AL5801 100V, ADJUSTABLE CURRENT SINK LINEAR LED DRIVER Description Pin Assignments The AL5801 combines a 100V N-channel MOSFET with a pre- (Top View) biased NPN transistor to make a simple, small footprint LED driver. The LED current is set by an external resistor connected from REXT pin (4) to GND pin (6). The internal pre-biased transistor develops approximately 0.56V across the external resistor. The AL5801 open-drain output can operate from 1.1V to 100V enabling it to operate 5V to 100V power supplies without additional components. PWM dimming of the LED current can be achieved by driving the BIAS pin (1) with an external, open-collector NPN transistor or open-drain N-channel MOSFET. The AL5801 is available in a SOT26 package and is ideal for driving LED currents up to 350mA. SOT26 Features • Feedback Pin Reference Voltage VRSET = 0.56V at +25°C Applications • -40°C to +125°C Temperature Range • Linear LED Drivers • 1.1V to 100V Open-Drain Output • LED Signs • Negative temperature VRSET co-efficient automatically reduces • Offline LED Luminaries the LED current at high temperatures • Low thermal impedance SOT26 package with copper lead frame • Lead-Free Finish; RoHS Compliant (Notes 1 & 2) • Halogen and Antimony Free. “Green” Device (Note 3) • Qualified to AEC-Q101 Standards for High Reliability Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied. 2. See http://www.diodes.com for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free. 3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. Typical Applications Circuit AL5801 Document number: DS35555 Rev. 3 - 2 1 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 Pin Descriptions Pin Number Pin Name 1 BIAS Biases the open-Drain output MOSFET 2 3 4 FB OUT REXT 5 COMP Feedback pin Open-Drain LED driver output Current sense pin. LED current sensing resistor should be connected from here to GND Compensation pin. Connect COMP pin to REXT pin and insert a 1nF ceramic capacitor from COMP pin to FB pin for improved transient stability 6 GND Function Ground reference point for setting the LED current Functional Block Diagram Figure 1 Block Diagram Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) Symbol Values Unit VOUT Output voltage relative to GND Characteristics 100 V VBIAS BIAS voltage relative to GND (Note 4) 20 V FB voltage relative to GND 6 V VCOMP COMP voltage relative to GND 6 V VREXT REXT voltage relative to GND 6 V VFB 350 mA TJ Operating junction temperature -40 to +150 °C TST Storage temperature -55 to +150 °C IOUT Note: Output current 4. With pins 5 and 6 connected together. These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Operation at the absolute maximum rating for extended periods may reduce device reliability. AL5801 Document number: DS35555 Rev. 3 - 2 2 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 Package Thermal Data Characteristic Symbol Value 0.75 Power Dissipation (Note 5) @ TA = +25°C Power Dissipation (Note 6) @ TA = +25°C 0.70 PD Power Dissipation (Note 7) @ TA = +25°C 1.05 Thermal Resistance, Junction to Ambient Air (Note 5) @ TA = +25°C 165 Thermal Resistance, Junction to Ambient Air (Note 6) @ TA = +25°C 180 RθJA Thermal Resistance, Junction to Ambient Air (Note 7) @ TA = +25°C W 0.85 Power Dissipation (Note 8) @ TA = +25°C °C/W 145 120 Thermal Resistance, Junction to Ambient Air (Note 8) @ TA = +25°C Notes: Unit 5. Device mounted on 15mm x 15mm 2oz copper board. 6. Device mounted on 25mm x 25mm 1oz copper board. 7. Device mounted on 25mm x 25mm 2oz copper board. 8. Device mounted on 50mm x 50mm 2oz copper board. Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Symbol Min Max VBIAS Supply voltage range 3.5 20 VOUT OUT voltage range 1.1 100 ILED LED pin current (Note 9) 25 350 mA Operating ambient temperature range -40 125 °C TA Note: Parameter Unit V 9. Subject to ambient temperature, power dissipation and PCB. NMOSFET Electrical Characteristics: (Q1) (@TA = +25°C, unless otherwise specified.) Characteristic OFF CHARACTERISTICS Symbol Min Typ Max Unit Test Condition Drain-Source Breakdown Voltage BVDSS 100 ⎯ ⎯ V VGS = 0V, ID = 250µA Zero Gate Voltage Drain Current IDSS ⎯ ⎯ 1 µA VDS = 60V, VGS = 0V Gate-Source Leakage IGSS ⎯ ⎯ ±100 nA VGS = ±20V, VDS = 0V VGS(th) 2.0 ⎯ 4.1 V VDS = VGS, ID = 250µA RDS (ON) ⎯ ⎯ ⎯ 0.85 0.99 Ω VGS = 10V, ID = 1.5A VGS = 6V, ID = 1A ON CHARACTERISTICS Gate Threshold Voltage Static Drain-Source On-Resistance Forward Transconductance gfs ⎯ 0.9 ⎯ S VDS = 15V, ID = 1A Diode Forward Voltage VSD ⎯ 0.89 1.1 V VGS = 0V, IS = 1.5A DYNAMIC CHARACTERISTICS Ciss ⎯ 129 ⎯ pF Output Capacitance Coss ⎯ 14 ⎯ pF Reverse Transfer Capacitance Crss ⎯ 8 ⎯ pF Input Capacitance AL5801 Document number: DS35555 Rev. 3 - 2 3 of 11 www.diodes.com VDS = 50V, VGS = 0V f = 1.0MHz July 2012 © Diodes Incorporated AL5801 Pre-Bias Transistor Electrical Characteristics: (Q2) (@TA = +25°C, unless otherwise specified.) Characteristic (Note 10) Symbol Min Typ Max Unit VI(off) 0.4 - - V Input Voltage Test Condition VCC = 5V, IO = 100μA VI(on) - - 1.5 V VCC = 0.3V, IO = 5mA Output Voltage VO(on) - 0.05 0.3 V IO/II = 5mA/0.25mA Output Current IO(off) - - 0.5 μA VCC = 50V, VI = 0V DC Current Gain G1 80 - - - VO = 5V, IO = 10mA Input Resistance R1 3.2 4.7 6.2 kΩ - Resistance Ratio R2/R1 8 10 12 - - Notes: 10. Short duration pulse test used to minimize self-heating effect. 1.2 1.2 1.0 1.0 MAX POWER DISSIPATION (W) MAX POWER DISSIPATION (W) Thermal Characteristics 50mm x 50mm (2oz. FR4) 0.8 25mm x 25mm (2oz. FR4) 15mm x 15mm (2oz. FR4) 0.6 0.4 0.2 0 0 25 50 75 100 TEMPERATURE (°C) Figure 2 Derating Curve 125 TA = 25°C 2oz. FR4 0.8 0.6 0.4 0.2 0 150 0 500 1,000 1,500 2,000 2 COPPER AREA (mm ) Figure 3 Area vs. Max Power 2,500 180 JUNCTION TO AMBIENT AIR THERMAL RESISTANCE (°C/W) 160 140 T A = 25°C 25mm x 25mm 1oz. FR4 120 D = 0.5 100 80 D = 0.1 D = 0.2 60 D = 0.05 Single Pulse 40 20 0 0.0001 AL5801 Document number: DS35555 Rev. 3 - 2 0.001 0.01 0.1 1 10 PULSE WIDTH (s) Figure 4 Transient Thermal Impedance 4 of 11 www.diodes.com 100 1,000 July 2012 © Diodes Incorporated AL5801 Typical Performance Characteristics 0.40 400 Ibias = 0.1mA 0.30 300 0.25 250 0.20 0.15 200 150 REXT = 3.75Ω 0.10 100 0.05 0 Ibias = 0.1mA 350 REXT = 1.6Ω IOUT (mA) IOUT (A) 0.35 50 REXT = 11.6Ω REXT = 22.7Ω 0 1 2 VOUT (V) Figure 5 Output Current vs. VOUT 0 1 3 0.5 10 REXT (Ω) Figure 6 Output Current vs. REXT 0.20 TA = -40°C T A = -40°C 0.4 0.15 T A = 25°C TA = 25°C IOUT (A) 0.3 IOUT (A) 100 TA = 85°C 0.2 Ibias = 0.1mA 0.05 REXT = 1.6Ω 0.1 T A = 85°C 0.10 Ibias = 0.1mA REXT = 3.75Ω 0 0 1 2 VOUT (V) Figure 7 Output Current vs. VOUT 0 3 0.06 4 6 8 VOUT (V) Figure 8 Output Current vs. VOUT 10 TA = -40°C 0.030 T A = -40°C 0.05 0.025 IOUT (A) TA = 25° C IOUT (A) 2 0.035 0.07 0.04 TA = 85° C 0.03 0.02 TA = 25°C 0.020 T A = 85°C 0.015 0.010 Ibias = 0.1mA 0.01 0 0 0 5 10 VOUT (V) Figure 9 Output Current vs. VOUT AL5801 Document number: DS35555 Rev. 3 - 2 Ibias = 0.1mA 0.005 REXT = 11.6Ω 0 15 5 of 11 www.diodes.com REXT = 22.7Ω 0 5 10 15 VOUT (V) Figure 10 Output Current vs. VOUT 20 July 2012 © Diodes Incorporated AL5801 800 400 700 350 600 300 500 250 IOUT (mA) VREXT (mV) Typical Performance Characteristics (cont.) 400 150 200 100 Ibias = 0.1mA Vbias = 5V 0 -50 Document number: DS35555 Rev. 3 - 2 25mm x 25mm (2oz. FR4) 15mm x 15mm (2oz. FR4) 50 0 0 50 100 150 JUNCTION