input) and semi-automatic, to fully manual override implementations. these general guidelines are applicable to a wide variety of potential light control applications. the lx1971 can be used fo r the control of artificial lighting, operation of shades, led signage and display, street lighting, automotive light sensors and control of backlight dimming . in each specific application it is important to recognize the need to correlate the si nk and source current of the lx1971 for the target environment and its ambient light conditions. the mechanical m ounting of the sensor, light aperture hole size, use of a light pipe or bezel are critical in determining the response of the lx1971 for a given exposure of light. r1 r2 c1 10f 3v led driver controller or dimming controller input n/c 3.3v or 5v vss vdd src snk figure 1 the example in figure one shows a fully automatic lighting control solution with no user interaction. choose r1 and r2 values for any desired minimum brightness and slope. choose c1 to adjust response time. as an example, let?s say you wish to generate an output voltage from 0.25v to 1.25v to drive the input of an led driver controller. the 0.25v represents the minimum led brightness and 1.25v represent the maximum. the first step would be to determine the ratio of r1 and r2. r1 = r2 [ 3.0v/0.25v ?1] = 11 * r2 next the value of r2 can be calculated based on the maximum output source current coming from the lx1971 under the application?s maximum light exposure, lets say this has been determined to be about 50ua . thus r2 can be calculated first order as follows: r2 = [ 1.25v / 50ua ] = 25k ? r1 = 11 * r2 = 275k ? the output node will actually reach 1.25v when the source current from the lx1971 is only about 44ua since about 6ua of current will be contributed from r1. we are assuming a high impedance input to the led driver. in figure 2 user adjustable bias control has been added to allow control over the minimum and maximum output voltage. this allows the user to adjust the output brightness to personal preference over a limited range. the pwm input source could of course be replaced with an equivalent dc voltage. r1 40k r2 25k 10f led driver controller or dimming controller input n/c 3.3v or 5v vss vdd src snk 3.3v pwm figure 2 figure 3 shows how a fully manual override can be quickly added to the example in figure 2. in addition to the gate to turn on and off the lx1971, a diode has been inserted to isolate the lx1971 when it is shut down. 30k 30k 10f led driver controller or dimming controller input n/c vss vdd src snk pwm cmos gate 60k 3.3v diable control figure 3 the preceding examples represen t just a few of the many ways the sensor can be used. fo r example since there is also a complimentary sink output a resistor from vdd to snk could develop a voltage that could be compared (with some hysteresis) to a fixed (or adjustable) reference voltage and develop a logic signal. in th e case of street lighting or operation of shades such a signal would engage the function when reaching the correct ambient light level. a a p p p p l l i i c c a a t t i i o o n n s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products response vs wavelength i src step response 0 2 4 6 8 10 12 14 16 0 0.5 1 1.5 2 time (seconds) amplitude (w/cm 2 ) v dd = 3.0v; r src = 25k & 4.7uf line regulation dark current vs temp 19 19.5 20 20.5 21 21.5 22 33.544.555.5 vdd (v) src current (a) v dd = 3.5v; r src = 25k & 4.7uf 1 10 100 1000 -40 -20 0 20 40 60 80 100 temperature (oc) dark current (na) 3v 5v 5.5v r src = 25k & 4.7uf snk output psrr gain vs temp 30 40 50 60 70 1 10 100 1000 10000 100000 frequency (hz) psrr (db) v dd = 3.0v; r snk = 25k & 4.7uf 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 -50 0 50 100 temperature (oc) gain/gain(25oc) y = 1.35e-03x + 9.64e-01 v dd = 3.0v direct light input of 13.14w/cm 2 c c h h a a r r t t s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 7 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products snk compliance vs current src compliance vs current 0 20 40 60 80 100 120 0.1 0.2 0.3 0.4 0.5 snk com pliance voltage (v) output current (a) v dd = 3.0v; r snk = 25k & 4.7f 0 20 40 60 80 100 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 source com pliance voltage (vdd-src) output current (a) v dd = 3.0v; r src = 25k & 4.7f src output vs luminance(lux) src output vs luminance(lux) 0 40 80 120 160 0 3000 6000 9000 12000 15000 18000 luminance (lux) src (ua ) incandescent v dd = 4.0v; r snk = 10k & 4.7f 0 10 20 30 40 50 0 500 1000 1500 2000 2500 luminance (lux) src (ua ) incandescent v dd = 4.0v; r snk = 10k & 4.7 c c h h a a r r t t s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 8 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products package dimensions du 8-pin miniature shrink outline package (msop) a1 l e l1 e1 b e s a d c top view side views m illimeters i nches dim min max min max a ? 1.10 ? 0.043 a1 0.05 0.15 0.002 0.006 b 0.26 0.41 0.010 0.016 c 0.13 0.23 0.005 0.009 d 2.90 3.10 0.114 0.122 e 0.65 bsc 0.025 bsc e 4.75 5.05 0.187 0.198 e1 2.90 3.10 0.114 0.122 l 0.41 0.71 0.016 0.028 l1 0.95 bsc 0.037 bsc s 0.525 bsc 0.021 bsc 3 3 active area required minimum light footprint bonding / wafer area examination of active area recommended light footprint pattern p1 active area a b c l c m illimeters i nches dim a 1.22 0.048 b 0.60 0.024 c 0.60 0.024 p1 2.5 0.98 note: p1 represents a possible light footprint and its dimensions are not subject to strict tolerances. only the active area of the device is required to be covered with light. this larger footprint is designed to ensure coverage of the device?s active area. m m e e c c h h a a n n i i c c a a l l s s
microsemi integrated products 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 9 copyright ? 2003 rev. 1.1b,2005-08-10 www. microsemi . com lx1971 wide ran g e visible li g ht sensor p roduction d ata s heet integrated products notes production data ? information contained in this document is proprietary to microsemi and is current as of publication date. this document may not be modified in any way without the express written consent of microsemi. product processing does not necessarily include testing of all parameters. microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. n n o o t t e e s s
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