LX1990 Dual Programmable LED Current Sink ® TM DESCRIPTION • Programmable Sink Current 0.1 to 30mA x 2 Channels • Replaces Discrete Transistor Circuitry With A Single Package • 300mV Maximum Current Sink Dropout Voltage at 20mA • 2.7 to 5.5V Power Supply Input • IOUT Compliance Voltage from 0.1 to 10VDC • Enable Input With <1µA Sleep Current • Amplitude and PWM Dimming • Current rise and fall time may be controlled to reduce EMI bs ol et e Light output from LED’s is proportional to average current through them; they can easily produce a brightness range of 500:1. However, color of emitted light is shifted by current amplitude. Color shift at low light levels can be reduced by driving the LED’s with a constant peak current while dimming with duty cycle control. This is achieved by driving the ISET resistor with a PWM signal. A 500:1 brightness range can be achieved by choosing 270 Hz as the PWM frequency (to avoid optical beating with 50/60 Hz room lights) and pulse width from 3.7 milliseconds to 7.4 microseconds. The LX1990 features a shutdown mode via the Enable pin. In this mode the LX1990 consumes less than 1µA and holds the two open collector output stages off. This pin may also be used to pulse width modulate output current. See applications section for dimming details. IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com WWW . Microsemi .C OM The LX1990 is a dual output current sink optimized for driving light emitting diodes. This low cost bipolar IC enables precise current regulation in LED display lighting applications, yet requires far fewer parts than discrete solutions. The LX1990 is supplied in a micro-miniature 6 lead MLP package featuring a 3 x 3 mm footprint, a profile of less than 1mm, and much improved thermal performance. Its two output sink currents are accurately matched and require only one resistor to program. Program current is only 1% of the output currents, and quiescent current is low, providing a very high efficiency driver for battery-powered displays. The LX1990 is based on a currentmirror architecture that transfers a reference current produced at the ISET pin to each of two open-collector current sinking outputs. The output stages multiply this reference current by 100 to sink independently regulated currents up to 30 mA. KEY FEATURES APPLICATIONS • Cell Phone Display Illumination • PDA White LED Display Lighting • Automotive Display Illumination • Digital Still Camera • Camcorders • Consumer Electronics Front Panels PRODUCT HIGHLIGHT 5V V LO AD VDD ENA IO U T B LX1990 I O UT A ISET G ND R SET TA (°C) LX1990 O O N/OFF PACKAGE ORDER INFO Plastic MLP LM 6-Pin RoHS Compliant / Pb-free Transition DC: 0452 -40 to 85 LX1990ILM Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1990ILM-TR) Copyright © 2001 Rev. 1.0d, 2005-03-14 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LX1990 Dual Programmable LED Current Sink ® TM ABSOLUTE MAXIMUM RATINGS PACKAGE PIN OUT ISET 1 6 I OUTA VDD 2 5 GND ENA 3 4 I OUTB WWW . Microsemi .C OM LM PACKAGE bs ol et e Supply Voltage (VDD) ....................................................................................... 6V ENA Voltage..................................................................................................... 6V ISET Maximum Current.............................................................. Internally Limited ISET Maximum Voltage .................................................................................. VDD IOUT Maximum Compliance Voltage ...............................................................12V Current Source Outputs.............................................................................. 100mA Operating Temperature Range .........................................................-40°C to 85°C Maximum Junction Temperature ................................................................. 125°C Storage Temperature......................................................................-65°C to 150°C Peak Package Solder Reflow Temperature (40 seconds maximum exposure).................................................... 