LX1971 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET KEY FEATURES DESCRIPTION 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. IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com Protected By U.S. Patents: 6,787,757; Patents Pending 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 WWW . 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. BENIFITS • Requires no wavelength filters • Insensitive to UV and IR • More than 4 decades usable light range • Enables accurate lighting control systems PRODUCT HIGHLIGHT VDD 4.7uF VDD 25K SNK SNK 0.60V Typ LX1971 VOUT SRC 4.7uF 25K 0.45V Typ SRC GND Ambient Light 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 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET PACKAGE PIN OUT 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 VDD 1 8 VSS NC 2 7 NC NC 3 6 NC SRC 4 5 SNK 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. DU PACKAGE (Top View) Solder reflow to follow: IPC/JEDEC J-STD-020B 7/02 Pb-SN Small Body Profile 1 8 DU 6 1971 THERMAL DATA xxxx 7 5 Plastic MSOP 8-Pin THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA 206°C/W 39°C/W THERMAL RESISTANCE-JUNCTION TO CASE, θJC WWW . Microsemi .C OM ABSOLUTE MAXIMUM RATINGS 2 3 4 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 DESCRIPTION VDD Input Supply Voltage VSS Ground Reference for Power and Signal Output SNK Output Current Sink SRC Output Current Source SIMPLIFIED BLOCK DIAGRAM PACKAGE PHOTO V DD 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 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET Parameter LX1971 Typ Min Supply Voltage (VDD ) Max WWW . Microsemi .C OM RECOMMENDED OPERATING CONDITIONS Units 3¹ 5.5 V SNK Compliance Voltage Range VSS +0.6 VDD V SRC Compliance Voltage Range VSS VDD - 0.75 V SNK/SRC Output Resistor Range 5 100 KΩ ¹Outputs are functional down to VDD=2.7V 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 Symbol Supply Voltage Range VDD Input Supply Current IDD ISRC ISRC Output Current ISNK ISRC ISRC Output SNK/SRC Current Matching IMATCH Test Conditions Min LX1971 Typ 3 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 Max Units 5.5 VDC 350 590 750 µA 55 61 67 µA 52 61 70 -70 -61 -52 µA 34 41 48 µA 5.5 7 8.5 µA 2 6 % VSS +0.45 VSS +0.6 V VDD – 0.6 VDD – 0.7 V VDD = 3.0V VDD = 3.0V, @ 95% of nominal output current VDD = 3.0V, @ 95% of nominal output current SNKVMIN SRC Maximum Compliance Voltage SRCVMAX SNK/SRC Output Dark Current IDARK3.0V VDD = 3V, No Light, 25°C 150 400 nA SNK/SRC Output Dark Current IDARK3.0V VDD = 3V, No Light, -40°C to 70°C 450 1000 nA SNK/SRC Output Dark Current IDARK3.0V VDD = 3V, No Light, 85°C 550 1150 nA SNK/SRC Output Dark Current IDARK5.5V VDD = 5.5V, No Light, 25°C 320 nA Wavelength of Peak Sensitivity λPS 520 nm Half Reception Angle θ½ ±60 deg Supply Voltage Coefficient of Output Current Resolution Limit Due To Random Noise Sensitivity Change @ 910nm Radiant Sensitive Area PSRR IMIN ISRC∆ IR A VDD = 3V to 5.5V 2.9 Minimum usable resolution 146 Current responsivity change with 2 additional direct light input of 584µW/cm at 910nm, TA = 25°C, VDD = 3V Photodiode Area -10 0 .369 3.5 %/V nW/cm 10 2 % of peak mm 2 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 ELECTRICALS SNK Minimum Compliance Voltage LX1971 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET 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. I OUT = ( LX1971 Calculated SRC Full Range Response 250 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. WWW . Microsemi .C OM APPLICATION INFORMATION 200 150 100 50 0 0 ) 5000 10000 15000 20000 25000 Incandescent Light (lux) L × .808 + 1.1µA for L < 2500 lux <2500 Lux Formula I OUT = (L × .0083µA) + 23µA for 2500 lux < L < >2500 Lux Formula LX1971 Calculated SRC Low Level Response 20000 lux 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. SRC Current (µA) 40 30 20 10 0 0 500 1000 1500 2000 2500 Incandescent Light (lux) <2500 Lux Formula LX1971 Calculated SRC High Level Response 250 APPLICATIONS 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. 