19-4141; Rev 2; 5/09 KIT ATION EVALU E L B A IL AVA 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense Features The MAX16822A/MAX16822B step-down constant-current high-brightness LED (HB LED) drivers provide a cost-effective design solution for automotive interior/exterior lighting, architectural and ambient lighting, LED bulbs, and other LED illumination applications. The MAX16822A/MAX16822B operate from a +6.5V to +65V input-voltage range and can provide an output current up to 350mA, if operated up to a temperature of +125°C, or up to 500mA, if operated up to a temperature of +105°C. A high-side current-sense resistor adjusts the output current and a dedicated pulse-width modulation (PWM) input enables pulsed LED dimming over a wide range of brightness levels. ♦ High-Efficiency Solution These devices are well suited for applications requiring a wide input-voltage range. The high-side current sensing and an integrated current-setting circuitry minimize the number of external components while delivering an average output current with ±3% accuracy. A hysteretic control method ensures excellent input supply rejection and fast response during load transients and PWM dimming. The MAX16822A allows 10% current ripple and the MAX16822B allows 30% current ripple. Both devices operate up to a switching frequency of 2MHz, thus allowing the use of small-sized components. The MAX16822A/MAX16822B offer an analog dimming feature that reduces the output current by applying an external DC voltage below the internal 2V threshold voltage from TEMP_I to GND. TEMP_I also sources 25µA to a negative temperature coefficient (NTC) thermistor connected between TEMP_I and GND, thus providing an analog thermal-foldback feature that reduces the LED current when the temperature of the LED string exceeds a specified temperature point. An additional feature includes thermal-shutdown protection that turns off the LX driver when the junction temperature exceeds +165°C. The MAX16822A/MAX16822B operate over the -40°C to +125°C automotive temperature range and are available in an 8-pin SO package. ♦ Integrated High-Side Current Sense ♦ 6.5V to 65V Input-Voltage Range ♦ Output Current Up to 500mA ♦ On-Board 65V, 0.85Ω Power MOSFET ♦ Hysteretic Control: Up to 2MHz Switching Frequency ♦ ±3% LED Current Accuracy ♦ 200mV Current-Sense Reference ♦ Resistor-Programmable Constant LED Current ♦ Thermal-Foldback Protection/Linear Dimming ♦ Thermal-Shutdown Protection ♦ Available in an 8-Pin SO Package ♦ -40°C to +125°C Operating Temperature Range Ordering Information PART TEMP RANGE MAX16822AASA+ -40°C to +125°C 8 SO MAX16822BASA+ -40°C to +125°C 8 SO +Denotes a lead(Pb)-free/RoHS-compliant package. Typical Application Circuit D1 HB LEDs VIN RSENSE L1 C2 Applications 1 CS TEMP_I 8 Architectural, Industrial, and Ambient Lighting 2 Automotive RCL, DRL, and Fog Lights Heads-Up Displays PIN-PACKAGE IN C1 3 MAX16822A MAX16822B DIM GND LX PGND LX 7 NTC* ON OFF 6 Indicator and Emergency Lighting 4 Pin Configuration appears at end of data sheet. 5 *OPTIONAL ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX16822A/MAX16822B General Description MAX16822A/MAX16822B 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense ABSOLUTE MAXIMUM RATINGS IN, CS, LX, DIM to GND .........................................-0.3V to +70V TEMP_I to GND .......................................................-0.3V to +6V PGND to GND ......................................................-0.3V to +0.3V CS to IN .................................................................-0.3V to +0.3V Maximum Current into Any Pin (except IN, LX, and PGND).............................................20mA Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 7.4mW/°C above +70°C)...............588.2mW Junction-to-Ambient Thermal Resistance (θJA) (Note 1) ...136°C/W Pin-to-Pin ESD Ratings......................................................±2.5kV Operating Temperature Range 350mA (max) Output Current ........................-40°C to +125°C 500mA (max) Output Current ........................