260°C (+0, -5) (Top View) 1990 xxxx LMI Note: 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. LM PACKAGE MARKINGS THERMAL DATA xxxx – Denotes Date Code / Lot Identification RoHS / Pb-free 100% Matte Tin Lead Finish LM Plastic MLP 6-Pin THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA 41°C/W Junction Temperature Calculation: TJ = TA + (PD x θJA). The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. FUNCTIONAL PIN DESCRIPTION NAME VDD GND DESCRIPTION Input Supply Common ground reference Chip Enable Input. If logic high, current source outputs are enabled. If logic low, internal power is disconnected from the VDD pin, disabling all functions. Logic threshold is 1.2 V. IOUTA & IOUTB Output Current Source. Two separate constant current outputs. Outputs may be loaded in any combination without affecting regulation of the loaded output. If only one output is needed IOUTA & IOUTB must be shorted together. In this case the value of ISET resistor must be doubled. Compliance voltage range is 0.1V to 10V. ISET Output current programming pin. Copyright © 2001 Rev. 1.0d, 2005-03-14 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 PACKAGE DATA O ENA Page 2 LX1990 Dual Programmable LED Current Sink ® TM Parameter Min Units Max 2.7 5.5 V ENA (ENABLE) Input Voltage 0 VDD V ISET Voltage 0 1.25 V ISET Current 0 300 µA IOUTA / IOUTB Compliance Voltage Range 0.1 10 V IOUTA / IOUTB Output Current Range 0.1 30 mA bs ol et e Supply Voltage (VDD) LX1990 Typ WWW . Microsemi .C OM RECOMMENDED OPERATING CONDITIONS ELECTRICAL CHARACTERISTICS Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C ≤ TA ≤ 85°C and the following test conditions: VDD = 2.7 to 5.5 VDC, ISET = 200µA, VOUT ≤ 5.5V, VLOAD ≤ 10V. Typical values are at TA= 25°C Parameter Symbol Test Conditions Min LX1990 Typ Max Units Power Characteristics Quiescent Current I_QUI VDD = 2.7V; ISET = 0uA 1.4 2 mA Quiescent Current I_QUI VDD = 5.5V; ISET = 300uA 3.0 4 mA 0.08 1 µA 1.55 2.4 V 4 10 µA Sleep Current 1 I_SLEEP VDD = 5.5V, ENA ≤ 0.4V Enable Input Enable Logic Threshold VTH_EN Enable Input Current IIN_EN 0.8 ENA = VDD = 5.5V ISET to Out Pulse Response TD(ON) 1.2 2 µS ISET to Out Pulse Response TD(OFF) 1.4 2 µS 300 µA 1.25 1.275 VDC ISET Input ISET Current Range IISET RSET terminated to GND ISET Voltage VISET ISET = 200uA 1.225 0 0.5 < VOUT < 5.5V, ISET = 200µA 18.5 Output Current Amplitude 20 21.5 mADC OUTA to OUTB Current Matching IOUT_MATCH IOUT = 20mA ; (IOUTA – IOUTB ) / IOUTA * 100 0.4 5 % ISET to IOUT Current Ratio IOUT_RATIO IOUT/ISET; ISET = 200µA ; VDD = 5.5V 102 ISET to IOUT Current Ratio IOUT_RATIO IOUT/ISET; ISET = 200µA ; VDD = 2.7V 99 Output Current ISET = 0µA IOUT_ZERO 0.5 < VOUT < VLOAD, ISET = 0µA 10 100 µADC Dropout Voltage 2 VDROPOUT IOUT = 20mA 150 300 mV Dropout Voltage 2 VDROPOUT IOUT = 30mA 200 400 mV VISET = Zero Volts; VDD=5V 100 Maximum Output Current, ISET Shorted To Gnd. Each Output IOUT ISC Output Off State Current IOUTOFF 20 ENA ≤ 0.4V 1 At enable voltages greater than 0.4V but less than 0.8V the outputs will remain off but the sleep current may be greater than 1µA. 2 Dropout is defined as the OUTA/B to GND voltage at which the output current sink drops 10% from the nominal value. Copyright © 2001 Rev. 1.0d, 2005-03-14 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 mADC µADC Page 3 ELECTRICALS O Output Characteristics LX1990 ® TM Dual Programmable LED Current Sink I OUTA VDD WWW . Microsemi .C OM SIMPLIFIED BLOCK DIAGRAM I OUTB bs ol et e 1:1 Current Mirror 100X 100X + 1.25V REF - ENABLE Bias ISET GND Copyright © 2001 Rev. 1.0d, 2005-03-14 BLOCK DIAGRAM O Figure 1 – Simplified Block Diagram Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LX1990 ® TM Dual Programmable LED Current Sink n IOUT VLOAD VLED PD = = = = = Number of outputs used Current from each output Output Supply Voltage Minimum LED forward voltage Power Dissipated in mW When the ENA input is at zero volts, less than 20µA current flows into or out of the outputs. If