fn7377 rev 8.00 page 1 of 8 september 18, 2009 fn7377 rev 8.00 september 18, 2009 el7900 ambient light photo detect ic datasheet the el7900 is a light-to-current optical sensor combining a photodiode and a current amplifier on a single monolithic ic. output current is directly proportionate to the light intensity on the photodiode. its sensiti vity is superior to that of a phototransistor and exhibits little variation. its spectral sensitivity matches closely to the luminous efficiency and linearity. housed in an ultra-compact su rface mount clear plastic package, this device is excellent for power saving control function in cell phones, pd as, and other handheld applications. pinout el7900 (5 ld odfn) top view features ? monolithic ic containing photodiode and amplifier ? 1lux to 8,000lux range ? converts light intensity to current ? 2.7v to 5.5v supply range ? low supply current: 1a ? fast response time - <200s ? excellent output linearity of luminance ? ultra-compact and ligh t surface mount package ? pb-free (rohs compliant) applications ? mobile phones ? notebook pcs ?pdas ? video cameras ? digital cameras 1 2 3 5 4 vcc gnd en output nc thermal pad ordering information part number (note) temp range (c) package (pb-free) pkg. dwg. # el7900ilcz -40 to +85 5 ld odfn l5.2x2.1 EL7900ILCZ-T7* -40 to +85 5 ld odfn tape and reel l5.2x2.1 el7900ilcz-evalz evaluation board *please refer to tb347 for det ails on reel specifications. note: these intersil pb-free plas tic packaged products employ special pb-free material sets ; molding compounds/die attach materials and 100% matte tin plate - e3 termination finish, w hich is rohs compliant and compatible with both snpb and pb-free soldering operations. intersil p b-free products are msl classif ied at pb-free peak reflow temperatures that meet or exceed the pb-fre e requirements of ipc/jedec j std-020.
el7900 fn7377 rev 8.00 page 2 of 8 september 18, 2009 absolute maximum ratings (t a = +25c) thermal information supply voltage between v sd and gnd . . . . . . . . . . . . . . . . . . . .6v maximum continuous output current . . . . . . . . . . . . . . . . . . . . 6ma esd voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kv operating conditions temperature range . . . . . . . . . . . . . . . . . . . . . . . . . .-40c to +85c thermal resistance (typical, note 1) ? ja (c/w) odfn package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 maximum die temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . +90c storage temperature . . . . . . . . . . . . . . . . . . . . . . . .-40c to +100c pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/pb-freereflow.asp caution: do not operate at or near the maximum ratings listed fo r extended periods of time. exposure to such conditions may adv ersely impact product reliability and result in failures not covered by warranty. important note: all parameters having min/max specifications are guaranteed. typical values are for information purposes only. u nless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: t j = t c = t a note: 1. ? ja is measured in free air with the component mounted on a high e ffective thermal conductivity t est board with direct attach f eatures. see tech brief tb379 electrical specifications v cc = 3v, t a = +25c, unless otherwise specified. parameter description condition min typ max unit v dd power supply range 2.7 5.5 v i cc1 supply current r l = 1k ? , ev = 100lux 68 a ev = 0lux 1 a i cc2 supply current when disabled en = v hi 0.5 a i l1 light current ev = 100lux 40 62.5 85 a i l2 light current ev = 10lux 6.2 a i leak dark current ev = 0lux 10 pa v o(max) maximum output compliance voltage at 95% of nominal output curre nt, ev = 100lux 2.7 v t r rise time (note 2) r l = 5k ? , ev = 300lux 105 s r l = 1k ? , ev = 1000lux 64 s t f fall time (note 2) r l = 5k ? , ev = 300lux 170 s r l = 1k ? , ev = 1000lux 77 s t d delay time for rising edge (note 2) r l = 5k ? , ev = 300lux 165 s r l = 1k ? , ev = 1000lux 112 s t s delay time for falling edge (note 2) r l = 5k ? , ev = 300lux 65 s r l = 1k ? , ev = 1000lux 33 s v lo maximum voltage at en pin to enable 0.6 v v hi minimum voltage at en pin to disable 1.8 v i lo input current at en pin v en = 0v 0.01 a i hi input current at en pin v en = 3v 2 a t en enable time ev = 200lux 140 s t dis disable time ev = 200lux 2 s notes: 2. switching time measurement is based on figures 1 and 2. 3. fluorescent light is substitu ted by green led during producti on
