MAX1953/MAX1954/MAX1957 19-2373 Rev 0 4/02 Low-Cost, High-Frequency, Current-Mode PWM Buck Controller General Description Features The MAX1953/MAX1954/MAX1957 is a family of versa- Low-Cost Current-Mode Controllers tile, economical, synchronous current-mode, pulse-width Fixed-Frequency PWM modulation (PWM) buck controllers. These step-down controllers are targeted for applications where cost and MAX1953 size are critical. 1MHz Switching Frequency The MAX1953 operates at a fixed 1MHz switching fre- Small Component Size, Low Cost quency, thus significantly reducing external component Adjustable Current Limit size and cost. Additionally, excellent transient response MAX1954 is obtained using less output capacitance. The MAX1953 3V to 13.2V Input Voltage operates from low 3V to 5.5V input voltage and can sup- 25A Output Current Capability ply up to 10A of output current. Selectable current limit is provided to tailor to the external MOSFETs on-resistance 93% Efficiency for optimum cost and performance. The output voltage is 300kHz Switching Frequency adjustable from 0.8V to 0.86V . IN MAX1957 With the MAX1954, the drain-voltage range on the high- Tracking 0.4V to 0.86V Output Voltage Range IN side FET is 3V to 13.2V and is independent of the supply Sinking and Sourcing Capability of 3A voltage. It operates at a fixed 300kHz switching frequen- Shutdown Feature cy and can be used to provide up to 25A of output cur- rent with high efficiency. The output voltage is adjustable All N-Channel MOSFET Design for Low Cost from 0.8V to 0.86V . HSD No Current-Sense Resistor Needed The MAX1957 features a tracking output voltage range of 0.4V to 0.86V and is capable of sourcing or sinking Internal Digital Soft-Start IN current for applications such as DDR bus termination Thermal Overload Protection and PowerPC/ASIC/DSP core supplies. The MAX1957 operates from a 3V to 5.5V input voltage and at a fixed Small 10-Pin MAX Package 300kHz switching frequency. Ordering Information The MAX1953/MAX1954/MAX1957 provide a COMP pin that can be pulled low to shut down the converter in PART TEMP RANGE PIN-PACKAGE addition to providing compensation to the error amplifier. MAX1953EUB -40C to +85C 10 MAX An input undervoltage lockout (ULVO) is provided to ensure proper operation under power-sag conditions to MAX1954EUB -40C to +85C 10 MAX prevent the external power MOSFETs from overheating. MAX1957EUB -40C to +85C 10 MAX Internal digital soft-start is included to reduce inrush cur- rent. The MAX1953/MAX1954/MAX1957 are available in Pin Configurations tiny 10-pin MAX packages. TOP VIEW Applications Printers and Scanners ILIM 1 10 BST Graphic Cards and Video Cards COMP 2 9 LX PCs and Servers MAX1953EUB FB 3 8 DH Microprocessor Core Supply GND 4 7 PGND Low-Voltage Distributed Power IN 5 6 DL Telecommunications and Networking MAX Pg PowerPC is a trademark of Motorola, Inc. Pin Configurations continued at end of data sheet. 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-Cost, High-Frequency, Current-Mode PWM Buck Controller ABSOLUTE MAXIMUM RATINGS IN, FB to GND...........................................................-0.3V to +6V Continuous Power Dissipation (T = +70C) A LX to BST..................................................................-6V to +0.3V (derate 5.6mW/C above +70C)..................................444mW BST to GND............................................................-0.3V to +20V Operating Temperature Range ...........................-40C to +85C DH to LX....................................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C BST DL, COMP to GND.......................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +150C IN HSD, ILIM, REFIN to GND ........................................-0.3V to 14V Lead Temperature (soldering, 10s) .................................+300C PGND to GND .......................................................-0.3V to +0.3V I , I ................................................................100mA (RMS) DH DL 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 = 5V, V - V = 5V, T = -40C to +85C, unless otherwise noted. Typical values are at T = +25C.) (Note 1) IN BST LX A A PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Input Voltage Range 3.0 5.5 V HSD Voltage Range MAX1954 only (Note 2) 3.0 13.2 V Quiescent Supply Current V = 1.5V, no switching 1 2 mA FB Standby Supply Current (MAX1953/ MAX1957) V = V = 5.5V, COMP = GND 220 350 A IN BST V = V = 5.5V, V = 13.2V, IN BST HSD Standby Supply Current (MAX1954) 220 350 A COMP = GND Undervoltage Lockout Trip Level Rising and falling V , 3% hysteresis 2.50 2.78 2.95 V IN 0.86 x Output Voltage Adjust Range (V ) 0.8 V OUT V IN ERROR AMPLIFIER T = 0C to +85C (MAX1953/MAX1954) 0.788 0.8 0.812 A T = -40C to +85C (MAX1953/MAX1954) 0.776 0.8 0.812 A FB Regulation Voltage V V V REFIN REFIN MAX1957 only V REFIN - 8mV + 8mV Transconductance 70 110 160 S FB Input Leakage Current V = 0.9V 5 500 nA FB REFIN Input Bias Current V = 0.8V, MAX1957 only 5 500 nA REFIN FB Input Common-Mode Range -0.1 1.5 V REFIN Input Common-Mode Range MAX1957 only -0.1 1.5 V Current-Sense Amplifier Voltage Gain Low ILIM = GND (MAX1953 only) 5.67 6.3 6.93 V/V V = V or ILIM = open (MAX1953 only) ILIM IN Current-Sense Amplifier Voltage Gain 3.15 3.5 3.85 V/V MAX1954/MAX1957 2 MAX1953/MAX1954/MAX1957