the disable function is used , ENA must be driven below 0.4 volts to insure minimum current from VDD. bs ol et e FUNCTIONAL DESCRIPTION The LX1990 is designed to drive LED’s used in display illumination and signaling applications such as cellular telephones and PDA’s. With a 5V supply, the two independently regulated constant current outputs can drive 2 white LED’s (VF < 4.5V) in parallel, or 4 green or amber LED’s (VF < 2.25V each) arranged as 2 parallel x 2 in series. With Dropout voltage of only 300 mV at 20 mA, the LX1990 provides regulated current for 2 green / amber LED’s in a cell phone all the way down to the minimum NiCd cutoff of 2.7 volts for three cells. The LX1990 features resistor settable output current. Connecting a resistor between ISET and a voltage of zero to 1.25 volts generates a current that is mirrored into each of the output with a gain of about 100. Output current can be varied in an analog fashion by varying ISET resistance or termination voltage (see application schematics). Duty cycle dimming with a fixed current amplitude is accomplished by switching the ISET current on and off with an open collector or open drain pulse width modulated logic signal. Switching frequency can exceed 20 KHz, making it practical to use a PWM output channel from popular micro controllers. The upper limit on frequency is minimum switching response from ISET to output. As frequency increases, these fixed delays will cause an error in expected output current duty cycle. APPLICATION NOTES Each output has an independent current sink, however both must be held above about 0.5 volts to maintain specified current regulation accuracy. If only one output is needed, the two outputs should be connected together and the programming resistor value doubled so each output supplies ½ the desired current. In this case, more than 60 mA total current can be delivered from the combined output. Package power dissipation can be calculated from the following equation: PD = (n⋅ I OUT ) ⋅ (VLOAD − VL ED ) Copyright © 2001 Rev. 1.0d, 2005-03-14 The ISET pin may be driven with a digital open collector or open drain logic PWM signal to dim the LED’s. Recommended PWM frequency for dimming is between 100 Hz and 20 KHz. Below 100 Hz flicker may be observed. Above 20 KHz duty cycle accuracy is reduced due to switching delays from ISET to outputs. Totem pole output drive may also be used as long as the maximum driver voltage never exceeds the VDD supply. Since the totem pole drive will exceed the 1.25V ISET voltage it can introduce delays that may limit the useful frequency and maximum dim range. If PWM dimming is used, use separate power and ground lines directly from the power source point to prevent noise generated from the LED current transients from entering video or audio subsystems on the same supply rails. Additional power supply filtering may be needed in PWM dimming applications. Care should be exercised in the PCB layout to prevent coupling from the outputs to the ISET pin, as this may cause the part to oscillate. Current out of the ISET pin may be varied for current amplitude dimming. There are two ways to do this: If a mechanical input is needed, a rheostat in series with a resistor connected from GND to ISET can be used. The second method is to connect a fixed resistor from ISET to the output of a voltage DAC or other low impedance voltage source. Varying the voltage between zero and 1.25 volts will cause a corresponding output current change from IOUT max to zero: I OUT = Current Ratio × ISET The ENA pin may be used to duty cycle dim the output in applications where only one control line is available for dimming and shutdown. A narrow current spike that may be as high as 100 mA is produced when the ENA signal has very fast rise times. This is not harmful to the LED, but will cause dimming linearity errors when operating at very low duty cycles. Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 APPLICATIONS O All inputs and outputs are ESD and short circuit protected making the LX1990 an exceptionally robust component. However it is not recommended to indefinitely short the ISET input to ground while shorting the outputs to 10V as the power dissipation under these conditions is the greatest. WWW . Microsemi .C OM APPLICATIONS LX1990 ® TM Dual Programmable LED Current Sink WWW . Microsemi .C OM TYPICAL CHARACTERISTICS VDD = 5V, ENA = 5V, ISET = 200µA, TA = 25°C. Unless otherwise noted. IOUT Vs. Temperature @ ISET = 200µA Output Off Leakage Current vs.VOUT ENA=0.4V 14 20.8 IOUTA @ 5V 12 IOUTB @ 5V 20.4 20.2 20 19.8 IOUT Leakage (µA) 5.5V IOUT A @ 2.7V 5V 8 6 4 2.7V 2 IOUTB @ 2.7V 19.6 10 bs ol et e IOUT Current (mA) 20.6 0 -45 -20 5 30 55 80 105 0 130 2 4 Tem p (°C) IOUT vs ISET 45 40 35 20 15 10 5 0 10 12 VDROPOUT vs. Current 5.5V 5V 30 30mA 25 IOUT (mA) IOUT (mA) 25 8 35 2.7V 30 6 V OUT (V) 25mA 20 20mA 15 15mA 10 10mA 5 5mA 0 0 50 100 150 200 250 300 350 0.1 400 ISET (µA) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Dropout (V) Output Current vs. VDD O Enable to Output Response 20.7 ENA 2V / DIV 20.5 AOUT 20.4 CHARTS Output Current (mA) 20.6 20.3 BOUT 20.2 20.1 IOUT 10mA / DIV 20 19.9 2.7 3.7 4.7 5.7 VDD (V) Copyright © 2001 Rev. 1.0d, 2005-03-14 10µs / DIV Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LX1990 Dual Programmable LED Current Sink ® TM 3.3V V LO AD VDD I O UTB Figure 2 – Auto Dashboard or Instrument Front Panel LED Array ON/OFF bs ol et e ENA I O UTA ISET GND .1µF 4K WWW . Microsemi .C OM APPLICATIONS O pen Collector or Open Drain Drive +5V .1µF GRN W HT VDD I O UTB GRN ON/OFF ENA I O UTA ISET GND 1.25V 4K D0 D1 O UT D2 D3 Up to 10 Volts Figure 3 – Color LCD Display & Keypad Illumination LOAD VDD I O UTB APPLICATIONS O +5V ENA I O UTA ON/OFF ISET G ND 100K 4K Figure 4 – Variable Current Driver Copyright © 2001 Rev. 1.0d, 2005-03-14 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LX1990 Dual Programmable LED Current Sink ® TM VDD IOUTB VDD IOUTB PWM ON / OFF ENA IOUTA 3V VDD IOUTB ENA IOUTA ENA IOUTA ISET GND ISET GND WWW . Microsemi .C OM DIMMING METHODS ISET GND bs ol et e RMIN RSET RSTEP RMAX RMIN Figure 5 – PWM on Enabled (Lowest IQ) Figure 6 – Precision 2 Steps Figure 7 – Manual Control ON / OFF VDD IOUTB ON / OFF VDD IO UTB VDD IOUTB ENA IOUTA ENA IOUTA 6.3K ENA IO UTA 1K CSLOPE ISET GND R SET ISET GND ISET GND 8.2nF 5K PWM 2N2222A PWM 2N2222 10K 10K PW M 100K 10mA / DIV 10µs / DIV Figure 8 – PWM Dimming Totem Pole Output Copyright © 2001 Rev. 1.0d, 2005-03-14 1V / DIV 1V / DIV 10µA / DIV 10mA / DIV 20µs / DIV Figure 9 – PWM – Low EMI Wide Range 20µs / DIV Figure 10 – PWM – Wide Range 500:1 + Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 APPLICATIONS O 1V / DIV 100K LX1990 ® TM Dual Programmable LED Current Sink WWW . Microsemi .C OM APPLICATION 48V .47µF 10 W hite LEDs each output bs ol et e Optional circuit for higher efficiency LX432SC BC846B x2 2.2K 3.3V VDD I OUTB 20K ENA I OUTA ON/OFF 20K ISET GND R SET PW M 10K 100K Copyright © 2001 Rev. 1.0d, 2005-03-14 APPLICATIONS O Figure 11 – Using the LX1990 With High Voltage Supplies Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9 LX1990 Dual Programmable LED Current Sink ® TM LM 6-Pin Plastic MLP-Micro Exposed Pad Dim A J E B H I C G F Internally Connected together, but isolated from all other terminals Note: 1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006”) on any side. Lead dimension shall not include solder coverage. Copyright © 2001 Rev. 1.0d, 2005-03-14 MECHANICALS O D A B C D E F G H I J K INCHES MIN MAX 0.114 0.122 0.114 0.122 0.025 0.029 0.005 0.009 0.075 BSC 0.010 0.016 0.037 BSC 0.048 BSC 0 0.003 0.008 0.014 0 0.003 bs ol et e K MILLIMETERS MIN MAX 2.90 3.10 2.90 3.10 0.65 0.75 0.15 0.25 1.841 BSC 0.27 0.43 0.95 BSC 1.22 BSC 0 0.10 0.21 0.37 0 0.10 WWW . Microsemi .C OM PACKAGE DIMENSIONS Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 10 LX1990 ® TM Dual Programmable LED Current Sink O bs ol et e 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 © 2001 Rev. 1.0d, 2005-03-14 Microsemi Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11