TEMPERATURE (°C) Figure 11 VREXT vs. Junction Temperature AL5801 50mm x 50mm (2oz. FR4) 200 300 100 Ibias = 0.1mA T A = 85°C 6 of 11 www.diodes.com 1 10 VOUT (V) Figure 12 Output Current vs. VOUT 100 July 2012 © Diodes Incorporated AL5801 Application Information Figure 13 Typical Application Circuit for Linear Mode Current Sink LED Driver The AL5801 is designed for driving high brightness LEDs with typical LED current up to 350mA. It provides a more cost effective way for driving low current LEDs when compared against more complex switching regulator solutions. Furthermore, it reduces the PCB board area of the solution because there is no need for external components like inductors, capacitors and/or switching diodes. Figure 13 shows a typical application circuit diagram for driving an LED or a string of LEDs. The NPN transistor Q2 measures the LED current by sensing the voltage across an external resistor REXT. Q2 uses its VBE as reference to set the voltage across REXT and controls the gate voltage of MOSFET Q1. Q1 operates in linear mode to regulate the LED current. The LED current is: ILED = VRSET / REXT where VRSET is the VBE of Q2. VBE is 0.56V typical at a +25°C device temperature. See Figure 11 for the variation of VBE with Q2’s junction temperature at IBIAS = 0.1mA. VBE has a negative temperature coefficient which reduces the LED current as the device warms up, protecting the LED(s). RBIAS should be chosen to drive 0.1mA current into the BIAS pin RBIAS = ( VCC – 3.75V ) / 0.1mA From the above equation, for any required LED current the necessary external resistor REXT can be calculated from REXT = VRSET / ILED The expected linear mode power dissipation must be factored into the design consideration. The power dissipation across the device can be calculated by taking the maximum supply voltage less the minimum voltage across the LED string. VDS(Q1) = VCC(max) – VLED(min) – VRSET PD = VDS(Q1) * ILED As the output LED current of AL5801 increases so will its power dissipation. The power dissipation will cause the device temperature to rise above ambient, TA, by an amount determined by the package thermal resistance, RθJA. Therefore, the power dissipation supported by the device is dependent upon the PCB board material, the copper area and the ambient temperature. The maximum dissipation the device can handle is given by: PD = ( TJ(MAX) - TA ) / RθJA TJ(MAX) = +150°C is the maximum device junction temperature. Refer to the thermal characteristic graphs in Figure 2 to 4 for selecting the appropriate PCB copper area. Figure 12 shows the current capabilities of the AL5801 at +25°C with different PCB copper area heat sinks. AL5801 Document number: DS35555 Rev. 3 - 2 7 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 Constant LED Current Temperture Compensation Variation in the junction temperature of Q2 will cause variations in the value of controlled LED current ILED. The base-emitter VBE voltage of Q2 decreases with increasing temperature at a rate of approximately 2mV/°C. Figure 14 shows a simple temperature compensation network, which comprises of an NTC thermistor and resistor Rbase, for stabilizing the LED current. Figure 14 Constant LED Current Temperature Compensation for AL5801 The voltage drop VRSET in the sense resistor REXT should be set to be 40 to 100mV higher than the VBE(Q2) at 25ºC. Figure 11 shows the typical VBE(Q2) is 0.56V at room temperature with 0.1mA IBIAS, so VRSET is selected to be 0.62V. With the VRSET chosen, the sense resistor value for 350mA ILED is determined by REXT = VRSET / ILED = 0.62V / 350mA = 1.77Ω So a standard resistor value of 1.78Ω with 1% tolerance is used. The