-40°C to +105°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, see www.maxim-ic.com/thermal-tutorial. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Input-Voltage Range CONDITIONS VIN MIN TYP 6.5 MAX UNITS 65 V Ground Current No switching 1.5 mA Supply Current VDIM < 0.6V, VIN = 12V 350 μA VCS = VIN - 100mV, VIN rising from 4V until VLX < 0.5VIN 6.25 UNDERVOLTAGE LOCKOUT (UVLO) Undervoltage Lockout UVLO 6.5 V VCS = VIN - 100mV, VIN falling from 6.5V until VLX > 0.5VIN 6 Undervoltage-Lockout Hysteresis 0.5 V SENSE COMPARATOR Sense Voltage Threshold High Sense Voltage Threshold Low VSNSHI VSNSLO MAX16822A, (VIN - VCS) rising from 140mV until VLX > 0.5VIN 201 210 216 MAX16822B, VIN - VCS rising from 140mV until VLX > 0.5VIN 218 230 236 MAX16822A, VIN - VCS falling from 260mV until VLX < 0.5VIN 185 190 198 MAX16822B, VIN - VCS falling from 260mV until VLX < 0.5VIN 166 mV mV 170 180 Propagation Delay to Output High tDPDH Falling edge of VIN - VCS from 140mV to 260mV to VLX = 0.5VIN 50 ns Propagation Delay to Output Low tDPDL Rising edge of VCS - VIN from 260mV to 140mV to VLX < 0.5VIN 50 ns CS Input Current ICSIN VIN - VCS = 200mV 2 _______________________________________________________________________________________ 3.5 μA 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense (VIN = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX VIN = VDIM = 24V, VCS = 23.9V, ILX = 350mA 0.85 1.7 VIN = VDIM = 6.0V, VCS = 5.9V, ILX = 350mA 1 2 UNITS INTERNAL MOSFET Drain-to-Source Resistance RDSON LX Leakage Current ILX_LEAK VDIM = 0V, VLX = 65V 10 μA DIM INPUT DIM Input-Voltage High DIM Input-Voltage Low DIM Turn-On Time VIH VIN - VCS = 100mV VIL VCS - VIN = 100mV tDIM_ON DIM Input Leakage High 2.8 0.6 VDIM rising edge to VLX < 0.5VIN V 200 VDIM = VIN VDIM = 0V DIM Input Leakage Low V ns -3 15 μA 0 μA THERMAL SHUTDOWN Thermal-Shutdown Threshold Temperature rising Thermal-Shutdown Threshold Hsysteresis 165 °C 10 °C THERMAL FOLDBACK Thermal-Foldback Enable Threshold Voltage VTFBON_THR VDIM = 5V Thermal-Foldback Slope FBSLOPE VDIM = 5V TEMP_I Output Bias Current 1.9 2.0 2.12 V 0.75 ITEMP_I 25 1/V 26.5 28 μA Typical Operating Characteristics (VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise noted.) 100 85 1 LED 80 75 70 15 LEDs 13 LEDs 80 70 7 LEDs 9 LEDs 5 LEDs 60 50 3 LEDs 1 LED 40 15 25 35 VIN (V) 45 55 65 90 13 LEDs 80 9 LEDs 60 7 LEDs 5 LEDs 50 40 30 20 20 10 10 15 LEDs 11 LEDs 70 30 3 LEDs 1 LED 0 0 5 100 FREQUENCY (kHz) 90 11 LEDs 90 DUTY CYCLE (%) EFFICIENCY (%) 95 11 LEDs13 LEDs 15 LEDs MAX16822A toc02 7 LEDs 9 LEDs 5 LEDs 3 LEDs MAX16822A toc01 100 FREQUENCY vs. VIN DUTY CYCLE vs. VIN MAX16822A toc03 EFFICIENCY vs. VIN 5 15 25 35 VIN (V) 45 55 65 5 15 25 35 45 55 65 VIN (V) _______________________________________________________________________________________ 3 MAX16822A/MAX16822B ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise noted.) QUIESCENT CURRENT vs. VIN NORMALIZED ILED vs. VIN 5 LEDs 7 LEDs 9 LEDs11 LEDs13 LEDs 15 LEDs 3 LEDs 1.00 1 LED 0.950 MAX16822A toc06 MAX16822A toc05 1.05 PWM DIMMING AT 200Hz DUTY CYCLE (10%) 500 450 QUIESCENT CURRENT (μA) MAX16822A toc04 1.10 NORMALIZED ILED 400 350 ILED 200mA/div 300 250 0 200 VDIM 5V/div 0 150 100 50 VIN = 48V 8 LEDs VDIM = 0V 0 0.90 0 5 10 15 20 25 30 35 40 45 50 55 60 65 0 5 10 15 20 25 30 35 40 45 50 55 60 65 VIN (V) VIN (V) 1ms/div PWM DIMMING AT 20kHz DUTY CYCLE (90%) PWM DIMMING AT 200Hz DUTY CYCLE (90%) MAX16822A toc08 MAX16822A toc07 ILED 200mA/div ILED 200mA/div 0 0 VDIM 5V/div 0 VDIM 5V/div 0 VIN = 48V 8 LEDs 1ms/div 10μs/div LED CURRENT vs. VTEMP_I ILED vs. TEMPERATURE 450 400 0.4 350 ILED (A) 300 250 0.3 0.2 200 150 0.1 100 50 VIN = 48V 0 0 0 0.4 0.8 1.2 1.6 VTEMP_I (V) 4 MAX16822A toc10 0.5 MAX16822A toc09 500 LED CURRENT (mA) MAX16822A/MAX16822B 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense 2.0 2.4 2.8 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) _______________________________________________________________________________________ 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense ITEMP_I vs. TEMPERATURE LXRDSON vs. TEMPERATURE 29.5 29.0 28.5 0.8 VIN = 48V VIN = 6.5V 0.7 0.6 ITEMP_ (μA) LXRDSON (Ω) 0.9 30.0 MAX16822A toc12 VIN = 65V MAX16822A toc11 1.0 28.0 27.5 27.0 26.5 26.0 0.5 25.5 25.0 0.4 VIN = 48V -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) Pin Description PIN NAME 1 CS Current-Sense Input. Connect a resistor between IN and CS to program the LED current. 