MAX8743 19-3318 Rev 1 8/05 Dual, High-Efficiency, Step-Down Controller with High Impedance in Shutdown General Description Features The MAX8743 is a dual pulse-width modulation (PWM) Ultra-High Efficiency controller configured for step-down (buck) topologies Accurate Current-Limit Option that provides the high efficiency, excellent transient Quick-PWM with 100ns Load-Step Response response, and high DC output accuracy necessary for stepping down high-voltage batteries to generate low- 1% V Accuracy over Line and Load OUT voltage chipset and RAM power supplies in notebook High Output Impedance in Shutdown computers. The CS inputs can be used with low-side sense resistors to provide accurate current limits or can Dual Mode Fixed 1.8V/1.5V/Adj or 2.5V/Adj Outputs be connected to LX , using low-side MOSFETs as cur- Adjustable 1V to 5.5V Output Range rent-sense elements. High output impedance in shut- 2V to 28V Battery Input Range down eliminates negative output voltages, saving the cost of a Schottky diode at the output. 200kHz/300kHz/420kHz/540kHz Nominal Switching Frequency The on-demand PWM controllers are free running, con- stant on-time with input feed-forward. This configuration Adjustable Overvoltage Protection provides ultra-fast transient response, wide input-output 1.7ms Digital Soft-Start differential range, low supply current, and tight load-reg- ulation characteristics. The MAX8743 is simple and easy Drives Large Synchronous-Rectifier FETs to compensate. Power-Good Window Comparator Single-stage buck conversion allows the MAX8743 to 2V 1% Reference Output directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion Ordering Information (stepping down the 5V system supply instead of the bat- PART TEMP RANGE PIN-PACKAGE tery at a higher switching frequency) allows the minimum possible physical size. MAX8743EEI -40C to +85C 28 QSOP MAX8743EEI+ -40C to +85C 28 QSOP The MAX8743 is intended for generating chipset, DRAM, CPU I/O, or other low-voltage supplies down to 1V. The +Denotes lead-free package. MAX8743 is available in 28-pin QSOP and 36-pin thin Ordering Information continued at end of data sheet. QFN packages. Minimal Operating Circuit Applications 5V INPUT BATTERY Notebook Computers 4.5V TO 28V V V+ DD CPU Core Supplies V CC UVP MAX8743EEI Chipset/RAM Supplies as Low as 1V ILIM1 OVP ILIM2 1.8V and 2.5V I/O Supplies ON1 ON2 BST1 BST2 OUTPUT1 OUTPUT2 DH1 DH2 1.8V 2.5V LX1 LX2 DL1 DL2 CS2 TON CS1 OUT1 PGOOD OUT2 REF SKIP FB2 FB1 Pin Configurations appear at end of data sheet. GND Quick-PWM and Dual Mode are trademarks 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.Dual, High-Efficiency, Step-Down Controller with High Impedance in Shutdown ABSOLUTE MAXIMUM RATINGS (Note 1) V+ to AGND..............................................................-0.3 to +30V LX to BST ..............................................................-6V to +0.3V V to AGND............................................................-0.3V to +6V DH2 to LX2 ..............................................-0.3V to (V + 0.3V) CC BST2 V to PGND............................................................-0.3V to +6V REF Short Circuit to GND...........................................Continuous DD AGND to PGND.....................................................-0.3V to +0.3V Continuous Power Dissipation (T = +70C) A PGOOD, OUT to AGND..........................................-0.3V to +6V 28-Pin QSOP (derate 10.8mW/C above +70C)........860mW OVP, UVP, ILIM , FB , REF, 36-Pin 6mm 6mm Thin QFN SKIP, TON, ON to AGND......................-0.3V to (V + 0.3V) (derate 26.3mW/C above +70C).............................2105mW CC DL to PGND..............................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C DD BST to AGND........................................................-0.3V to +36V Junction Temperature......................................................+150C CS to AGND.............................................................-6V to +30V Storage Temperature Range .............................-65C to +150C DH1 to LX1 ..............................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C BST1 Note 1: For the MAX8743EEI, AGND and PGND refer to a single pin designated GND. 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 = V = 5V, SKIP = AGND, V+ = 15V, T = 0C to +85C, typical values are at +25C, unless otherwise DD CC A noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS PWM CONTROLLERS V+ Battery voltage, V+ 2 28 Input Voltage Range V V /V V , V 4.5 5.5 CC DD CC DD FB1 to AGND 1.782 1.8 1.818 V+ = 2V to 28V, I LOAD = 0 to 8A, SKIP = V , FB1 to V 1.485 1.5 1.515 CC CC +25C to +85C FB1 to OUT1 0.99 1 1.01 DC Output Voltage OUT1 V V OUT1 (Note 2) FB1 to AGND 1.773 1.8 1.827 V+ = 2V to 28V, I LOAD = 0 to 8A, SKIP = V , FB1 to V 1.477 1.5 1.523 CC CC 0C to +85C FB1 to OUT1 0.985 1 1.015 V+ = 4.5V to 28V, FB2 to AGND 2.475 2.5 2.525 I = 0 to 4A, LOAD SKIP = V , CC FB2 to OUT2 0.99 1 1.01 +25C to +85C DC Output Voltage OUT2 V V OUT2 (Note 2) V+ = 4.5V to 28V, FB2 to AGND 2.463 2.5 2.537 I = 0 to 4A, LOAD SKIP = V , CC FB2 to OUT2 0.985 1 1.015 0C to +85C Output Voltage Adjust Range OUT1, OUT2 1 5.5 V Dual-Mode Threshold, Low OVP, FB 0.05 0.1 0.15 V V - V - CC CC OVP, ILIM 1.5 0.4 Dual-Mode Threshold, High V FB1 1.9 2.0 2.1 R V = 1.5V 75 OUT1 OUT1 OUT Input Resistance k R V = 2.5V 100 OUT2 OUT2 FB Input-Bias Current I -0.1 +0.1 A FB Soft-Start Ramp Time Zero to full ILIM 1700 s 2 MAX8743