19-4028; Rev 1; 5/08 High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver The MAX16835 current regulator operates from a 6.5V to 40V input voltage range and delivers up to a total of 350mA to one or more strings of high-brightness LEDs (HB LEDs). The output current of the MAX16835 is adjusted by using an external current-sense resistor in series with the LEDs. An enable input allows widerange “pulsed” dimming. Wave-shaping circuitry reduces EMI. The differential current-sense input increases noise immunity. The MAX16835 is well suited for applications requiring high-voltage input and is able to withstand automotive load-dump events up to 40V. An on-board pass element minimizes external components while providing ±3.5% output current accuracy. Additional features include a 5V regulated output and short-circuit and thermal protection. The MAX16835 is available in a thermally enhanced, 5mm x 5mm, 16-pin TQFN package and is specified over the automotive -40°C to +125°C temperature range. Applications Automotive Interior: Map, Courtesy, and Cluster Lighting Features o o o o o o o o o o o o o o +6.5V to +40V Operating Range Adjustable LED Current (35mA to 350mA) ±3.5% Output Current Accuracy Integrated Pass Element with Low-Dropout Voltage (0.55V typ) Output Short-Circuit Protection +5V Regulated Output with 4mA Source Capability Thermal Shutdown Differential LED Current Sense High-Voltage Enable Pin for Dimming Interface Low Shutdown Supply Current (35µA typ) Low 200mV Current-Sense Reference Reduces Power Losses Wave-Shaped Edges Reduce Radiated EMI During PWM Dimming Available in Small, Thermally Enhanced, 5mm x 5mm, 16-Pin TQFN Package -40°C to +125°C Operating Temperature Range Automotive Exterior: Tail Lights and CHMSL Ordering Information Warning Lights for Emergency Vehicles PART Navigation and Marine Indicators TEMP RANGE MAX16835ATE+ General Illumination -40°C to +125°C +Denotes a lead-free package. *EP = Exposed pad. Signage, Gasoline Canopies, Beacons GND V5 CS- CS+ Pin Configuration TOP VIEW 12 11 10 9 PIN-PACKAGE 16 TQFN-EP* Simplified Diagram +6.5V TO +40V IN OUT 0.1μF 8 N.C. 13 +5V REG N.C. V5 LEDs 0.1μF N.C. 14 MAX16835 EN 15 OUT 16 + 7 N.C. 6 N.C. 5 N.C. MAX16835 CS+ RSENSE PWM DIMMING 2 3 4 OUT IN IN N.C. EN 1 CSGND TQFN ________________________________________________________________ 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 MAX16835 General Description MAX16835 High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver ABSOLUTE MAXIMUM RATINGS IN to GND ...............................................................-0.3V to +45V OUT, EN to GND..........................................-0.3V to (VIN + 0.3V) CS+, CS-, and V5 to GND ........................................-0.3V to +6V OUT Short Circuited to GND Duration (at VIN = +16V) ........................................................60 minutes Maximum Current into Any Pin (except IN and OUT) .........±20mA Continuous Power Dissipation (TA = +70°C) 16-Pin TQFN 5mm x 5mm (derate 33.3mW/°C above +70°C) ...........................2666.7mW Junction to Case Thermal Resistance (θJC) (Note 1) ........2°C/W Junction to Ambient Thermal Resistance (θJA) (Note 1) ....30°C/W Operating Junction Temperature Range ...........