RTH resistance of the NTC thermistor at room temperature is recommended as 10kΩ. The value of base resistor Rbase is set to be 470Ω. Q2’s base current is obtained as IB(Q2) = ( VRSET - VBE(Q2) ) / Rbase - VBE(Q2) / RTH = ( 0.62V - 0.56 ) / 470Ω - 0.56V / 10kΩ = 72µA T When VBE(Q2) is changed to VBE as the temperature increases to TºC, the thermistor resistance at T°C required to compensate this variation is given by T T T RTH = VBE / (( VRSET - VBE ) / Rbase - IB(Q2) ) At -2mV/°C, VBE(Q2) reduces to 0.44V from 0.56V as the temperature increases from +25°C to +85°C. From the above equation, the thermistor’s resistance at +85°C to keep the same output current is given by 85 RTH = 0.44V / (( 0.62V – 0.44V ) / 470Ω - 72µA ) = 1.4kΩ The NTC thermistor is chosen for compensation whose resistance is 10kΩ at +25°C and 1.38kΩ at +85°C with a β value of 3530. Figure 15 shows the ILED variation with temperature with and without temperature compensation. Figure 15 LED Current Variation with and without Temperature Compensation AL5801 Document number: DS35555 Rev. 3 - 2 8 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 PWM Dimming (b) (a) Figure 16 Application Circuits for LED Driver with PWM Dimming Functionality (a) MOSFET driving and (b) Transistor driving PWM dimming can be achieved by driving the BIAS pin (1). An external open-collector NPN transistor or open-drain N-channel MOSFET can be used to drive the BIAS pin as shown in Figure 16. Dimming is achieved by turning the LEDs ON and OFF for a portion of a single cycle. The PWM signal can be provided by a micro-controller or by analog circuitry. Figure 17 shows the LED current against the PWM signal duty ratio when the AL5801 is used to drive three series connected LEDs from a 12V supply. The PWM dimming frequency is set to 200Hz. The PWM signal is supplied to the open-Drain small signal MOSFET’s gate as shown in Figure 16a. The BIAS pin signal is an inversion of the PWM drive to the MOSFET’s gate. Therefore, a PWM signal duty cycle of 0% provides the maximum LED current. Sufficiently large PCB copper area is used for heat sinking of the AL5801 in order to minimize the device self-heating at +25°C ambient. Figure 17 LED Current against PWM Dimming Signal Duty Ratio at 200Hz PWM Frequency AL5801 Document number: DS35555 Rev. 3 - 2 9 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 Ordering Information Green Green 7” Tape and Reel Part Number Qualification Package Code Packaging (Note 11) Quantity Part Number Suffix AL5801W6-7 AL5801W6Q-7 Commercial Automotive W6 W6 SOT26 SOT26 3,000/Tape & Reel 3,000/Tape & Reel -7 -7 Notes: 11. For packaging details, go to our website at http://www.diodes.com Marking Information L100 = Product Type Marking Code YM = Date Code Marking Y = Year (ex: Y = 2012) M = Month (ex: 9 = September) Date Code Key Year Code Month Code Jan 1 2012 Z 2013 A Feb 2 Mar 3 2014 B Apr 4 May 5 2015 C Jun 6 2016 D Jul 7 Aug 8 2017 E Sep 9 Oct O 2018 F Nov N Dec D Package Outline Dimensions (All dimensions in mm.) A B C H K M J L D SOT26 Dim Min Max Typ A 0.35 0.50 0.38 B 1.50 1.70 1.60 C 2.70 3.00 2.80 D ⎯ ⎯ 0.95 H 2.90 3.10 3.00 J 0.013 0.10 0.05 K 1.00 1.30 1.10 L 0.35 0.55 0.40 M 0.10 0.20 0.15 0° 8° α ⎯ All Dimensions in mm Suggested Pad Layout C2 Z C2 Dimensions Value (in mm) Z 3.20 G 1.60 X 0.55 Y 0.80 C1 G C1 C2 Y 2.40 0.95 X AL5801 Document number: DS35555 Rev. 3 - 2 10 of 11 www.diodes.com July 2012 © Diodes Incorporated AL5801 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. 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Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. 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