el7900 fn7377 rev 8.00 page 3 of 8 september 18, 2009 el7900 pulse drive v cc r l v out figure 1. rise/fall time measurement ch1 ch2 pulse drive v out t d t r 80% 20% t s t f 1ms 1v 0.5v v s = 3v t a = +27c figure 2. rise/fall tim e measurement waveforms typical performance curves figure 3. spectral respons e figure 4. sensitivity figure 5. dark current vs temperature figure 6. gain vs temperatu re 0 20 40 60 80 100 400 500 600 700 800 900 1k wave length (nm) relative response (%) el7900 relative response el7900 relative response with ir glass filter illumination (l x ) output current (a) 700 600 400 200 0 500 300 100 0 200 400 600 800 1000 v cc = 3v fluorescent light -4000 -3000 -2000 -1000 0 1000 -45-35-25-15-5 5 1525354555657585 i out (pa) temperature (c) v dd = 5v v dd = 3.3v temperature (c) gain/gain (+25c) 1.20 1.15 0.95 0.80 1.05 0.85 -60 -40 0 40 80 100 -20 20 60 1.10 0.90 1.00 v dd = 3v fluorescent light of 50lux
el7900 fn7377 rev 8.00 page 4 of 8 september 18, 2009 block diagram figure 7. output compliance voltage vs current figure 8. radiation pattern figure 9. i out vs luminance typical performance curves output current (a) output compliance voltage (v dd - v out ) (v) 0.6 0.5 0.2 0 0.3 0.1 -200 0 400 800 1000 1200 200 600 v dd = 3v t a = +27c 0.4 radiation pattern luminosity angle relative sensitivity 90 80 70 60 50 40 30 20 10 0 90 80 70 60 50 40 30 20 10 0.20.4 0.60.81.0 0 1 2 3 4 5 0 1k2k3k4k5k6k7k8k9k10k luminance (lux) i out (ma) fluorescent light source pin name description 1 vcc supply, 2.7v to 5.5v 2 gnd ground 3en enable 4 nc no connect 5 output current output pin enable output gnd vcc 1 2 5 3
el7900 fn7377 rev 8.00 page 5 of 8 september 18, 2009 application information product description the el7900 is a light-to-curr ent optical sensor combining photodiodes and current amplifier s on a single monolithic ic. the photodiodes are temperat ure-compensated and their spectrum resembles the human eye response. the output current is directly proportional to the intensity of light fall ing on the photodiodes. for 100lux of input fluorescent light, the el7900 has an output current of 60a. the el7900 is housed in an ultra-compact surface mount clear plastic package. light-to-current and voltage conversion the el7900 has a responsiveness th at is directly proportional to the intensity of light int ercepted by the photodiodes. although the conversion rate varies depending on the light sources (fluorescent light, incandescent light or direct sunlight), in general for a fluor escent light, the light-to-cur rent conversion is: here, i out is the output current in a, and l input is the input light in lux. for some applications, a load re sistor is added between the output and the ground as shown in figure 1. the output voltage can be expressed in equation 2: here, v out is the output voltage and r load is the value of the load resistor added. the comp liance of the e l7900's output circuit may result in premature s aturation of the output curren t and voltage when an excessively large r load is used. the output compliance voltage is 3 00mv below the supply voltage as listed in v o(max) of the electrical spec ifications table on page 2. in order to have the linear rela tionship between the input ligh t and the output current and voltage, a proper resistor value (i. e., gain) should be picked for a sp ecific input light range. the resistor value can be pick ed according to equation 3: here, v sup is the supply voltage, and l range is the specific input light range for an application. for example, an indoor li ght ranges typically from 0lux to 1,000lux. a resistor value of 4.5 k ? for 3v supply voltage can be us ed. for a small