-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Package thermal resistances obtained using the method described in JEDEC specification JESD51-7, using a four-layer 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 = VEN = +12V, CV5 = 0.1µF to GND, IV5 = 0, CS- = GND, connect RSENSE = 0.58Ω between CS+ and CS-. TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 2 and 3) PARAMETER Supply Voltage Range Ground Current Shutdown Supply Current Guaranteed Output Current SYMBOL (Note 2) IG ILOAD = 350mA ISHDN IOUT Output Current Accuracy Dropout Voltage (Note 4) CONDITIONS VIN ΔVDO Output Current Slew Rate Short-Circuit Current MIN VEN ≤ 0.6V RSENSE = 0.55Ω TYP MAX UNITS 40.0 V 1.28 3 mA 35 70 6.5 350 µA mA 35mA < IOUT < 350mA ±3.5 IOUT = 350mA (current pulsed), 12V < VIN < 40V 0.55 1.2 V IOUT = 350mA (current pulsed), 6.5V < VIN < 40V 0.55 1.5 V Current rising 7.8 Current falling 7.8 VIN = 12V, VCS+ = 0V % mA/µs 400 500 650 mA -1.0 -0.2 µA LOGIC INPUT EN Input Current IEN -2.5 EN Input Voltage High VIH 2.8 EN Input Voltage Low VIL Turn-On Time tON V 0.6 V 110 350 µs 193 200 207 mV 2.7 7.0 µA -50 -17.2 VEN rising edge to 90% of OUT CURRENT SENSE Regulated RSENSE Voltage VSENSE VSENSE = VCS+ - VCS- Input Current (CS+) VCS+ = 220mV Input Current (CS-) VCS+ = 220mV 2 _______________________________________________________________________________________ µA High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver (VIN = VEN = +12V, CV5 = 0.1µF to GND, IV5 = 0, CS- = GND, connect RSENSE = 0.58Ω between CS+ and CS-. TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 2 and 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS THERMAL OVERLOAD Thermal-Shutdown Temperature +159 °C 24 °C Thermal-Shutdown Hysteresis +5V REGULATOR Output Voltage VV5 Output Voltage Load Regulation ΔV5 4.85 V5 Short-Circuit Current 5.00 5.20 V 0 < ILOAD < 4mA (Note 5) 12 20 mV/mA V5 = 0V (Note 6) 15 mA Note 2: Resistors were added from OUT to CS+ to aid with the power dissipation during testing. Note 3: All devices 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design. Note 4: Dropout is measured as follows: Connect RO = 27Ω from OUT to CS+. Connect RSENSE = 0.58Ω from CS+ to CS-. Set VIN = +12V (record VOUT as VOUT1). Reduce VIN until VOUT = 0.97 x VOUT1 (record as VIN2 and VOUT2). ΔVDO = VIN2 - VOUT2. Note 5: Current regulation varies with V5 load (see the Typical Operating Characteristics). Note 6: Thermal shutdown does not function if the output of the 5V reference is shorted to ground. Typical Operating Characteristics (VIN = VEN = +12V, TA = +25°C, unless otherwise noted.) OUTPUT CURRENT vs. TEMPERATURE 300 250 ILOAD = 200mA 200 150 ILOAD = 100mA 100 50 ILOAD = 35mA 0 0.206 0.204 0.202 0.200 MAX16835 toc03 400 350 OUTPUT CURRENT (mA) 350 0.208 OUTPUT CURRENT vs. INPUT VOLTAGE MAX16835 toc02 ILOAD = 350mA (VCS+ - VCS-) (V) OUTPUT CURRENT (mA) 400 MAX16835 toc01 450 (VCS+ - VCS-) vs. OUTPUT CURRENT 300 250 200 150 100 50 0.198 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 20 50 80 110 140 170 200 230 260 290 320 350 TEMPERATURE (°C) OUTPUT CURRENT (mA) 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) _______________________________________________________________________________________ 3 MAX16835 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VIN = VEN = +12V, TA = +25°C, unless otherwise noted.) ILOAD = 350mA 0.6 0.5 0.4 0.3 90 VIN = 40V 80 70 VIN = 20V 60 50 40 30 20 0.2 VIN = 12V 5.1 IV5 = 1mA NO LOAD 5.0 4.9 VIN = 6.5V 10 0.1 5.2 +5V REGULATOR OUTPUT (V) DROPOUT VOLTAGE (V) 0.8 100 MAX16835 toc05 0.9 SHUTDOWN CURRENT (μA) MAX16835 toc04 1.0 0.7 +5V REGULATOR OUTPUT vs. TEMPERATURE SHUTDOWN CURRENT vs. TEMPERATURE MAX16835 toc06 DROPOUT VOLTAGE vs. TEMPERATURE