MAX8646 19-3971 Rev 2 10/07 6A, 2MHz Step-Down Regulator with Integrated Switches General Description Features The MAX8646 high-efficiency switching regulator deliv- Internal 23m R MOSFETs DS(ON) ers up to 6A load current at output voltages from 0.6V Continuous 6A Output Current to 0.9 x V . The IC operates from 2.35V to 3.6V, mak- IN 1% Output Accuracy over Load, Line, ing it ideal for on-board point-of-load and postregula- and Temperature tion applications. Total output error is less than 1% Operates from 2.35V to 3.6V Supply over load, line, and temperature ranges. Adjustable Output from 0.6V to (0.9 x V IN) The MAX8646 features fixed-frequency PWM mode Soft-Start Reduces Inrush Supply Current operation with a switching frequency range of 500kHz to 2MHz set by an external resistor. High-frequency 500kHz to 2MHz Adjustable Switching Frequency operation allows for an all-ceramic capacitor design. Compatible with Ceramic, Polymer, and The high operating frequency also allows for small-size Electrolytic Output Capacitors external components. VID-Selectable Output Voltages The low-resistance on-chip nMOS switches ensure high 0.6V, 0.7V, 0.8V, 1.0V, 1.2V, 1.5V, 1.8V, 2.0V, efficiency at heavy loads while minimizing critical induc- and 2.5V tances, making the layout a much simpler task with Fully Protected Against Overcurrent and respect to discrete solutions. Following a simple layout Overtemperature and footprint ensures first-pass success in new designs. Safe-Start into Prebiased Output The MAX8646 comes with a high bandwidth (> 14MHz) Sink/Source Current in DDR Applications voltage-error amplifier. The voltage-mode control archi- Lead-Free, 24-Pin, 4mm x 4mm Thin QFN Package tecture and the voltage-error amplifier permit a type III compensation scheme to be utilized to achieve maxi- Ordering Information mum loop bandwidth, up to 20% of the switching fre- quency. High loop bandwidth provides fast transient TEMP PKG PART PIN-PACKAGE response, resulting in less required output capacitance RANGE CODE and allowing for all-ceramic-capacitor designs. 24 Thin QFN-EP* The MAX8646 provides two tri-state logic inputs to MAX8646ETG+ -40C to +85C T2444-4 4mm x 4mm select one of nine preset output voltages. The preset +Denotes a lead-free package. output voltages allow customers to achieve 1% out- *EP = Exposed pad. put-voltage accuracy without using expensive 0.1% resistors. In addition, the output voltage can be set to Typical Operating Circuit any customer value by either using two external resis- tors at the feedback with 0.6V internal reference or INPUT applying an external reference voltage to the REFIN 2.4V, 3.6V IN BST input. The MAX8646 offers programmable soft-start time using one capacitor to reduce input inrush current. OUTPUT MAX8646 EN 1.8V, 6A The MAX8646 is available in a lead-free, 24-pin, 4mm x LX 4mm, thin QFN package. V DD OUT Applications PGND POLs CTL1 ASIC/CPU/DSP Core and I/O Voltages FB CTL2 DDR Power Supplies FREQ Base-Station Power Supplies REFIN Telecom and Networking Power Supplies VDD SS COMP RAID Control Power Supplies PREBIAS PWRGD GND Pin Configuration appears at end of data sheet. 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 AVAILABLE6A, 2MHz Step-Down Regulator with Integrated Switches ABSOLUTE MAXIMUM RATINGS IN, V , PWRGD to GND ......................................-0.3V to +4.5V Continuous Power Dissipation (T = +70C) DD A COMP, FB, REFIN, OUT, (derate 27.8mW/C above +70C)..........................2222.2mW CTL , EN, SS, FREQ to GND...................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C DD LX Current (Note 1).....................................................-8A to +8A Junction Temperature......................................................+150C BST to LX..................................................................-0.3V to +4V Storage Temperature Range .............................-65C to +150C PGND to GND .......................................................-0.3V to +0.3V Lead Temperature (soldering, 10s) .................................+300C Note 1: LX has internal clamp diodes to GND and IN. Applications that forward bias these diodes should take care not to exceed the ICs package power dissipation limits. 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 = 3.3V, V = 0.5V, T = -40C to +85C, typical values are at T = +25C, circuit of Figure 1, unless otherwise noted.) FB IN DD A A (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS IN/V DD IN and V Voltage Range 2.35 3.60 V DD V = 2.5V 4 4.6 f = 1MHz, no load, IN S IN Supply Current mA (includes gate-drive current) V = 3.3V 5.5 IN V = 2.5V 1.4 2.3 IN V Supply Current f = 1MHz mA DD S V = 3.3V 2 IN Total Shutdown Current from IN V = V = V - V = 3.6V, V = 0V 13 A IN DD BST LX EN and V DD V rising 2 2.1 DD V V Undervoltage Lockout DD LX starts/stops switching V falling 1.8 1.9 DD Threshold Deglitching 2 s BST T = +25C 5 V = V = V = 3.6V, A BST DD IN BST Supply Current A V = 3.6V or 0V, V = 0V LX EN T = +85C 10 A PWM COMPARATOR PWM Comparator Propagation 10mV overdrive 20 ns Delay COMP COMP Clamp Voltage, High V = 2.35V to 3.6V 2 V IN COMP Slew Rate 1.4 V/s PWM Ramp Amplitude 1V COMP Shutdown Resistance From COMP to GND, V = V = 0V 8 EN SS ERROR AMPLIFIER Select Preset Output-Voltage Accuracy REFIN = SS -1 from +1 % Table 1 FB Regulation Accuracy Using CTL1 = CTL2 = GND 0.594 0.600 0.606 V External Resistors FB to OUT Resistor All VID settings except CTL1 = CTL2 = GND 5 8 11 k Open-Loop Voltage Gain 1k from COMP to GND 115 dB 2 MAX8646