MAX8643A 19-0767 Rev 2 10/09 3A, 2MHz Step-Down Regulator with Integrated Switches General Description Features The MAX8643A high-efficiency switching regulator Internal 37m R MOSFETs DSON delivers up to 3A load current at output voltages from Continuous 3A Output Current 0.6V to (0.9 x V ). The IC operates from 2.35V to 3.6V, IN 1% Output Accuracy Over Load, Line, making it ideal for on-board point-of-load and postregu- and Temperature lation applications. Total output error is less than 1% Operates from 2.35V to 3.6V Supply over load, line, and temperature. Adjustable Output from 0.6V to (0.9 x V ) The MAX8643A features fixed-frequency PWM mode IN operation with a switching frequency range of 500kHz Soft-Start Reduces Inrush Supply Current 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 0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, and 2.5V efficiency at heavy loads while minimizing critical induc- tances, making the layout a much simpler task with Fully Protected Against Overcurrent respect to discrete solutions. Following a simple layout and Overtemperature and footprint ensures first-pass success in new designs. Safe-Start into Prebiased Output The MAX8643A 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- mum loop bandwidth, up to 20% of the switching fre- Ordering Information quency. High loop bandwidth provides fast transient response, resulting in less required output capacitance PART TEMP RANGE PIN-PACKAGE and allowing for all-ceramic capacitor designs. M AX8643A E TG+ -40 C to +8 5C 24 Thin QFN-EP* The MAX8643A provides two three-state logic inputs to M AX8643A E TG/V+ - 40 C to +8 5C 24 Thin QFN-EP* select one of nine preset output voltages. The preset +Denotes a lead(Pb)-free/RoHS-compliant package. output voltages allow customers to achieve 1% out- /V denotes an automotive qualified part. put-voltage accuracy without using expensive 0.1% *EP = Exposed pad. resistors. In addition, the output voltage can be set to any customer value by either using two external resis- Typical Operating Circuit tors at the feedback with 0.6V internal reference or applying an external reference voltage to the REFIN INPUT 2.4V TO 3.6V input. The MAX8643A offers programmable soft-start IN BST time using one capacitor to reduce input inrush current. OUTPUT The MAX8643A is available in a lead-free, 24-pin, 4mm MAX8643A 1.8V, 3A EN x 4mm thin QFN package. LX V DD OUT Applications POLs PGND CTL1 ASIC/CPU/DSP Core and I/O Voltages FB CTL2 DDR Power Supplies FREQ Base-Station Power Supplies REFIN V Telecom and Networking Power Supplies DD COMP SS 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 Maxim s website at www.maxim-ic.com.3A, 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, 24-Pin TQFN-EP CTL , EN, SS, FREQ to GND...................-0.3V to (V + 0.3V) (derated 27.8mW/C above +70C)........................2222.2mW DD LX Current (Note 1).....................................................-4A to +4A Operating Temperature Range ...........................-40C to +85C BST to LX..................................................................-0.3V to +4V Junction Temperature......................................................+150C PGND to GND .......................................................-0.3V to +0.3V Storage Temperature Range .............................-65C to +150C 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.) (Note 2) FB A IN DD A 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 IN f = 1MHz, no load 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 A V = V = V = 3.6V, 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 2 MAX8643A