2 IN Positive Supply Voltage Input. Bypass with a 1μF or higher value capacitor to GND. 3 GND 4 PGND 5, 6 LX 7 DIM 8 TEMP_I FUNCTION Ground Power Ground Switching Node Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to enable the current regulator. Thermal Foldback Control and Linear Input. Bypass with a 0.01μF capacitor to GND if thermal foldback or analog dimming is used. See the Thermal Foldback section for more details. Detailed Description The MAX16822A/MAX16822B are step-down, constantcurrent, high-brightness LED (HB LED) drivers. These devices operate from a +6.5V to +65V input-voltage range. The maximum output current is 500mA, if the part is used at temperatures up to +105°C, or 350mA, if it is used up to +125°C. A high-side current-sense resistor sets the output current and a dedicated PWM dimming input enables pulsed LED dimming over a wide range of brightness levels. A high-side current-sensing scheme and an on-board current-setting circuitry minimize the number of external components while delivering LED current with ±3% accuracy, using a 1% sense resistor. See Figure 1 for an internal block diagram. _______________________________________________________________________________________ 5 MAX16822A/MAX16822B Typical Operating Characteristics (continued) (VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C, unless otherwise noted.) MAX16822A/MAX16822B 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense IN VCC REGULATOR MAX16822A MAX16822B VCC _ANA ISET LX VCC _ANA CS CURRENT-SENSE COMPARATOR 0.85Ω, 65V DMOS SWITCH PWM DIMMING 1.23V BANDGAP REFERENCE GATE DRIVER UVLO COMPARATOR DIM DIM BUFFER VCC _ANA 25μA TEMP_I PGND VFTBON_THR 2V THERMAL FOLDBACK COMPARATOR GND Figure 1. Internal Block Diagram 6 _______________________________________________________________________________________ 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense DIM Input LED dimming is achieved by applying a PWM signal at DIM. A logic level below 0.6V at DIM forces the MAX16822A/MAX16822B’s output low, thus turning off the LED current. To turn the LED current on, the logic level at DIM must be greater than 2.8V. Thermal Shutdown The MAX16822A/MAX16822B thermal-shutdown feature turns off the LX driver when the junction temperature exceeds +165°C. The LX driver turns back on when the junction temperature drops 10°C below the shutdown-temperature threshold. Analog Dimming The MAX16822A/MAX16822B offer an analog dimming feature that reduces the output current when the voltage at TEMP_I is below the internal 2V threshold voltage. The MAX16822A/MAX16822B achieve analog dimming by either an external DC voltage source connected between TEMP_I and ground or by a voltage on a resistor connected across TEMP_I and ground induced by an internal current source of 25µA. When the voltage at TEMP_I is below the internal 2V threshold limit, the MAX16822A/MAX16822B reduce the LED current. Use the following formula to set the analog dimming current. ⎤ ⎡ ⎛ 1⎞ I TF (A) = ILED (A) × ⎢1 − FB SLOPE ⎜ ⎟ × VTFB _ ON − V A D (V) ⎥ ⎝ V⎠ ⎦ ⎣ ( ) where VTFB_ON = 2V and FBSLOPE = 0.75 are obtained from the Electrical Characteristics table and VAD is the voltage at TEMP_I. Selecting RSENSE to Set LED Current The LED current is programmed with a current-sense resistor connected between IN and CS. Use the equation below to calculate the value of this resistor: R SENSE (Ω) = where VSNSHI is the sense voltage threshold high and V SNSLO is sense voltage threshold low (see the Electrical Characteristics table for values). Current-Regulator Operation The MAX16822A/MAX16822B regulate the LED current using a comparator with hysteresis (see Figure 