1 ? fn7377.6 caution: these devices are sensitive to electrosta tic discharge; follow proper ic handling procedures. 1-888-intersil or 1-888-468-3774 | intersil (and design) is a registered trademark of intersil americas inc. copyright ? intersil americas inc. 2005-2007. all rights reserved. all other trademarks mentioned are the property of their respective owners. EL7900 ambient light photo detect ic 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 sensitivity 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 surface mount clear plastic package, this device is excelle nt for power saving control function in cell phones, pdas, and other handheld applications. pinout EL7900 (5 ld odfn) top view features ? monolithic ic containing photodiode and amplifier ? 1 lux to 8,000 lux range ? converts light intensity to current ? 2.5v to 5.5v supply range ? low supply current: 1a ? fast response time: <200s ? excellent output line arity of luminance ? ultra-compact and light surface mount package ? pb-free plus anneal available (rohs compliant) applications ? mobile phones ? notebook pcs ?pdas ? video cameras ? digital cameras vcc gnd en output nc ordering information part number (note) tape & reel package (pb-free) pkg. dwg. # EL7900ilcz - 5 ld odfn l5.2x2.1 EL7900ilcz-t7 7? 5 ld odfn l5.2x2.1 note: intersil pb-free products em ploy special pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which ar e rohs compliant and compatible with both snpb and pb-free soldering operations. intersil pb-free products are msl classified at pb-f ree peak reflow temperatures that meet or exceed the pb-free requirements of ipc/jedec j std-020. data sheet august 1, 2007
2 fn7377.6 august 1, 2007 absolute maxi mum ratings (t a = +25c) supply voltage between v sd and gnd . . . . . . . . . . . . . . . . . . . .6v maximum continuous output current . . . . . . . . . . . . . . . . . . . . 6ma operating temperature . . . . . . . . . . . . . . . . . . . . . . .-40c to +85c esd voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kv maximum die temperature . . . . . . . . . . . . . . . . . . . . . . . . . . +125c storage temperature . . . . . . . . . . . . . . . . . . . . . . . .-45c to +100c 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 electrical specifications v cc = 3v, t a = +25c, fluorescent light, unless otherwise specified. parameter description condition min (note 2) typ max (note 2) unit i cc1 supply current r l = 1k , ev = 100 lux 62 a ev = 0 lux 1 a i cc2 supply current when disabled en = v hi 1.2 a i l1 light current ev = 100 lux 39 60.5 82 a i l2 light current ev = 10 lux 6.2 a i leak dark current ev = 0 lux 10 pa v o(max) maximum output compliance voltage at 95% of nominal output current, ev = 100 lux 2.7 v t r rise time (note 1) r l = 5k , ev = 300 lux 105 125 s r l = 1k , ev = 1000 lux 64 s t f fall time (note 1) r l = 5k , ev = 300 lux 170 225 s r l = 1k , ev = 1000 lux 77 s t d delay time for rising edge (note 1) r l = 5k , ev = 300 lux 165 200 s r l = 1k , ev = 1000 lux 112 s t s delay time for falling edge (note 1) r l = 5k , ev = 300 lux 65 85 s r l = 1k , ev = 1000 lux 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 = 200 lux 140 s t dis disable time ev = 200 lux 2 s notes: 1. switching time measurement is based on figures 1 and 2. 2. parts are 100% tested at +25c. over-temperature limits established by characterization and are not production tested. 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 time measurement waveforms EL7900
3 fn7377.6 august 1, 2007 typical performance curves figure 3. spectral response figure 4. sensitivity figure 5. dark current vs temperature figure 6. gain vs temperature figure 7. output compliance voltage vs current figure 8. radiation pattern 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 50 lux 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 90o 80o 70o 60o 50o 40o 30o 20o 10o 0o 90o 80o 70o 60o 50o 40o 30o 20o 10o 0.20.4 0.60.81.0 EL7900
4 fn7377.6 august 1, 2007 block diagram application information product description the EL7900 is a light-to-curr ent optical sensor combining photodiodes and current amplifiers on a single monolithic ic. the photodiodes are temperature-compensated and their spectrum resembles the huma n eye response. the output current is directly proportional to the intensity of light falling on the photodiodes. for 100 lux 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 responsiv eness that is directly proportional to the intensity of light intercepted by the photodiodes. although the conversion rate varies depending on the light sources (fluorescent light, incandescent light or direct sunlight), in general fo r a fluorescent light, the light-to- current 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 resistor is added between the output and the ground as shown in figure 1. the output voltage can be expressed in the following equation: here, v out is the output voltage and r load is the value of the load resistor added. the compliance of the EL7900's output circuit may result in premature saturation of the output current and voltage when an excessively large r load is used. the output compliance voltage is 300mv below the supply voltage as listed in v o(max) of the electrical specifications table on page 2. figure 9. i out vs luminance typical performance curves 0 1 2 3 4 5 0 1k2k3k4k5k6k7k8k9k10k luminance (lux) i out (ma) fluorescent light source pin descriptions pin name description 1 vcc supply, 2.5v 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 i out 60 a 100lux ------------------ - ?? ?? l input = (eq. 1) v out i out r load 60 a 100 lux -------------------- - ?? ?? l input r load == (eq. 2) EL7900
