MAX1677 19-1403 Rev 1 3/01 Compact, High-Efficiency, Dual-Output Step-Up and LCD Bias DC-DC Converter General Description Features The MAX1677 is a compact, high-efficiency, dual-out- No External FETs Required put boost converter for portable devices needing two Main Output regulated supplies, typically for logic and liquid crystal Up to 350mA for Logic Supply displays (LCDs). Operation with inputs as low as 0.7V allows the MAX1677 to accept 1, 2, or 3-cell alkaline, Fixed 3.3V or Adjustable (2.5V to 5.5V) NiCd, or NiMH batteries as well as 1-cell lithium-ion bat- Synchronous Rectification for High Efficiency teries. The device requires no external FETs and can (up to 95%) maintain regulation while consuming only 20A, making 300kHz (200kHz to 400kHz Synchronizable) it ideal for hand-held pen-input and PDA devices oper- Fixed-Frequency PWM Operation ating with low-current sleep states. Secondary Output The MAX1677s primary regulator supplies up to Up to +28V or -28V for LCD Bias 350mA at either a factory-preset 3.3V or an adjustable Programmable Current Limit 2.5V to 5.5V output. On-chip synchronous rectification provides efficiencies up to 95%. 300kHz (or externally 0.7V to 5.5V Input Voltage Range clocked) pulse-width-modulation (PWM) operation is 20A Quiescent Current particularly suitable for applications needing low noise, such as those with wireless features. The primary con- 1A Shutdown Current verter also features pin-selectable pulse-frequency- Low-Battery Comparator modulation (PFM) operation that consumes only 20A. A 1A shutdown state also minimizes battery drain. Small 16-Pin QSOP Package The MAX1677s secondary step-up converter supplies up to +28V or -28V for LCD bias, varactor tuning, or other Ordering Information high-voltage, low-current functions. Other MAX1677 fea- tures include precision reference, logic control inputs for PART TEMP RANGE PIN-PACKAGE both regulators, and an uncommitted comparator for MAX1677EEE -40C to +85C 16 QSOP low-battery detection or a reset function. The MAX1677 is supplied in Maxims compact 16-pin QSOP package, which occupies no more space than a standard SO-8. Typical Operating Circuit Applications PDAs Portable Phones Hand-Held Terminals Portable Instruments V = 0.7V to 5.5V 3.3V MAIN IN (UP TO MAIN ) BOOST OUTPUT OUT LX POUT Pin Configuration MAX1677 28V LCD LCDLX OUT TOP VIEW BOOST OUTPUT LBO OUT 1 16 POUT LBI FB 2 15 LX LCDFB ON LCDON LBI 3 14 PGND OFF REF PWM LBO 4 MAX1677 13 LCDGND CLK/SEL PFM ON FB CLK/SEL 5 12 LCDLX ON OFF LCDON 6 11 ON +VE OUT LCDGND LCDPOL -VE OUT LCDPOL 7 10 LCDFB GND PGND REF 8 9 GND QSOP 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 AVAILABLECompact, High-Efficiency, Dual-Output Step-Up and LCD Bias DC-DC Converter ABSOLUTE MAXIMUM RATINGS OUT, LCDON, ON, POUT, LBI, LBO, Continuous Power Dissipation (T = +70C) A 16-Pin QSOP (derate 8.3mW/C above +70C)...........696mW LX to GND .............................................................-0.3V to +6V CLK/SEL, LCDPOL, REF, LCDFB, Operating Temperature Range ...........................-40C to +85C Junction Temperature......................................................+150C FB to GND .............................................-0.3V to (V + 0.3V) OUT LCDLX to GND .......................................................-0.3V to +30V Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10s) .................................+300C PGND, LCDGND to GND ......................................-0.3V to +0.3V POUT to OUT.........................................................-0.3V to +0.3V Stresses beyond those listed underAbsolute Maximum Rating 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 (V = 3.3V, C = 0.1F, POUT = OUT, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) OUT REF A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Input Voltage Range V (Note 1) 0.7 5.5 V IN Minimum Startup Voltage V T = +25C, I < 1mA 0.9 1.1 V STARTUP A LOAD Reference Voltage V I = 0 1.23 1.25 1.27 V REF REF Reference Load Regulation I = 0 to 50A (Note 2) 2 15 mV REF Reference Line Rejection V = 2.5V to 5.5V 0.2 5 mV OUT Supply Current I No load, current into OUT 20 40 A LCDOFF Main DC On, LCD Off Supply Current All On, I No load, current into OUT 35 60 A PFM Main DC-DC in PFM Mode Supply Current All On, I No load, current into OUT 115 300 A PWM Main DC-DC in PWM Mode Supply Current in Shutdown 0.3 5 A MAIN BOOST DC-DC FB = GND, 0 I 350mA, LX Output Voltage V 3.20 3.30 3.43 V OUT CLK/SEL = OUT (Note 3) FB Regulation Voltage V Adjustable mode, CLK/SEL = OUT (Note 3) 1.225 1.25 1.275 V FB (REG) FB Input Current I V = 1.3V 0.02 50 nA FB FB Output Voltage Adjustment 2.5 5.5 V Range Startup to Normal Mode V 2.1 2.4 V LOCKOUT Transition Voltage (Note 4) Line Regulation I = 150mA, V = 2V to 3V 0.6 % OUT IN CLK/SEL = OUT, V = 2.4V, IN Load Regulation 1% I = 10mA to 200mA LOAD Frequency in Startup Mode f V = 15V 40 300 kHz STARTUP OUT LX Leakage Current I 0.2 5 A LX (LEAK) 2 MAX1677