MAX8650 19-3973 Rev 1 8/08 4.5V to 28V Input Current-Mode Step- Down Controller with Adjustable Frequency General Description Features The MAX8650 synchronous PWM buck controller oper- Operates from 4.5V to 28V Supply ates from a 4.5V to 28V input and generates an 1% FB Voltage Accuracy Over Temperature adjustable 0.7V to 5.5V output voltage at loads up to 25A. Adjustable Output Voltage Down to 0.7V or REFIN The MAX8650 uses a peak current-mode control archi- tecture with an adjustable (200kHz to 1.2MHz) constant Adjustable Switching Frequency or External switching frequency and is externally synchronizable. The Synchronization from 200kHz to 1.2MHz ICs current limit uses the inductors DC resistance to 180 Phase-Shifted Clock Output improve efficiency or an external sense resistor for high accuracy. The current-limit threshold is adjusted with an Adjustable Overcurrent Limit external resistor. Foldback-type current limit can be Adjustable Foldback Current Limit implemented to reduce the power dissipation in overload or short-circuit conditions. Short-circuit protection is Adjustable Slope Compensation provided based on sensing the current in the low-side Selectable Current-Limit Mode: Latch-Off or MOSFET. A reference input is provided for use with a Automatic Recovery high-accuracy external reference or for double-data-rate (DDR)-tracking applications. Monotonic Output-Voltage Rise at Startup Monotonic prebiased startup is available for a safe-start Output Sources and Sinks Current in applications where the output capacitor may have an initial charge. This feature prevents the output from Enable Input pulling low during startup, which is a common charac- Power-OK (POK) Output teristic of conventional buck regulators. Adjustable Soft-Start A 180 out-ofphase synchronization output is available for synchronizing with another converter. Independently Adjustable Overvoltage Protection Applications Ordering Information Base Stations DDR PART TEMP RANGE PIN-PACKAGE Network and Telecom Power Modules 24 QSOP MAX8650EEG+ -40C to +85C Storage IBA Applications +Denotes a lead-free/RoHS-compliant package. Servers Pin Configuration appears at end of data sheet. Typical Operating Circuit R2 R1 V IN SYNC 7V TO 28V 1 2 FSYNC MODE C1 D2 EN 4 ON 11 EN BST OFF POK 5 24 VOUT POK DH L1 0.7V TO 5.5V SYNCO C2 3 6 Q1 SYNCO LX MAX8650EEG 23 C5 7 SCOMP R8 DL R3 C6 22 Q2 ILIM2 8 PGND 21 C7 REFIN 9 C3 VL 20 SS 10 C8 IN R4 16 C10 R9 C9 ILIM1 12 C4 AVL R5 19 COMP 14 CS+ R6 18 FB 15 C11 R7 CS- 17 13 OVP GND Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE4.5V to 28V Input Current-Mode Step-Down Controller with Adjustable Frequency ABSOLUTE MAXIMUM RATINGS IN, EN to GND ........................................................-0.3V to +30V AVL, FB, POK, COMP, SS, MODE, REFIN to GND .....-0.3V to +6V BST to LX...............................................................-0.3V to +7.5V CS+, CS- to GND .....................................................-0.3V to +6V DH to LX ....................................................-0.3V to (V + 0.3V) PGND to GND .......................................................-0.3V to +0.3V BST LX to GND .................... -1V (-2.5V for < 50ns transient) to +30V Continuous Power Dissipation (T = +70C) A DL to PGND.................................................-0.3V to (V + 0.3V) 24-Pin QSOP (derate 9.5mW/C above +70C)..........762mW VL ILIM2, ILIM1, SYNCO, FSYNC, OVP, Junction Temperature......................................................+150C SCOMP to GND .....................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +150C AVL VL to PGND ...........................................................-0.3V to +7.5V Lead Temperature (soldering, 10s) .................................+300C 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 = 12V, V - V = 6.5V, T = -40C to +85C. Typical values are at T = +25C, unless otherwise noted.) (Note 1) IN BST LX A A PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Input Voltage Range VL = IN for V < 7V 4.5 28.0 V IN Quiescent Supply Current V = 0.75V, no switching 2 3 mA FB EN = GND, V 28V 10 IN Shutdown Supply Current A I + I + I IN VL AVL EN = GND, V = V = V = 5V 32 AVL VL IN AVL Undervoltage-Lockout Trip V rising, 3% typ hysteresis 3.90 4.15 4.40 V AVL Level Minimum output voltage is limited by minimum duty cycle Output Voltage Adjust Range 0.7 5.5 V and external components VL Regulation Voltage 7V < V < 28V, 1mA < I < 40mA 6.0 6.5 7.0 V IN LOAD VL Output Current 40 mA AVL Regulation Voltage 5.5V < V < 7V, 1mA < I < 10mA 4.900 4.975 5.050 V VL LOAD AVL Output Current 10 mA SOFT-START SS Shutdown Resistance From SS to GND, V = 0V 20 100 EN SS Soft-Start Current V = 0.625V 18 23 28 A SS REFIN INPUT V - AVL REFIN Dual Mode Threshold V V AVL 1.0V REFIN Input Bias Current V = 0.7V to 1.5V -250 +250 nA REFIN REFIN Input Voltage Range 0 1.5 V Dual Mode is a trademark of Maxim Integrated Products, Inc. 2 MAX8650