50 SRC Current (µA) 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. 200 150 100 50 0 0 5000 10000 15000 20000 25000 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 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET 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. 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 N/C SNK VSS SRC LED driver controller or dimming controller input 10µF 3.3V PWM R1 40K 3.3V or 5V WWW . Microsemi .C OM APPLICATION EXAMPLES R2 25K VDD VSS SNK N/C Figure 2 SRC 3V R1 R2 C1 10µF 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. LED driver controller or dimming controller input Diable control Figure 1 CMOS Gate 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. VDD VSS SNK N/C SRC 3.3V 60K PWM 30K 10µF 30K LED driver controller or dimming controller input R1 = R2 [ 3.0V/0.25V –1] = 11 * R2 R2 = [ 1.25V / 50uA ] = 25KΩ ∴ R1 = 11 * R2 = 275KΩ 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. Copyright © 2003 Rev. 1.1b,2005-08-10 Figure 3 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. Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 APPLICATIONS 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: LX1971 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET ISRC STEP RESPONSE WWW . Microsemi .C OM RESPONSE VS WAVELENGTH Amplitude (µW/cm 2) 16 14 12 10 8 6 4 2 0 0 0.5 1 Tim e (Seconds) 1.5 2 VDD = 3.0V; RSRC = 25K & 4.7uF LINE REGULATION DARK CURRENT VS TEMP 22 1000 Dark Current (nA) SRC Current (µA) 21.5 21 20.5 20 100 3V 5V 5.5V 10 19.5 1 -40 19 3 3.5 4 4.5 VDD (V) 5 5.5 -20 0 20 40 60 Temperature (ºC) 80 100 RSRC = 25K & 4.7uF VDD = 3.5V; RSRC = 25K & 4.7uF SNK OUTPUT PSRR GAIN VS TEMP 70 1.15 y = 1.35E-03x + 9.64E-01 1.1 Gain/Gain(25ºC) 50 40 1.05 1 0.95 CHARTS PSRR (db) 60 0.9 0.85 30 0.8 1 10 100 1000 10000 100000 Frequency (Hz) 0 50 Temperature (ºC) 100 VDD = 3.0V Direct Light Input of 13.14µW/cm2 VDD = 3.0V; RSNK = 25K & 4.7uF Copyright © 2003 Rev. 1.1b,2005-08-10 -50 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LX1971 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET SNK COMPLIANCE VS CURRENT SRC COMPLIANCE VS CURRENT 100 100 Output Current (µA) Output Current (µA) WWW . Microsemi .C OM 120 80 60 40 20 0 80 60 40 20 0 0.1 0.2 0.3 0.4 0.5 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Source Com pliance Voltage (VDD-SRC) SNK com pliance Voltage (V) VDD = 3.0V; RSNK = 25K & 4.7µF VDD = 3.0V; RSRC = 25K & 4.7µF SRC OUTPUT VS LUMINANCE(LUX) SRC OUTPUT VS LUMINANCE(LUX) 160 50 Incandescent Incandescent 40 SRC (uA) SRC (uA) 120 80 30 20 40 10 0 0 0 3000 6000 9000 12000 15000 Luminance (lux) 18000 VDD = 4.0V; RSNK = 10K & 4.7µF 0 500 1000 1500 Luminance (lux) 2000 2500 VDD = 4.0V; RSNK = 10K & 4.7µ 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 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET PACKAGE DIMENSIONS WWW . Microsemi .C OM DU 8-Pin Miniature Shrink Outline Package (MSOP) D Top View 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° MILLIMETERS INCHES A B C 1.22 0.60 0.60 0.048 0.024 0.024 P1 2.5 0.98 Dim E1 S e E A A1 c L1 L b Θ A A1 b c D e E E1 L L1 S Θ Side Views Active Area Required Minimum Light footprint Bonding / Wafer area Dim A Active Area C B C L Examination of Active Area Recommended light footprint pattern 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 MECHANICALS 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. Page 8 LX1971 I N T E G R A T E D Wide Range Visible Light Sensor P R O D U C T S P RODUCTION D ATA S HEET WWW . Microsemi .C OM NOTES 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