2). As the current through the inductor ramps up and the voltage across the sense resistor reaches the upper threshold, the internal MOSFET turns off. The internal MOSFET turns on again when the inductor current ramps down through the freewheeling diode until the voltage across the sense resistor equals the lower threshold. Use the following equation to determine the operating frequency: fSW = (VIN − nVLED ) × nVLED × R SENSE VIN × Δ V × L where n is the number of LEDs, VLED is the forward voltage drop of 1 LED, and ΔV = (VSNSHI - VSNSLO). Inductor Selection The MAX16822A/MAX16822B operate up to a switching frequency of 2MHz. For space-sensitive applications, the high switching frequency allows the size of the inductor to be reduced. Use the following formula to calculate an approximate inductor value and use the closest standard value: Thermal Foldback The MAX16822A/MAX16822B also include a thermalfoldback feature that reduces the output current when the temperature of the LED string exceeds a specified temperature point. These devices enter thermal-foldback mode when the voltage drop on the NTC thermistor, thermally attached to the LEDs and electrically connected between TEMP_I and ground, drops below the internal 2V threshold limit. 1 (VSNSHI + VSNSLO )(V) ILED (A) 2 L(approx.) = (VIN − nVLED ) × nVLED × R SENSE VIN × Δ V × fSW For component selection, use the MAX16822A/B Design Tool available at:www.maxim-ic.com/MAX16822software. _______________________________________________________________________________________ 7 MAX16822A/MAX16822B Applications Information Undervoltage Lockout (UVLO) The MAX16822A/MAX16822B include UVLO with 500mV hysteresis. The internal MOSFET turns off when VIN falls below 5.5V to 6.0V. MAX16822A/MAX16822B 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense HYSTERETIC MODE fSW ILED ΔI AVG. LED CURRENT t VDIM t2 t1 t Figure 2. Current-Regulator Operation Freewheeling-Diode Selection For stability and best efficiency, a low forward-voltage drop diode with fast reverse-recovery time and low capacitance is recommended. A Schottky diode is a good choice as long as its breakdown voltage is high enough to withstand the maximum operating voltage. PCB Layout Guidelines Careful PCB layout is critical to achieve low switching losses and stable operation. Use a multilayer board whenever possible for better noise immunity. Minimize ground noise by connecting high-current ground returns, the input bypass-capacitor ground lead, and 8 the output-filter ground lead to a single point (star ground configuration). In normal operation, there are two power loops. One is formed when the internal MOSFET is on and the high current flows through IN, RSENSE, LED load, the inductor, the internal MOSFET, and GND. The other loop is formed when the internal MOSFET is off and the high-current circulates through RSENSE, LED load, the inductor, and the freewheeling diode. Minimize each loop area to reduce noise interaction. Place RSENSE as close as possible to CS and IN. For better noise immunity, a Kelvin connection between CS and RSENSE is strongly recommended. _______________________________________________________________________________________ 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense Chip Information PROCESS: BiCMOS TOP VIEW + CS 1 8 IN 2 GND 3 MAX16822A MAX16822B PGND 4 Package Information TEMP_I For the latest package outline information, go to www.maxim-ic.com/packages. 7 DIM 6 LX PACKAGE TYPE PACKAGE CODE DOCUMENT NO. LX 8 SO S8-2 21-0041 5 SO _______________________________________________________________________________________ 9 MAX16822A/MAX16822B Pin Configuration MAX16822A/MAX16822B 2MHz, High-Brightness LED Drivers with Integrated MOSFET and High-Side Current Sense Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 5/08 Initial release — 1 6/08 Updated Ordering Information table to release MAX16822B. 1 2 5/09 Revised General Description, Features, Absolute Maximum Ratings, and Detailed Description. DESCRIPTION 1, 2, 5 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.