MAX1984/MAX1985/MAX1986 19-2761 Rev 0 1/03 Ultra-High-Efficiency White LED Drivers General Description Features The MAX1984/MAX1985/MAX1986 are white light-emit- Synchronous Step-Up Regulator ting diode (LED) drivers that use individual regulators to Achieves >95% Efficiency control the current of up to eight LEDs. A high-efficiency Internal Switch and Synchronous Rectifier step-up regulator generates just enough voltage to keep Eliminates External MOSFETs and Diodes all the current regulators in regulation. A versatile dim- 1MHz Fixed Frequency Minimizes Component ming interface accommodates analog, digitally adjusted Sizes pulse-width modulation (DPWM), or parallel control. Up to 90% Total LED Efficiency The individual current regulators allow good current Accurate LED Current Matching (8% max) matching between LEDs. Open or shorted LEDs cannot Adjustable Maximum LED Current affect the performance of other LEDs. Multimode Dimming Control The step-up regulator achieves high efficiency by using Digital Pulse-Width Modulation Control synchronous rectification. The internal N-channel switch 2-Bit Parallel Control and P-channel synchronous rectifier eliminate the need 3-Bit Parallel Control for external MOSFETs and diodes. The 1MHz switching Analog Control frequency allows the use of low-profile inductors and ceramic capacitors. Selectively Enable LEDs The brightness can be easily adjusted using a multi- Open-LED Detection mode dimming interface, which allows brightness control Unique 0.5mA LED Test Mode through a DPWM signal, a 2- or 3-bit parallel control 2.7V to 5.5V Input Supply Range interface, or an analog signal. The DPWM signal can be connected directly to the control pin without the need for Small 4mm x 4mm 20-Pin Thin QFN Package an external RC filter if its frequency is 10kHz or above. The MAX1984 drives up to eight LEDs, the MAX1985 drives up to six LEDs, and the MAX1986 drives up to Ordering Information four LEDs. Each device has an LED select pin (SEL) that allows one subset, the other subset, or all LEDs to NO. OF PART TEMP RANGE PIN-PACKAGE be illuminated. All three devices are available in a LEDs 4mm 4mm thin QFN package. MAX1984ETP -40C to +85C 20 Thin QFN 8 Applications MAX1985ETP -40C to +85C 20 Thin QFN 6 PDAs and Hand-Held PCs MAX1986ETE -40C to +85C 16 Thin QFN 4 Cellular Phones Digital Cameras Pin Configurations TOP VIEW 20 19 18 17 16 20 19 18 17 16 16 15 14 13 OUT 1 15 BITB OUT 1 15 BITB OUT 1 12 BITA LX 2 14 REF LX 2 14 REF LX 2 11 BITB GND 3 13 SETI GND 3 13 SETI MAX1984 MAX1985 MAX1986 GND 3 10 REF LD1 4 12 LD8 N.C. 4 12 N.C. LD1 4 9 SETI LD2 5 11 LD7 LD1 5 11 LD6 6 7 8 9 10 6 7 8 9 10 5 6 7 8 4mm x 4mm 4mm x 4mm 4mm x 4mm THIN QFN THIN QFN THIN QFN Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE LD3 SEL LD4 MODE LDG IN LD5 BITC LD6 BITA LD2 SEL LD3 MODE LDG IN LD4 BITC LD5 BITA LD2 SEL LDG MODE LD3 IN LD4 BITCUltra-High-Efficiency White LED Drivers ABSOLUTE MAXIMUM RATINGS OUT, IN, BITA, BITB, BITC, LD1, LD2, LD3, LD4, Operating Temperature Range ...........................-40C to +85C LD5, LD6, LD7, LD8 to GND ................................-0.3V to +6V Junction Temperature......................................................+150C LDG to GND........................................................................0.3V Storage Temperature Range .............................-65C to +150C LX to GND ................................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C OUT SETI, REF, MODE, SEL to GND...................-0.3V to (V + 0.3V) IN Continuous Power Dissipation (T = +70C) A 16-Pin Thin QFN (derate 16.9mW/C above +70C) ...1349mW 20-Pin Thin QFN (derate 16.9mW/C above +70C) ...1349mW 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 (Circuit of Figure 1 V = 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, C = 4.7F, C = 0.22F, T = 0C to +85C, IN OUT REF A unless otherwise noted. Typical values are at T = +25C.) A PARAMETER CONDITIONS MIN TYP MAX UNITS IN Supply Range 2.7 5.5 V IN Undervoltage Lockout Threshold 50mV typical hysteresis 2.2 2.4 2.6 V IN Quiescent Current BITA = BITB = BITC = IN, LD1 to LD8 = GND 400 600 A IN Shutdown Current BITA = BITB = BITC = GND 0.1 1 A REF Output Voltage I = 0 1.230 1.250 1.270 V REF REF Line Regulation 2.7V < V < 5.5V 0.2 5 mV IN REF Load Regulation -1A < I < +50A 5 15 mV REF Oscillator Frequency 0.8 1 1.2 MHz Oscillator Maximum Duty Cycle 85 % OUT Overvoltage Protection (OVP) V to V = 50mV, OUT rising, 100mV typical LD1 LD8 5.1 5.3 5.5 V Threshold hysteresis INTERNAL MOSFET SWITCHES N-Channel MOSFET On-Resistance I = 200mA 0.4 0.8 LX N-Channel MOSFET Leakage Current V = 5.5V, BITA = BITB = BITC = GND 0.1 1 A LX P-Channel MOSFET On-Resistance I = 200mA 0.5 1 LX P-Channel MOSFET Leakage Current LX = GND, V = 5.5V, BITA = BITB = BITC = GND 0.1 1 A OUT MAX1984 0.50 0.65 0.81 N-Channel MOSFET Current Limit MAX1985 0.40 0.52 0.65 A MAX1986 0.30 0.39 0.52 CONTROL INPUTS BITA, BITB, BITC Input Logic Low 2.7V < V < 5.5V 0.4 V IN Level BITA, BITB, BITC Input Logic High 2.7V < V < 5.5V 1.6 V IN Level MODE Input Logic Low Level 2.7V < V < 5.5V 0.4 V IN MODE Input Logic High Level 2.7V < V < 5.5V V - 0.4 V IN IN MODE, BITA, BITB, BITC Input Bias 2.7V < V < 5.5V 0.01 1 A IN Current 2 MAX1984/MAX1985/MAX1986