light range, a large resistor value should be used to achieve better sensitivity; for a l arge light range, a small resistor value sh ould be used to prevent non-linear output current and voltage. resistor output r load selection the resistor output, r load , determines the vo ltage transfer function of the device. the device converts light into current then r load converts the output curre nt to an output voltage. r load can range from 10 ? to 10m ? depending on the input lux levels. the table below lists r load values to maximize output swing for typical lux ra nge levels. a careful balance of dynamic swing and fast respons e has to be considered when choosing r load . for faster response, choose a smaller value r load to shunt stray capacitances that may slow down response time. for maximum dynamic range or swing, choose a higher value r load . although finite, the output impedance of the device is considerably large . hence, the light-to-current conversion deviation becaus e of resistor loading is infinitesimal. the recommended maximum r load is 10m ? . the output current must never e xceed 6ma. when using load resistances less than 800 ? , care must be taken when lux go as high as 10,000lux because the ou tput current rises above 6ma before reaching the devices output compliance. the output compliance of the device is 300mv below the supply. the output current stops ramping wh en the output voltage reaches voltage compliance. application examples the following examples present fr om fully automatic to fully manual override implementations. these guidelines are applicable to a wide variet y of potential light control applications. the el7900 c an be used to c ontrol the brightness input of ccfl inverter s. likewise, it can interface well with led driver s. in each specific application, it is important to recognize the targe t environment and its ambient light conditions. the mechanical mounting of the sensor, light aperture hole size and use of a light pipe or bezel are critica l in determining the response of the el7900 for a given exposure of light. the example in figure 10 show s a fully automatic dimming solution with no user interaction. choose r 1 and r 2 values for any desired minimum brig htness and slope. choose c 1 to adjust response time and to filte r 50/60hz room lighting. for example, suppose you wish to gen erate an output voltage from 0.25v to 1.25v to drive the inpu t of an led driver controller. the 0.25v represents the minimum led brightness and 1.25v i out 60 ? a 100lux ------------------ - ?? ?? l input ? = (eq. 1) v out i out r load ? 60 ? a 100lux ------------------ - ?? ?? l input r load ? ? == (eq. 2) r load v sup 0.3v C ?? 60 ? a -------------------------------------- - 100lux l range ----------------------- ? = (eq. 3) table 1. v dd = 5v, maximum output voltage = 4.7v illumination range (lux) rload (k ? ) current out (a) 0 to 10 783 0 to 6 0 to 200 39.2 0 to 120 0 to 500 15.7 0 to 300 0 to 1,000 7.8 0 to 600 0 to 10,000 0.78 0 to 6,000
el7900 fn7377 rev 8.00 page 6 of 8 september 18, 2009 represents the maximum. the fir st step would be to determine the ratio of r 1 and r 2 : next, the value of r 2 can be calculated based on the maximum output current comi ng from the el7900 under the application's maximum light exp osure. suppose the current has been determined to b e about 125a. thus, r 2 can be calculated as shown in equations 5 and 6: and in figure 11, 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 persona l preference over a limit ran ge via the 3v pwm control. figure 12 shows how a fully m anual override can be quickly added by using the en pin. short circuit current limit the el7900 does not limit the output short circuit current. if the output is directly shorted to the ground continuously, the outp ut current could easily increase fo r a strong input light such tha t the device may be damaged. maximum reliability is maintained if the output c ontinuous current never e xceeds 6ma by adding a load resistor at t he output. this limit is set by the design of the internal metal