MAX1761 19-1835 Rev 0 10/00 Small, Dual, High-Efficiency Buck Controller for Notebooks General Description Features The MAX1761 dual pulse-width-modulation (PWM), Free-Running On-Demand PWM step-down controller provides high efficiency, excellent Selectable Light-Load Pulse-Skipping Operation transient response, and high DC output accuracy in an extremely compact circuit topology. These features are 1% Total DC Error in Forced-PWM Mode essential for stepping down high-voltage batteries to 5V to 20V Input Range generate low-voltage CPU core, I/O, and chipset RAM supplies in PC board area critical applications, such as Flexible Output Voltages notebook computers and smart phones. OUT1: Dual Mode Fixed 2.5V or 1V to 5.5V Maxims proprietary Quick-PWM quick-response, Adjustable constant-on-time PWM control scheme handles wide OUT2: Dual Mode Fixed 1.8V or 1V to 5.5V input/output voltage ratios with ease and provides instant-on response to load transients while maintain- Adjustable ing a relatively constant switching frequency. Output Undervoltage Protection The MAX1761 achieves high efficiency at reduced cost Complementary Synchronous Buck by eliminating the current-sense resistor found in tradi- tional current-mode PWMs. Efficiency is further No Current-Sense Resistor enhanced by its ability to drive large synchronous-recti- 4.65V at 25mA Linear Regulator Output fier MOSFETs. The MAX1761 employs a complemen- tary MOSFET output stage, which reduces component 4A V+ Shutdown Supply Current count by eliminating external bootstrap capacitors and 5A VL Shutdown Supply Current diodes. 950A Quiescent Supply Current Single-stage buck conversion allows this device to directly step down high-voltage batteries for the highest Tiny 16-Pin QSOP Package possible efficiency. Alternatively, two-stage conversion (stepping down the +5V system supply instead of the battery) at a higher switching frequency allows the mini- mum possible physical size. The MAX1761 is intended for CPU core, chipset, Ordering Information DRAM, or other low-voltage supplies. The MAX1761 is PART TEMP. RANGE PIN-PACKAGE available in a 16-pin QSOP package. For applications MAX1761EEE -40C to +85C 16 QSOP requiring greater output power, refer to the MAX1715 data sheet. For a single-output version, refer to the MAX1762/MAX1791 data sheet. Pin Configuration Applications Notebooks and PDAs TOP VIEW Digital Cameras FB1 1 16 DH1 Handy-Terminals OUT1 2 15 CS1 Smart Phones REF 3 14 DL1 1.8V/2.5V Logic and I/O Supplies ON2 4 MAX1761 13 VL V+ 5 12 GND ON1 6 11 DL2 OUT2 7 10 CS2 FB2 8 9 DH2 Quick-PWM and Dual Mode are trademarks of Maxim Integrated Products. QSOP Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLESmall, Dual, High-Efficiency Buck Controller for Notebooks ABSOLUTE MAXIMUM RATINGS V+ to GND..............................................................-0.3V to +22V Continuous Power Dissipation VL to GND ................................................................-0.3V to +6V 16-Pin QSOP (derate 8.3mW/C above +70C) .......667mW VL to V+ .............................................................................+0.3V Operating Temperature Range ...........................-40C to +85C OUT , ON2 to GND..................................................-0.3V to +6V Junction Temperature......................................................+150C ON1, DH to GND ........................................-0.3V to (V+ + 0.3V) Storage Temperature.........................................-65C to +150C FB , REF, DL to GND.................................-0.3V to (VL + 0.3V) Lead Temperature (soldering, 10s) .................................+300C CS to GND.....................................................-2V to (V+ + 0.3V) REF Short Circuit to GND...........................................Continuous 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+ = 15V, C = 4.7F, C = 0.1F, VL not externally driven unless otherwise noted, T = 0C to +85C, unless VL REF A otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS PWM CONTROLLERS Input Voltage Range V+ (Note 2) 4.5 20 V FB = OUT 0.99 1 1.01 V+ = 4.5V to 20V, DC Output Voltage Accuracy V VL = 4.75V to 5.25V, FB1 = GND 2.475 2.5 2.525 V OUT (Note 3) ON2 = VL FB2 = GND 1.782 1.8 1.818 Output Voltage Adjust Range 1 5.5 V OUT Input Resistance 80 160 300 k FB Input Bias Current V = 1V, VL = 5V -0.1 0.1 A FB CS Input Bias Current V = 0, VL = 5V -1 1 A CS Soft-Start Ramp Time Zero to full ILIM 1700 s OUT1 661 735 809 V+ = 10V, V = 2.5V, OUT1 On-Time (Note 4) t ns ON V = 1.8V OUT2 OUT2 648 720 792 Minimum Off-Time (Note 4) t 400 500 ns OFF BIAS AND REFERENCE FB1 = FB2 = GND, VL = 5V, V and OUT1 IL 0.60 1.20 mA V forced above regulation point OUT2 Quiescent Supply Current FB1 = FB2 = GND, V VL undriven 0.95 1.70 OUT1 I+ and V forced mA OUT2 VL = 5V 0.38 0.65 above regulation point IL VL = 5V, ON1 = ON2 = GND 5 10 A Shutdown Supply Current I+ VL = 0, 5V 4 10 A VL Output Voltage VL I = 0 to 25mA, V+ = 5V to 20V 4.5 4.65 4.75 V LOAD Reference Voltage V V+ = 5V to 20V, no load 1.98 2 2.02 V REF Reference Load Regulation I I = 0 to 50A 8 mV REF REF REF Sink Current REF in regulation 10 A Falling edge 1.6 REF Fault Lockout Voltage V Rising edge 1.94 2 MAX1761