5 fn7377.6 august 1, 2007 in order to have the linear relationship between the input light and the output current and voltage, a proper resistor value (i.e., gain) should be picked for a specific input light range. the resistor value can be picked according to the following equation: here, v sup is the supply voltage, and l range is the specific input light range for an application. for example, an indoor light ranges typically from 0 lux to 1,000 lux. a resistor value of 4.5k for 3v supply voltage can be used. for a small light range, a large resistor value should be used to achieve better sensitivity; for a large light range, a small resistor value should be used to prevent non-linear output current and voltage. resistor output r load selection the resistor output, r load , determines the voltage transfer function of the device. the device converts light into current then r load converts the output current 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 range levels. a careful balance of dynamic swing and fast response 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 co nversion deviation because of resistor loading is infinitesimal. the recommended maximum r load is 10m . the output current must never exceed 6ma. when using load resistances less than 800 , care must be taken when lux go as high as 10,000 lux bec ause the output current rises above 6ma before reaching th e device?s output compliance. the output compliance of the device is 300mv below the supply. the output current stop s ramping when the output voltage reaches voltage compliance. application examples the following examples present from fully automatic to fully manual override implementations. these guidelines are applicable to a wide variety of potential light control applications. the EL7900 can be used to control the brightness input of ccfl inverters. likewise, it can interface well with led drivers. in each specific application, it is important to recognize the target 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 critical in determining the response of the EL7900 for a given exposure of light. the example in figure 10 shows a fully automatic dimming solution with no user interaction. choose r 1 and r 2 values for any desired minimum brightness and slope. choose c 1 to adjust response time and to filter 50/60hz room lighting. for example, suppose 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 represents the maximum. the first 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 coming from the EL7900 under the application's maximum light exposure. suppose the current has been determined to be about 125a. thus, r 2 can be calculated approximately as follows: and 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 r load v sup 0.3v ? () 60 a -------------------------------------- - 100 lux l range ----------------------- = (eq. 3) r 1 r 2 3.0v 0.25v --------------- - 1 ? ?? ?? 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) EL7900
6 all intersil u.s. products are manufactured, asse mbled and tested utilizing iso9000 quality systems. intersil corporation?s quality certifications ca n be viewed at www.intersil.com/design/quality intersil products are sold by description only. intersil corpor ation reserves the right to make changes in circuit design, soft ware and/or specifications at any time without notice. accordingly, the reader is cautioned to verify that data sheets are current before placing orders. information furnishe d by intersil is believed to be accurate and reliable. however, no responsibility is assumed by intersil or its subsidiaries for its use; nor for any infringements of paten ts 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 subsidiari es. for information regarding intersil corporation and its products, see www.intersil.com fn7377.6 august 1, 2007 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 personal preference over a limit range via the 3v pwm control. figure 12 shows how a fully manual override can be quickly added by using the en pin. short circuit current limit the EL7900 does not limit the out put short circuit current. if the output is directly shorted to the ground continuously, the output current could easily increase for a strong input light such that the device may be damaged. maximum reliability is maintained if the output cont inuous current never exceeds 6ma by adding a load resistor at the output. this limit is set by the design of the internal metal interconnects. suggested pcb footprint footprint pads should be a nominal 1-to-1 correspondence with package pads. the large, exposed central die-mounting paddle in the center of the package requires neither thermal nor electrical connections to pcb, and such connections should be avoided. power supply bypassing and printed circuit board layout the EL7900 is relatively insensitive to the printed circuit board layout due to its low speed operation. nevertheless, good printed circuit board layout is necessary for 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 single supply operation, where the gnd pin is connected to ground, a 0.1f ceramic capacitor should be placed from vcc pin to gnd pin. a 4.7f tantalum capacitor should then be connected in parallel, placed close to the device. 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 EL7900
7 fn7377.6 august 1, 2007 EL7900 package outline drawing l5.2x2.1 5 lead optical dual flat no-lead plastic package rev 0, 01/07 located within the zone indicated. the pin #1 indentifier 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 must 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
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