IV5 = 5mA 0 0 4.8 -40 -25 -10 5 20 35 50 65 80 95 110 125 -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) TEMPERATURE (°C) (VCS+ - VCS-) vs. IV5 +5V REGULATOR OUTPUT vs. VIN 0.202 0.200 ILOAD = 350mA 0.198 MAX16835 toc09 MAX16835 toc08 0.204 200Hz DIMMED OPERATION 5.2 +5V REGULATOR OUTPUT (V) MAX16835 toc07 0.206 (VCS+ - VCS-) (V) MAX16835 High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver IV5 = 5mA NO LOAD 0V 5.0 ILOAD 200mA/div 4.9 0 IV5 = 5mA 0.196 ILOAD = 350mA, VIN = VEN, VIN PULSED AT 200Hz (50% DUTY CYCLE) 4.8 0 1 2 3 4 5 5 IV5 (mA) 10 15 20 25 30 35 40 1ms/div VIN (V) 200Hz DIMMED OPERATION EXPANDED 200Hz DIMMED OPERATION EXPANDED MAX16835 toc10 MAX16835 toc11 0V ILOAD 200mA/div 200Hz DIMMED OPERATION MAX16835 toc12 VIN 5V/div VIN 5V/div ILOAD = 350mA VIN = VEN VIN PULSED AT 200Hz (50% DUTY CYCLE) VIN 5V/div 5.1 ILOAD = 350mA VIN = VEN VIN PULSED AT 200Hz (50% DUTY CYCLE) 0 EN 10V/div 0V 0V ILED 200mA/div ILED 200mA/div 0 0 ILOAD = 350mA, VIN = 12V, EN PULSED AT 200Hz (50% DUTY CYCLE) 20μs/div 4 4μs/div 1ms/div _______________________________________________________________________________________ High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver PIN NAME 1, 16 OUT FUNCTION 2, 3 IN 4–8, 13, 14 N.C. No Connection. Not internally connected. 9 CS+ Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS+ and CS- to program the output current level. 10 CS- Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS- and CS+ to program the output current level. 11 V5 +5V Regulated Output. Connect a 0.1µF capacitor from V5 to GND. 12 GND 15 EN Enable Input. Drive EN high to enable the output. — EP Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only ground connection. Current-Regulated Output. Connect pin 1 to pin 16. Positive Input Supply. Bypass IN with a 0.1µF (min) capacitor to GND. Connect pin 2 to pin 3. Ground Functional Diagram V5 IN REGULATOR IN EN ENABLE REFERENCE GENERATOR I-REG OUT DIFFERENTIAL SENSE AMPLIFIER MAX16835 CS+ CS- THERMAL SHUTDOWN Detailed Description The MAX16835 is a high-current regulator capable of providing up to a total of 350mA of current to one or more strings of high-brightness LEDs. A wide operating input voltage range of +6.5V to +40V makes the MAX16835 ideal for automotive applications. A +5V regulated output provides up to 4mA of current to power external circuitry. In addition, the MAX16835 features thermal and output short-circuit protection. The wide operating voltage range helps protect the MAX16835 against large transients such as those found in load-dump situations up to 40V. The MAX16835 uses a feedback loop to control the output current. The differential voltage across the sense resistor is compared to a fixed reference voltage, and the error is amplified to serve as the drive to the internal _______________________________________________________________________________________ 5 MAX16835 Pin Description MAX16835 High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver power series pass device (see the Functional Diagram). The regulation point is factory set at (VCS+ - VCS-) = 200mV ±3.5%. The regulated current is user defined by the value of RSENSE. The MAX16835 is a current controller internally optimized for driving the impedance range expected from one or more HB LEDs. connected across RSENSE provides ground-loop immunity and low-frequency noise rejection. The LED current is given by the equation below: ILED = VSENSE/RSENSE +5V Regulator VIN(MIN) ≥ VSENSE(MAX) + VFT(MAX + ΔVDO(MAX) where VFT(MAX) is the total forward voltage of all seriesconnected LEDs. The minimum operating voltage of the device is +6.5V. The device operates below +6.5V; However, the output current may not meet the full regulation specification. The MAX16835 includes a fixed +5V output regulator that delivers up to 4mA of load current for low-power applications throughout the +6.5V to +40V input voltage range. Connect a 0.1µF compensation capacitor from V5 to ground. Shorting V5 to ground disables the thermal shutdown. When EN is low, V5 is off. Input Voltage Considerations For proper operation, the minimum input voltage must always be: Low-Frequency PWM at the Output Thermal Protection The MAX16835 enters a thermal-shutdown mode in the event of overheating. This typically occurs in overload or output short-circuit conditions. When the junction temperature exceeds TJ = +159°C (typ), the internal thermal-protection circuitry turns off the series pass device. The MAX16835 recovers from thermal-shutdown mode once the junction temperature drops by 24°C (typ). The part therefore protects itself by thermally cycling in the event of a short-circuit or overload condition. Shorting V5 to ground disables the thermal shutdown. Applications Information Programming the LED Current The MAX16835 uses a sense resistor across CS+ and CS- to set the LED current. The differential sense amplifier The MAX16835 provides pulsed or chopped current dimming. Generally, HB LEDs are binned to match at their full-rated current; however, LEDs from the same bin exhibit poor matching at currents other than fullrated current. To achieve uniformity, HB LED manufacturers recommend PWM pulsing of the LED current at their full-rated value. There are two methods for producing a PWM output. One method is by pulsing the enable input (EN) while having a constant voltage at IN. The other method is to connect EN to IN and pulse both EN and IN. Both methods generate a regulated-amplitude PWM current (variable duty cycle) that can provide control over the LED brightness (see Figures 1 and 2). VEN 1 OUT 2 IN 3 IN 4 N.C. 16 15 14 13 16 15 14 13 OUT EN N.C. N.C. OUT EN N.C. N.C. ILED GND 12 D1 VIN VIN V5 11 C1 C2 MAX16835 CS- 10 RSENSE CS+ 9 OUT 2 IN 3 IN 4 N.C. ILED GND 12 D1 V5 11 C1 C2 MAX16835 CS- 10 CS+ 9 N.C. N.C. N.C. N.C. N.C. N.C. N.C. N.C. 5 6 7 8 5 6 7 8 Figure 1. Pulse Application with VIN at a Constant Voltage 6 1 Figure 2. Pulse Application with EN Connected to VIN _______________________________________________________________________________________ RSENSE High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver Chip Information PROCESS: BiCMOS 1 OUT 2 IN 3 IN 4 N.C. 16 15 14 13 OUT EN N.C. N.C. Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. GND 12 D1 VIN V5 11 C1 C2 MAX16835 CS- 10 RSENSE PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16 TQFN T1655-3 21-0140 CS+ 9 N.C. N.C. N.C. N.C. 5 6 7 8 _______________________________________________________________________________________ 7 MAX16835 Typical Operating Circuit MAX16835 High-Voltage, 350mA, Adjustable Linear High-Brightness LED Driver Revision History REVISION NUMBER REVISION DATE 0 2/08 Initial release 5/08 Updated Ordering Information, Electrical Characteristics, and Package Information. 1 DESCRIPTION PAGES CHANGED — 1, 2, 8, 9 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2008 Maxim Integrated Products Quijano is a registered trademark of Maxim Integrated Products, Inc.