MAX1684/MAX1685 19-1454 Rev 2 7/01 Low-Noise, 14V Input, 1A, PWM Step-Down Converters General Description Features The MAX1684/MAX1685 are high-efficiency, internal- Up to 96% Efficiency switch, pulse-width modulation (PWM) step-down switch- 1A Guaranteed Output Current ing regulators intended to power cellular phones, communicating PDAs, and handy-terminals. These 100% Duty Cycle in Dropout devices deliver a guaranteed 1A output current from two 2.7V to 14V Input Range (15V Absolute Max) lithium-ion (Li+) batteries. Their wide-input voltage range 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 0.24 P-Channel On-Resistance higher voltages that occur when the battery is removed. The output voltage is preset to 3.3V or can be externally Synchronizable Switching Frequency adjusted from 1.25V to V . IN Fixed-Frequency PWM Operation The low on-resistance power switch and built-in synchro- 300kHz (MAX1684) nous rectifier provide high efficiencies of up to 96%. 600kHz (MAX1685) There are four modes of operation: fixed-frequency, nor- mal, low-power, and shutdown. The fixed-frequency 150A Normal-Mode Quiescent Current PWM mode of operation offers excellent noise character- 25A Low-Power Mode Quiescent Current istics. The normal mode maintains high efficiency at all loads. The low-power mode is used to conserve power in 2A Shutdown Current standby or when full load is not required. The shutdown Dual Mode Fixed 3.3V (1%) Output or mode is used to power down the device for minimal cur- Adjustable Output (1.25V to V ) rent draw. IN 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 PART TEMP RANGE PIN-PACKAGE output, and a 1% accurate reference. MAX1684EEE -40C to +85C 16 QSOP Both devices are available in a space-saving 16-QSOP MAX1685EEE -40C to +85C 16 QSOP package. An evaluation kit is also available to help speed designs. For a similar device in a 10-pin MAX Typical Operating Circuit package with lower input voltage requirements (5.5V max), refer to the MAX1692 data sheet. Applications OUTPUT INPUT 2.7V TO 14V 3.3V AT 1A Cellular Phones IN LX + + Two-Way Radios and Walkie-Talkies AIN MAX1684 Computer Peripherals MAX1685 SHDN GND Personal Communicators CVH PDAs and Handy-Terminals 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 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 AVAILABLELow-Noise, 14V Input, 1A, PWM Step-Down Converters ABSOLUTE MAXIMUM RATINGS AIN to AGND ............................................................-0.3 to +15V CVL Current .......................................................-1mA to +10mA IN to PGND ................................................-0.3V to (V + 0.3V) LX Peak Current (Internally Limited) .....................................2.3A AIN LX to PGND .................................................-0.5V to (V + 0.3V) Continuous Power Dissipation (T = +70C) IN A PGND to AGND ..................................................................0.3V 16-Pin QSOP (derate 8.3mW/C above +70C)............667mW SHDN to AGND .........................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C AIN ILIM/SS, FB, CC, BOOT, REF to AGND ....-0.3V to (V + 0.3V) Junction Temperature......................................................+150C CVL CVH to IN..................................................................-6V to +0.3V Storage Temperature Range .............................-65C to +150C CVL, STBY, SYNC/PWM to AGND............................-0.3V to +6V Lead Temperature (soldering, 10s) .................................+300C Reference Current ..............................................................1mA 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 (V = V = 6V, STBY = SYNC/PWM = CVL, V = V , FB = AGND, circuit of Figure 1, T = 0C to +85C, unless otherwise IN SHDN BOOT OUT A noted. Typical values are at T = +25C.) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage Range 2.7 14 V Feedback Voltage V V = V , I = 0 to 1A 1.238 1.251 1.264 V FB FB OUT LOAD Output Voltage (3.3V Mode) V FB = AGND, I = 0 to 1A 3.296 3.333 3.368 V OUT LOAD Output Load Regulation V = V , I = 0 to 1A 0.01 % FB OUT LOAD Output Current Capability V = 5V to 14V 1 A IN Output Adjust Range BOOT = AGND (Note 1) V V V REF IN FB Input Current I V = 1.4V -50 50 nA FB FB V = 6V 0.24 0.5 IN High-side switch, On-Resistance, P-Channel I = 1A LX V = 2.7V 0.34 0.8 IN On-Resistance, N-Channel Low-side switch, V = 2.7V, I = 200mA 38 IN LX Current Limit in PWM Mode I 1.2 1.75 2.3 A LIM Pulse-Skipping Current Threshold SYNC/PWM = low 285 380 475 mA Current Limit in Low-Power I STBY = low 285 380 475 mA LIMLP Mode Current Limit, N-Channel SYNC/PWM = high 0.15 0.4 0.9 A MAX1684 -10 50 100 Zero Crossing Threshold SYNC/PWM = low mA MAX1685 20 80 130 PWM mode, MAX1684 13 33 SYNC/PWM = high, V = 3.3V BOOT MAX1685 25 65 (Note 2) Quiescent Power Consumption mW Normal mode, SYNC/PWM = low, 0.9 2 V = 3.3V (Note 2) BOOT Low-power mode, STBY = low, 0.14 0.27 V = 3.3V (Note 2) BOOT 2 MAX1684/MAX1685