EL7900 ® Data Sheet September 18, 2009 FN7377.8 Ambient Light Photo Detect IC Features 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. • Monolithic IC containing photodiode and amplifier 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. • Fast response time - <200µs • 1lux to 8,000lux range • Converts light intensity to current • 2.7V to 5.5V supply range • Low supply current: 1µA • Excellent output linearity of luminance • Ultra-compact and light surface mount package • Pb-free (RoHS compliant) Pinout Applications EL7900 (5 LD ODFN) TOP VIEW • Mobile phones • Notebook PCs VCC 1 GND 2 5 OUTPUT THERMAL PAD • Video cameras 4 NC EN 3 • PDAs • Digital cameras 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 L5.2x2.1 Tape and Reel EL7900ILCZ-EVALZ Evaluation Board *Please refer to TB347 for details on reel specifications. NOTE: These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate - e3 termination finish, which is 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 © Intersil Americas Inc. 2005-2008. All Rights Reserved. All other trademarks mentioned are the property of their respective owners. EL7900 Absolute Maximum Ratings (TA = +25°C) Thermal Information Supply Voltage between VSD and GND . . . . . . . . . . . . . . . . . . . .6V Maximum Continuous Output Current . . . . . . . . . . . . . . . . . . . . 6mA ESD Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV Thermal resistance (Typical, Note 1) Operating Conditions Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C θJA (°C/W) ODFN Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Maximum Die Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . +90°C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +100°C 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 for extended periods of time. Exposure to such conditions may adversely 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. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA NOTE: 1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech Brief TB379 Electrical Specifications PARAMETER VCC = 3V, TA = +25°C, unless otherwise specified. DESCRIPTION CONDITION VDD Power Supply Range ICC1 Supply Current ICC2 Supply Current When Disabled IL1 Light Current EV = 100lux IL2 Light Current EV = 10lux ILEAK Dark Current VO(MAX) Maximum Output Compliance Voltage tR Rise Time (Note 2) tF tD tS Fall Time (Note 2) Delay Time for Rising Edge (Note 2) Delay Time for Falling Edge (Note 2) VLO Maximum Voltage at EN Pin to Enable VHI Minimum Voltage at EN Pin to Disable MIN TYP 2.7 RL = 1kΩ, EV = 100lux MAX 5.5 UNIT V 68 µA EV = 0lux 1 µA EN = VHI 0.5 µA 40 62.5 85 µA 6.2 µA EV = 0lux 10 pA at 95% of nominal output current, EV = 100lux 2.7 V RL = 5kΩ, EV = 300lux 105 µs RL = 1kΩ, EV = 1000lux 64 µs RL = 5kΩ, EV = 300lux 170 µs RL = 1kΩ, EV = 1000lux 77 µs RL = 5kΩ, EV = 300lux 165 µs RL = 1kΩ, EV = 1000lux 112 µs RL = 5kΩ, EV = 300lux 65 µs RL = 1kΩ, EV = 1000lux 33 µs 0.6 1.8 V V ILO Input Current at EN Pin VEN = 0V 0.01 µA IHI Input Current at EN Pin VEN = 3V 2 µA tEN Enable Time EV = 200lux 140 µs tDIS Disable Time EV = 200lux 2 µs NOTES: 2. Switching time measurement is based on Figures 1 and 2. 3. Fluorescent light is substituted by Green LED during production 2 FN7377.8 September 18, 2009 EL7900 1ms PULSE DRIVE CH1 VCC tD tS 1V PULSE DRIVE EL7900 VS = 3V TA = +27°C VOUT RL 0.5V 80% 20% VOUT CH2 tR tF FIGURE 2. RISE/FALL TIME MEASUREMENT WAVEFORMS FIGURE 1. RISE/FALL TIME MEASUREMENT Typical Performance Curves 700 EL7900 RELATIVE RESPONSE VCC = 3V 600 FLUORESCENT LIGHT OUTPUT CURRENT (µA) RELATIVE RESPONSE (%) 100 80 60 40 EL7900 RELATIVE RESPONSE WITH IR GLASS FILTER 20 500 400 300 200 100 0 0 400 500 600 700 800 900 0 1k 200 WAVE LENGTH (nm) 400 600 800 1000 ILLUMINATION (LX) FIGURE 3. SPECTRAL RESPONSE FIGURE 4. SENSITIVITY 1000 1.20 IOUT (pA) 0 VDD = 5V -1000 -2000 VDD = 3.3V -3000 GAIN/GAIN (+25°C) VDD = 3V 1.15 FLUORESCENT LIGHT OF 50lux 1.10 1.05 1.00 0.95 0.90 0.85 -4000 -45 -35 -25 -15 -5 5 15 25 35 45 55 65 75 85 TEMPERATURE (°C) FIGURE 5. DARK CURRENT vs TEMPERATURE 3 0.80 -60 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) FIGURE 6. GAIN vs TEMPERATURE FN7377.8 September 18, 2009 EL7900 Typical Performance Curves OUTPUT COMPLIANCE VOLTAGE (VDD - VOUT) (V) 0.6 0.5 VDD = 3V TA = +27°C RADIATION PATTERN LUMINOSITY 30° ANGLE 40° 0.4 0.3 20° 10° 0° 10° 20° 30° 40° 50° 50° 60° 0.2 60° 70° 0.1 0 -200 0 200 400 600 800 1000 1200 70° 80° 80° 90° 90° 0.2 0.4 0.6 0.8 1.0 RELATIVE SENSITIVITY OUTPUT CURRENT (µA) FIGURE 7. OUTPUT COMPLIANCE VOLTAGE vs CURRENT FIGURE 8. RADIATION PATTERN 5 IOUT (mA) 4 3 FLUORESCENT LIGHT SOURCE 2 1 0 0 1k 2k 3k 4k 5k 6k 7k LUMINANCE (lux) 8k 9k 10k FIGURE 9. IOUT vs LUMINANCE Block Diagram Pin Descriptions PIN NAME 1 VCC Supply, 2.7V to 5.5V 2 GND Ground 3 EN Enable 4 NC No connect 5 Output VCC DESCRIPTION 1 3 ENABLE Current output pin 5 OUTPUT 2 GND 4 FN7377.8 September 18, 2009 EL7900 Application Information Resistor Output RLOAD Selection Product Description 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 10Ω to 10MΩ 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 10MΩ. 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 60µA. The EL7900 is housed in an ultra-compact surface mount clear plastic package. 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: 60μA I OUT = ⎛ -------------------⎞ × L INPUT ⎝ 100lux⎠ (EQ. 1) Here, IOUT is the output current in µA, 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 Equation 2: 60μA V OUT = I OUT × R LOAD = ⎛ -------------------⎞ × L INPUT × R LOAD ⎝ 100lux⎠ (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. 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 Equation 3: ( V SUP – 0.3V ) 100lux R LOAD = --------------------------------------- × ----------------------60μA L RANGE (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 4.5kΩ 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. 5 The output current must never exceed 6mA. When using load resistances less than 800Ω, 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) RLOAD (kΩ) CURRENT OUT (µA) 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 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 FN7377.8 September 18, 2009 EL7900 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 × ⎛ ---------------- – 1⎞ = 11 × R 2 ⎝ 0.25V ⎠ 3V TO 5V SUPPLY VOLTAGE Figure 12 shows how a fully manual override can be quickly added by using the EN pin. 3V TO 5V SUPPLY VOLTAGE (EQ. 4) VDO 3V DC VOLTAGE R1 110k ENABLE/ DISABLE CONTROL VDO R1 110k OUT R2 10k GND TO INVERTER BRIGHTNESS INPUT OR LED DRIVER CONTROLLER C1 25µF TO INVERTER BRIGHTNESS INPUT OR CONTROLLER EL7900 EN OUT EL7900 EN 3V PWM CONTROL GND R2 10k C1 25µF LED DRIVER FIGURE 12. AUTOMATIC DIMMING SOLUTION WITH ADJUSTABLE BIAS CONTROL AND MANUAL OVERRIDE FIGURE 10. AUTOMATIC DIMMING SOLUTION Short Circuit Current Limit 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 125µA. Thus, R2 can be calculated as shown in Equations 5 and 6: 1.25V R 2 = ⎛ ------------------⎞ = 10kΩ ⎝ 125μA⎠ (EQ. 5) and 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. Suggested PCB Footprint R 1 = 11 × R 2 = 110kΩ (EQ. 6) 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 VDO R1 110k EL7900 EN OUT GND R2 10k TO INVERTER BRIGHTNESS INPUT OR LED DRIVER CONTROLLER C1 25µF 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 0.1µF ceramic capacitor should be placed from VCC pin to GND pin. A 4.7µF tantalum capacitor should then be connected in parallel, placed close to the device. FIGURE 11. AUTOMATIC DIMMING SOLUTION WITH ADJUSTABLE BIAS CONTROL 6 FN7377.8 September 18, 2009 EL7900 FIGURE 13. EL7900 SENSOR DIAGRAM 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 7 FN7377.8 September 18, 2009 EL7900 Package Outline Drawing L5.2x2.1 5 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE Rev 1, 05/08 2.10 6 PIN #1 INDEX AREA A B 6 PIN 1 INDEX AREA 1 5 1 2.00 1.35 1.30 REF 2 0.65 0.30±0.05 4 (4X) 3 0.10 0.65 0.10 M C A B 5X 0 . 35 ± 0 . 05 TOP VIEW BOTTOM VIEW (0.65) SEE DETAIL "X" 0.10 C 0 . 7 ± 0 . 05 C ( 5X 0 . 30 ) (0.65) BASE PLANE (1.35) SEATING PLANE 0.08 C SIDE VIEW ( 5X 0 . 55 ) C 0 . 2 REF 5 (1.95) 0 . 00 MIN. 0 . 05 MAX. DETAIL "X" TYPICAL RECOMMENDED LAND PATTERN NOTES: 1. Dimensions are in millimeters. Dimensions in ( ) for Reference Only. 2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994. 3. Unless otherwise specified, tolerance : Decimal ± 0.05 4. 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. 8 The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. FN7377.8 September 18, 2009