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| (R) EL7900 Data Sheet February 6, 2007 FN7377.5 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 excellent for power saving control function in cell phones, PDAs, and other handheld applications. Features * Monolithic IC containing photodiode and amplifier * 1lux to 8,000lux range * Converts light intensity to current * 2.5V to 5.5V supply range * Low supply current: 1A * Fast response time - <200s * Excellent output linearity of luminance * Ultra-compact and light surface mount package * Pb-free plus anneal available (RoHS compliant) Pinout EL7900 (5 LD ODFN) TOP VIEW Applications * Mobile phones * Notebook PCs * PDAs VCC OUTPUT * Video cameras * Digital cameras GND Ordering Information EN NC PART NUMBER (Note) EL7900ILCZ EL7900ILCZ-T7 TAPE & REEL 7" PACKAGE (Pb-free) 5 Ld ODFN 5 Ld ODFN PKG. DWG. # L5.2x2.1 L5.2x2.1 NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. 1 CAUTION: These devices are sensitive to electrostatic 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 (c) Intersil Americas Inc. 2005-2007. All Rights Reserved. All other trademarks mentioned are the property of their respective owners. EL7900 Absolute Maximum Ratings (TA = +25C) Supply Voltage between VSD 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: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA Electrical Specifications PARAMETER ICC1 Supply Current VCC = 3V, TA = +25C, fluorescent light, unless otherwise specified. CONDITION RL = 1k, EV = 100lux EV = 0lux MIN TYP 62 1 1.2 39 60.5 6.2 10 2.7 105 64 170 77 165 112 65 33 0.6 1.8 VEN = 0V VEN = 3V EV = 200lux EV = 200lux 0.01 2 140 2 85 200 225 125 82 MAX UNIT A A A A A pA V s s s s s s s s V V A A s s DESCRIPTION ICC2 IL1 IL2 ILEAK VO(MAX) tR Supply Current When Disabled Light Current Light Current Dark Current Maximum Output Compliance Voltage Rise Time (Note 1) EN = VHI EV = 100lux EV = 10lux EV = 0lux at 95% of nominal output current, EV = 100lux RL = 5k, EV = 300lux RL = 1k, EV = 1000lux tF Fall Time (Note 1) RL = 5k, EV = 300lux RL = 1k, EV = 1000lux tD Delay Time for Rising Edge (Note 1) RL = 5k, EV = 300lux RL = 1k, EV = 1000lux tS Delay Time for Falling Edge (Note 1) RL = 5k, EV = 300lux RL = 1k, EV = 1000lux VLO VHI ILO IHI tEN tDIS NOTE: Maximum Voltage at EN Pin to Enable Minimum Voltage at EN Pin to Disable Input Current at EN Pin Input Current at EN Pin Enable Time Disable Time 1. Switching time measurement is based on Figures 1 and 2. PULSE DRIVE CH1 VCC 1V PULSE DRIVE VS = 3V TA = +27C 0.5V VOUT tR 80% 20% tF tD tS 1ms EL7900 RL VOUT CH2 FIGURE 1. RISE/FALL TIME MEASUREMENT FIGURE 2. RISE/FALL TIME MEASUREMENT WAVEFORMS 2 FN7377.5 February 6, 2007 EL7900 Typical Performance Curves 700 100 RELATIVE RESPONSE (%) 80 60 40 20 0 400 500 600 700 800 900 1k WAVE LENGTH (nm) EL7900 RELATIVE RESPONSE WITH IR GLASS FILTER EL7900 RELATIVE RESPONSE OUTPUT CURRENT (A) VCC = 3V 600 FLUORESCENT LIGHT 500 400 300 200 100 0 0 200 400 600 800 1000 ILLUMINATION (LX) FIGURE 3. SPECTRAL RESPONSE FIGURE 4. SENSITIVITY 1000 1.20 VDD = 3V 1.15 FLUORESCENT LIGHT OF 50lux 0 GAIN/GAIN (+25C) VDD = 5V 1.10 1.05 1.00 0.95 0.90 0.85 IOUT (pA) -1000 -2000 VDD = 3.3V -3000 -4000 -45 -35 -25 -15 -5 5 15 25 35 45 55 65 75 85 TEMPERATURE (C) 0.80 -60 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) FIGURE 5. DARK CURRENT vs TEMPERATURE FIGURE 6. GAIN vs TEMPERATURE 0.6 OUTPUT COMPLIANCE VOLTAGE (VDD - VOUT) (V) 0.5 0.4 0.3 0.2 0.1 VDD = 3V TA = +27C LUMINOSITY 30 ANGLE 40 50 60 70 80 90 0 200 400 600 800 1000 1200 OUTPUT CURRENT (A) RADIATION PATTERN 20 10 0 10 20 30 40 50 60 70 80 90 0.2 0.4 0.6 0.8 1.0 RELATIVE SENSITIVITY 0 -200 FIGURE 7. OUTPUT COMPLIANCE VOLTAGE vs CURRENT FIGURE 8. RADIATION PATTERN 3 FN7377.5 February 6, 2007 EL7900 Typical Performance Curves 5 4 3 2 1 0 FLUORESCENT LIGHT SOURCE IOUT (mA) 0 1k 2k 3k 4k 5k 6k 7k LUMINANCE (lux) 8k 9k 10k FIGURE 9. IOUT vs LUMINANCE Pin Descriptions PIN 1 2 3 4 5 NAME VCC GND EN NC Output DESCRIPTION Supply, 2.5V to 5.5V Ground Enable No connect Current output pin Application Information Product Description The EL7900 is a light-to-current optical sensor combining photodiodes and current amplifiers on a single monolithic IC. The photodiodes are temperature-compensated and their spectrum resembles the human eye response. The output current is directly proportional to the intensity of light falling 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. Block Diagram VCC 1 Light-to-Current and Voltage Conversion The EL7900 has a responsiveness 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 for a fluorescent light, the light-tocurrent conversion is: 5 OUTPUT 3 ENABLE 60A I OUT = ------------------ x L INPUT 100lux (EQ. 1) Here, IOUT is the output current in A, and LINPUT 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: 60A V OUT = I OUT x R LOAD = ------------------ x L INPUT x R LOAD 100lux 2 GND (EQ. 2) Here, VOUT is the output voltage and RLOAD 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 RLOAD is used. The output compliance voltage is 300mV below the supply voltage as listed in VO(MAX) of the Electrical Specifications table on page 2. 