19-1454; Rev 2; 7/01 EVALUATION KITAVAILABLELow-Noise, 14V Input, 1A, PWMStep-Down ConvertersMAX1684/MAX1685General DescriptionFeatures The MAX1684/MAX1685 are high-efficiency, internal- ♦ Up to 96% Efficiency switch, pulse-width modulation (PWM) step-down switch- ing regulators intended to power cellular phones, ♦ 1A Guaranteed Output Current communicating PDAs, and handy-terminals. These ♦ 100% Duty Cycle in Dropout devices deliver a guaranteed 1A output current from two lithium-ion (Li+) batteries. Their wide-input voltage range ♦ 2.7V to 14V Input Range (15V Absolute Max) of 2.7V to 14V gives design flexibility and allows batteries ♦ ±1% Accurate Reference Output to charge from a wall cube, since the ICs operate at the higher voltages that occur when the battery is removed. ♦ 0.24 Ω P-Channel On-Resistance The output voltage is preset to 3.3V or can be externally ♦ Synchronizable Switching Frequency adjusted from 1.25V to VIN. ♦ Fixed-Frequency PWM Operation The low on-resistance power switch and built-in synchro- nous rectifier provide high efficiencies of up to 96%. 300kHz (MAX1684) There are four modes of operation: fixed-frequency, nor- 600kHz (MAX1685) mal, low-power, and shutdown. The fixed-frequency ♦ 150µA Normal-Mode Quiescent Current PWM mode of operation offers excellent noise character- istics. The normal mode maintains high efficiency at all ♦ 25µA Low-Power Mode Quiescent Current loads. The low-power mode is used to conserve power in ♦ 2µA Shutdown Current standby or when full load is not required. The shutdown mode is used to power down the device for minimal cur- ♦ Dual Mode™ Fixed 3.3V (±1%) Output or rent draw. Adjustable Output (1.25V to VIN) The MAX1684 runs at 300kHz for applications that ♦ Small 16-QSOP Package require highest efficiency. The MAX1685 runs at ♦ Auxiliary Output (CVL): 3V/5mA 600kHz to allow the use of smaller external compo- nents. These devices can also be synchronized to an Ordering Information external clock. Other features include a 100% duty cycle for low-dropout applications, an auxiliary 3V/5mA PARTTEMP RANGEPIN-PACKAGE output, and a 1% accurate reference. MAX1684 EEE -40°C to +85°C 16 QSOP Both devices are available in a space-saving 16-QSOP MAX1685 EEE -40°C to +85°C 16 QSOP package. An evaluation kit is also available to help speed designs. For a similar device in a 10-pin µMAX package with lower input voltage requirements (5.5V Typical Operating Circuit max), refer to the MAX1692 data sheet. Applications INPUT OUTPUT Cellular Phones 2.7V TO 14V 3.3V AT 1A IN LX + + Two-Way Radios and Walkie-Talkies AIN MAX1684 Computer Peripherals SHDN MAX1685 Personal Communicators GND PDAs and Handy-Terminals CVH CVL BOOT STBY SYNC/PWM Pin Configuration appears at end of data sheet. FB CC REF Dual Mode is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products1For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.