interconnects. suggested pcb footprint footprint pads should be a no minal 1-to-1 correspondence with package pads. the large, ex posed central die-mounting paddle in the center of the package requires neither thermal nor electrical connections t o pcb, and such connections should be avoided. power supply bypassing and printed circuit board layout the el7900 is relatively insens itive to the printed circuit boa rd layout due to its low speed ope ration. nevertheless, good printed circuit board layout is necessary f or optimum performance. ground plane construction is highly recommended, lead length should be as short as possible and the power supply pins must be well bypassed to reduce the risk of oscillation. for normal sing le supply operation, where the gnd pin is connected to ground , a 0.1f ceramic capacitor should be placed from vcc pin t o gnd pin. a 4.7f tantalum capacitor should then be connected in parallel, placed close to the device. r 1 r 2 3.0v 0.25v --------------- - 1 C ?? ?? ? 11 r 2 ? == (eq. 4) 3v to 5v supply voltage 3v dc voltage el7900 out en gnd vdo to inverter brightness controller c 1 r 2 r 1 figure 10. automatic dimming solution 10k 25f 110k input or led driver r 2 1.25v 125 ? a ----------------- - ?? ?? 10k ? == (eq. 5) r 1 11 r 2 ? 110k ? == (eq. 6) 3v to 5v supply voltage 3v pwm control el7900 out en gnd vdo figure 11. automatic dimming solution with adjustable bias control c 1 r 2 r 1 10k 25f 110k to inverter brightness controller input or led driver 3v to 5v supply voltage 3v pwm control el7900 out en gnd vdo figure 12. automatic dimming solution with adjustable bias control and manual override enable/ control disable c 1 r 2 r 1 10k 25f 110k to inverter controller brightness led driver input or
fn7377 rev 8.00 page 7 of 8 september 18, 2009 el7900 intersil products are manufactured, assembled and tested utilizing iso9001 quality systems as noted in the quality certifications found at www.intersil.com/en/suppor t/qualandreliability.html intersil products are sold by description on ly. intersil may modify the circuit design an d/or specifications of products at any time without notice, provided that such modification does not, in intersil's sole judgment, affect the form, fit or function of the product. accordingly, the reader is cautioned to verify that datasheets are current before placing orders. information fu rnished by intersil is believed to be accu rate and reliable. however, no responsib ility is assumed by intersil or its subsidiaries for its use; nor for any infrin gements of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of intersil or its subsidiaries. for information regarding intersil corporation and its products, see www.intersil.com for additional products, see www.intersil.com/en/products.html ? copyright intersil americas ll c 2005-2008. all rights reserved. all trademarks and registered trademarks are the property of their respective owners. figure 13. el7900 sensor diagram
el7900 fn7377 rev 8.00 page 8 of 8 september 18, 2009 package outline drawing l5.2x2.1 5 lead optical dual flat no-lead plastic package rev 1, 05/08 located within the zone indicated. the pin #1 identifier may be unless otherwise specified, tolerance : decimal 0.05 tiebar shown (if present) is a non-functional feature. the configuration of the pin #1 identifier is optional, but mus t be between 0.15mm and 0.30mm from the terminal tip. dimension b applies to the metallized terminal and is measured dimensions in ( ) for reference only. dimensioning and tolerancing conform to amse y14.5m-1994. 6. either a mold or mark feature. 3. 5. 4. 2. dimensions are in millimeters. 1. notes: bottom view detail "x" side view typical recommended land pattern top view 1 2 3 5 4 (4x) 0.10 index area pin 1 a 2.10 b 2.00 pin #1 index area 5x 0 . 35 0 . 05 b 0.10 ma c c seating plane base plane 0.08 0.10 see detail "x" c c 0 . 00 min. 0 . 05 max. 0 . 2 ref c 5 1 ( 5x 0 . 30 ) ( 5x 0 . 55 ) 6 6 (0.65) (1.95) (0.65) (1.35) 0.65 1.35 1.30 ref 0.65 0.300.05 0 . 7 0 . 05
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