4 FN7377.5 February 6, 2007 EL7900 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: ( V SUP - 0.3V ) 100lux R LOAD = -------------------------------------- x ----------------------60A L RANGE 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 R1 and R2 values for any desired minimum brightness and slope. Choose C1 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 R1 and R2: 3.0V R 1 = R 2 x --------------- - 1 = 11 x R 2 0.25V (EQ. 4) (EQ. 3) Here, VSUP is the supply voltage, and LRANGE is the specific input light range for an application. For example, an indoor light ranges typically from 0lux to 1,000lux. 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 RLOAD Selection The resistor output, RLOAD, determines the voltage transfer function of the device. The device converts light into current then RLOAD converts the output current to an output voltage. RLOAD can range from 10 to 10M depending on the input lux levels. The table below lists RLOAD 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 RLOAD. For faster response, choose a smaller value RLOAD to shunt stray capacitances that may slow down response time. For maximum dynamic range or swing, choose a higher value RLOAD. Although finite, the output impedance of the device is considerably large. Hence, the light-to-current conversion deviation because of resistor loading is infinitesimal. The recommended maximum RLOAD 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 10,000lux because the output current rises above 6mA before reaching the device's output compliance. The output compliance of the device is 300mV below the supply. The output current stops ramping when the output voltage reaches voltage compliance. TABLE 1. VDD = 5V, MAXIMUM OUTPUT VOLTAGE = 4.7V ILLUMINATION RANGE (lux) 0 to 10 0 to 200 0 to 500 0 to 1,000 0 to 10,000 RLOAD (k) 783 39.2 15.7 7.8 0.78 CURRENT OUT (A) 0 to 6 0 to 120 0 to 300 0 to 600 0 to 6,000 3V TO 5V SUPPLY VOLTAGE 3V DC VOLTAGE VDO R2 110k EL7900 EN OUT R1 10k TO INVERTER BRIGHTNESS INPUT OR LED DRIVER CONTROLLER C1 25F GND FIGURE 10. AUTOMATIC DIMMING SOLUTION Next, the value of R2 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, R2 can be calculated approximately as follows: 1.25V R 2 = ----------------- = 10k 125A (EQ. 5) and R 1 = 11 x R 2 = 110k (EQ. 6) 5 FN7377.5 February 6, 2007 EL7900 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. 3V TO 5V SUPPLY VOLTAGE 3V PWM CONTROL 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 output current could easily increase for a strong input light such that the device may be damaged. Maximum reliability is maintained if the output continuous current never exceeds 6mA by adding a load resistor at the output. This limit is set by the design of the internal metal interconnects. VDO R2 110k 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. EL7900 EN OUT R1 10k TO INVERTER BRIGHTNESS INPUT OR LED DRIVER CONTROLLER C1 25F GND Power Supply Bypassing and Printed Circuit Board Layout FIGURE 11. AUTOMATIC DIMMING SOLUTION WITH ADJUSTABLE BIAS CONTROL Figure 12 shows how a fully manual override can be quickly added by using the EN pin. 3V TO 5V SUPPLY VOLTAGE 3V PWM CONTROL VDO R2 110k ENABLE/ DISABLE CONTROL 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. EL7900 EN OUT R1 10k TO INVERTER BRIGHTNESS INPUT OR CONTROLLER C1 25F GND LED DRIVER FIGURE 12. AUTOMATIC DIMMING SOLUTION WITH ADJUSTABLE BIAS CONTROL AND MANUAL OVERRIDE All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation's quality certifications can be viewed at www.intersil.com/design/quality Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished 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 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 6 FN7377.5 February 6, 2007 EL7900 Package Outline Drawing L5.2x2.1 5 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE Rev 0, 01/07 2.10 A 6 PIN #1 INDEX AREA B 6 PIN 1 INDEX AREA 1 5 1 2.00 1.35 2 0.65 0.300.05 1.30 REF 4 3 0.65 0.10 M C A B (4X) 0.10 TOP VIEW 5X 0 . 35 0 . 05 BOTTOM VIEW (0.65) SEE DETAIL "X" 0.10 C C (0.65) (1.35) ( 5X 0 . 30 ) SIDE VIEW BASE PLANE SEATING PLANE 0.08 C ( 5X 0 . 55 ) (1.95) C 0 . 2 REF 5 0 . 00 MIN. 0 . 05 MAX. TYPICAL RECOMMENDED LAND PATTERN DETAIL "X" NOTES: 1. Dimensions are in millimeters. Dimensions in ( ) for Reference Only. 2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994. 3. 4. Unless otherwise specified, tolerance : Decimal 0.05 Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 5. Tiebar shown (if present) is a non-functional feature. 6. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 indentifier may be either a mold or mark feature. 7 FN7377.5 February 6, 2007 |
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