LX1971

LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET DESCRIPTION KEY FEATURES W WW . Microsemi . C OM 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 5KΩ to 50KΩ 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 8pin MSOP package. 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 IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com Protected By U.S. Patents: 6,787,757; Patents Pending PRODUCT HIGHLIGHT VDD 4.7uF VDD 25K SNK 0.60V Typ SNK LX1971 SRC 4.7uF 25K VOUT 0.45V Typ SRC GND Ambient Light LX1971 LX1971 PACKAGE ORDER INFO Plastic MSOP DU 8-Pin TA (°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) Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET ABSOLUTE MAXIMUM RATINGS VDD ................................................................................................................. -0.3 to 6 VDC SNK/SRC (Output Compliance Voltage)........................................... -0.3 to VDD + 0.3VDC SNK/SRC (Maximum Output Current)................................................... Internally Limited Operating Temperature Range ........................................................................ -40 to +85°C Storage Temperature Range.......................................................................... -40 to +100°C Solder Reflow Peak Temperature (Soldering 10 seconds) ......................................... 240°C Notes: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of specified terminal. Solder reflow to follow: IPC/JEDEC J-STD-020B 7/02 Pb-SN Small Body Profile VDD NC NC SRC PACKAGE PIN OUT 1 2 3 4 8 7 6 5 VSS NC NC SNK W WW . Microsemi . C OM DU PACKAGE (Top View) 8 1 1971 xxxx 7 2 3 4 THERMAL DATA 6 5 DU Plastic MSOP 8-Pin 206°C/W 39°C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA THERMAL RESISTANCE-JUNCTION TO CASE, θJC DU PACKAGE (Bottom View) xxxx = Denotes Date Code / Lot Information RoHS / Pb-free Gold Lead Finish MSL 2 / 260°C / 1 Year FUNCTIONAL PIN DESCRIPTION NAME VDD VSS SNK SRC Input Supply Voltage Ground Reference for Power and Signal Output Output Current Sink Output Current Source PACKAGE PHOTO DESCRIPTION SIMPLIFIED BLOCK DIAGRAM V DD PACKAGE DATA PACKAGE DATA SNK SRC V SS Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET RECOMMENDED OPERATING CONDITIONS Parameter Supply Voltage (VDD ) SNK Compliance Voltage Range SRC Compliance Voltage Range SNK/SRC Output Resistor Range ¹Outputs are functional down to VDD=2.7V W WW . Microsemi . C OM Min 3¹ VSS +0.6 VSS 5 LX1971 Typ Max 5.5 VDD VDD - 0.75 100 Units V V V KΩ ELECTRICAL CHARACTERISTICS Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C ≤ TA ≤ 85°C, VDD = 3V to 5.5V, RLOAD= 25Kohms, Direct Light Input² of 584µW/cm2 except where otherwise noted. Performance between -40°C and 0°C and between 70°C and 85°C are assured by design and characterization. Parameter Supply Voltage Range Input Supply Current Symbol VDD IDD ISRC ISRC Test Conditions Min 3 LX1971 Typ Max 5.5 Units VDC µA µA VDD = 3.0V, ISRC = 62µA, ISNK = open VDD = 3.0V, Direct Light Input of 2 584µW/cm @ 25°C VDD = 3.0V, Direct Light Input of 2 584µW/cm VDD = 3.0V, Direct Light Input of 2 584µW/cm VDD = 3.0V, Direct Light Input of 2 292µW/cm VDD = 3.0V, Direct Light Input of 2 9.34µW/cm VDD = 3.0V VDD = 3.0V, @ 95% of nominal output current VDD = 3.0V, @ 95% of nominal output current VDD = 3V, No Light, 25°C VDD = 3V, No Light, -40°C to 70°C VDD = 3V, No Light, 85°C VDD = 5.5V, No Light, 25°C 350 55 52 -70 34 5.5 590 61 61 -61 41 7 2 VSS +0.45 VDD – 0.6 150 450 550 320 520 ±60 750 67 70 -52 48 8.5 6 VSS +0.6 VDD – 0.7 400 1000 1150 Output Current ISNK ISRC ISRC µA µA µA % V V nA nA nA nA Output SNK/SRC Current Matching SNK Minimum Compliance Voltage SRC Maximum Compliance Voltage SNK/SRC Output Dark Current SNK/SRC Output Dark Current SNK/SRC Output Dark Current SNK/SRC Output Dark Current Wavelength of Peak Sensitivity Half Reception Angle Supply Voltage Coefficient of Output Current Resolution Limit Due To Random Noise Sensitivity Change @ 910nm Radiant Sensitive Area IMATCH SNKVMIN SRCVMAX IDARK3.0V IDARK3.0V IDARK3.0V IDARK5.5V λPS θ½ PSRR IMIN ISRC∆ IR A E ELECTRICALS nm deg 3.5 %/V nW/cm 10 2 VDD = 3V to 5.5V Minimum usable resolution Current responsivity change with 2 additional direct light input of 584µW/cm at 910nm, TA = 25°C, VDD = 3V Photodiode Area -10 2.9 146 0 .369 2 % of peak mm 2 ²The input irradiance is supplied from a white light-emitting diode (LED) optical source adjusted to impose 584µW/cm at 555nm on the sensor’s surface. Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET APPLICATION INFORMATION W WW . Microsemi . C OM SRC Current (µA) 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. LX1971 Calculated SRC Full Range Response 250 200 150 100 50 0 0 5000 10000 15000 20000 25000 Incandescent Light (lux) I OUT = 20000 lux ( L × .808 + 1.1µA for L < 2500 lux ) 2500 Lux Formula I OUT = (L × .0083µA) + 23µA for 2500 lux < L < 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 provide 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 of 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 Low Level Response 50 SRC Current (µA) 40 30 20 10 0 0 500 1000 1500 2000 2500 Incandescent Light (lux) 2500 Lux Formula Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET APPLICATION EXAMPLES W WW . Microsemi . C OM 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 for 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 sink and source current of the LX1971 for the target environment and its ambient light conditions. The mechanical mounting 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. 3.3V or 5V VDD VSS SNK N/C LED driver controller or dimming controller input SRC 3V R1 R2 C1 10µF 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. 3.3V or 5V VDD VSS SNK N/C LED driver controller or dimming controller input 10µF SRC 3.3V PWM R1 40K R2 25K 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. Diable control CMOS Gate VDD VSS SNK N/C SRC 3.3V 60K 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 PWM 30K 10µF 30K LED driver controller or dimming controller input 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 ] = 25KΩ ∴ R1 = 11 * R2 = 275KΩ Figure 3 APPLICATIONS APPLICATIONS 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. The preceding examples represent just a few of the many ways the sensor can be used. For 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 the case of street lighting or operation of shades such a signal would engage the function when reaching the correct ambient light level. Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET RESPONSE VS WAVELENGTH 16 Amplitude (µW/cm 2) 14 12 10 8 6 4 2 0 0 ISRC STEP RESPONSE W WW . Microsemi . C OM 0.5 1 Tim e (Seconds) 1.5 2 VDD = 3.0V; RSRC = 25K & 4.7uF LINE REGULATION 22 21.5 SRC Current (µA) 21 20.5 20 19.5 19 3 3.5 4 4.5 VDD (V) 5 5.5 1000 Dark Current (nA) DARK CURRENT VS TEMP 100 3V 5V 5.5V 10 1 -40 -20 0 20 40 60 Temperature (ºC) 80 100 VDD = 3.5V; RSRC = 25K & 4.7uF RSRC = 25K & 4.7uF SNK OUTPUT PSRR 70 GAIN VS TEMP 1.15 1.1 Gain/Gain(25ºC) y = 1.35E-03x + 9.64E-01 60 PSRR (db) 1.05 1 0.95 0.9 0.85 50 40 CHARTS CHARTS 30 1 10 100 1000 10000 100000 Frequency (Hz) VDD = 3.0V; RSNK = 25K & 4.7uF 0.8 -50 0 50 Temperature (ºC) VDD = 3.0V Direct Light Input of 13.14µW/cm2 100 Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET SNK COMPLIANCE VS CURRENT 120 Output Current (µA) SRC COMPLIANCE VS CURRENT W WW . Microsemi . C OM 100 Output Current (µA) 0.1 0.2 0.3 0.4 0.5 100 80 60 40 20 0 SNK com pliance Voltage (V) VDD = 3.0V; RSNK = 25K & 4.7µF 80 60 40 20 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Source Com pliance Voltage (VDD-SRC) VDD = 3.0V; RSRC = 25K & 4.7µF SRC OUTPUT VS LUMINANCE(LUX) 160 Incandescent SRC OUTPUT VS LUMINANCE(LUX) 50 Incandescent 120 SRC (uA) SRC (uA) 0 3000 6000 9000 12000 15000 Luminance (lux) 18000 40 30 20 10 80 40 0 0 0 500 1000 1500 Luminance (lux) 2000 2500 VDD = 4.0V; RSNK = 10K & 4.7µF VDD = 4.0V; RSNK = 10K & 4.7µ C CHARTS Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET PACKAGE DIMENSIONS W WW . Microsemi . C OM DU 8-Pin Miniature Shrink Outline Package (MSOP) D Top View Dim A A1 b c D e E E1 L L1 S E1 S e E A A1 b L Side Views c L1 Θ Θ MILLIMETERS MIN MAX – 1.10 0.05 0.15 0.26 0.41 0.13 0.23 2.90 3.10 0.65 BSC 4.75 5.05 2.90 3.10 0.41 0.71 0.95 BSC 0.525 BSC 3° INCHES MIN MAX – 0.043 0.002 0.006 0.010 0.016 0.005 0.009 0.114 0.122 0.025 BSC 0.187 0.198 0.114 0.122 0.016 0.028 0.037 BSC 0.021 BSC 3° Active Area Required Minimum Light footprint Bonding / Wafer area A C Dim Active Area MILLIMETERS 1.22 0.60 0.60 2.5 INCHES 0.048 0.024 0.024 0.98 B C L Examination of Active Area A B C P1 Recommended light footprint pattern P1 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 MECHANICALS Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 LX1971 INTEGRATED PRODUCTS Wide Range Visible Light Sensor P RODUCTION D ATA S HEET NOTES W WW . Microsemi . C OM N 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. Copyright © 2003 Rev. 1.1b,2005-08-10 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9