MAX8553/MAX8554 19-3017 Rev 1 5/05 4.5V to 28V Input, Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications General Description Features The MAX8553 is a 4.5V to 28V input-voltage, synchro- Up to 25A Output-Current Capability nous step-down controller that provides a complete Quick-PWM Control for Fast Loop Response power-management solution for DDR memory. The MAX8553 generates 1/2 V voltage for VTT and REFIN Up to 95% Efficiency VTTR. The VTT and VTTR tracking voltages are main- 4.5V to 28V Input Voltage Range tained within 1% of 1/2 V . The MAX8554 is a 4.5V to REFIN 28V input voltage, nontracking step-down controller with No External Bias Supply Required a low 0.6V feedback threshold voltage. The MAX8553/ 0 to 3.6V Input REFIN Range (MAX8553) MAX8554 use Maxims proprietary Quick-PWM archi- tecture for fast transient response and operate with Automatically Sets VTT and VTTR to within 1% selectable pseudo-fixed frequencies. Both controllers of 1/2 V - (MAX8553) REFIN can operate without an external bias supply. Low 0.6V Feedback Threshold (MAX8554) The controllers operate in synchronous-rectification mode to ensure balanced current sourcing and sinking capabili- 200kHz/300kHz/400kHz/550kHz Selectable ty of up to 25A. The MAX8553/MAX8554 also provide up Switching Frequencies to 95% efficiency, making them ideal for server and point- Adjustable Foldback Current Limit of-load applications. Additionally, a low 5A shutdown current allows for longer battery life in notebook applica- Overvoltage Protection tions. Lossless current monitoring is achieved by monitor- Digital Soft-Start ing the low-side MOSFETs drain-to-source voltage. The MAX8553/MAX8554 have an adjustable foldback current limit to withstand a continuous output overload and short Typical Operating Circuit circuit. Digital soft-start provides control of inrush current during power-up. Overvoltage protection shuts the con- verter down and discharges the output capacitor. The VIN MAX8553/MAX8554 come in space-saving 16-pin QSOP +5V packages. EN/HSD DH Applications MAX8553 POK Wide-Input Power Supplies POK VL Servers and Storage Applications REFIN REFIN BST ASIC and CPU Core Voltages VOUT Notebook and LCD-PC Power Supplies V+ V+ LX DDR I and DDR II Memory Power Supplies AGTL Bus Termination Supplies DL REF ILIM PGND Ordering Information FSEL VTT PART TEMP RANGE PIN-PACKAGE VTTR MAX8553EEE -40C to +85C 16 QSOP GND VTTR MAX8554EEE -40C to +85C 16 QSOP Pin Configurations appear at end of data sheet. Quick-PWM is a trademark 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.4.5V to 28V Input, Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications ABSOLUTE MAXIMUM RATINGS V+, EN/HSD, EN, HSD to GND...............................-0.3V to +30V REF Short Circuit to GND...........................................Continuous PGND to GND .......................................................-0.3V to +0.3V Continuous Power Dissipation (T = +70C) A VTT, REFIN, POK, OUT, FB, VL to GND...................-0.3V to +6V 16-Pin QSOP (derated 8.3mW/C above +70C) ........667mW REF, VTTR, DL, ILIM, FSEL to GND ............-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C VL LX to PGND ...............................................................-2V to +30V Junction Temperature......................................................+150C BST to GND............................................................-0.3V to +36V Storage Temperature Range .............................-65C to +150C DH to LX ...................................................................-0.3V to +6V Lead Temperature (soldering, 10s) .................................+300C LX to BST..................................................................-6V to +0.3V 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 = +12V, V = V = +2.5V, V = +5V, C = 4.7F, C = 1F, C = 0.22F, V = 0V, ILIM = VL, V+ HSD EN/HSD REFIN EN VL VTTR REF FSEL PGND = LX = GND, BST = VL, T = 0C to +85C. Typical values are at T = +25C, unless otherwise specified.) A A PARAMETER CONDITIONS MIN TYP MAX UNITS V+ Input Voltage Range VL not connected to V+ 6 28 V V+ Input Voltage Range VL connected to V+ 4.5 5.5 V EN/HSD Input Voltage Range MAX8553 enabled 1.5 28.0 V EN Input Voltage Range MAX8554 enabled 1.5 28.0 V EN Input Current 23 A HSD Input Voltage Range MAX8554 enabled 1.5 28.0 V HSD Input Current 20 40 A REFIN Input Voltage Range 0 3.6 V V+ Supply Current (MAX8553) V = +1.35V 0.8 1.2 mA VTT V+ Supply Current (MAX8554) V = 630mV 0.62 0.90 mA FB REFIN Supply Current 125 250 A EN/HSD Supply Current 510 A VL Supply Current V = V = 5.5V, V = +1.35V 0.8 1.2 mA VL V+ VTT V+ Shutdown Supply Current EN/HSD = GND 3 5 A REFIN Shutdown Supply Current EN/HSD = GND 1 A VL Shutdown Supply Current V = V = +5.5V, V = 0V 5 12 A VL V+ EN/HSD VL Undervoltage-Lockout Threshold Rising edge, typical hysteresis = 40mV 4.05 4.25 4.40 V VTT VTT Input Bias Current V = +1.25V -0.15 0A VTT VTT Feedback Voltage Range 0 1.8 V V = V = +1.8V 49.5 50 50.5 REFIN EN/HSD VTT Feedback Voltage Accuracy % V REFIN V = V = +3.6V 49.5 50 50.5 REFIN EN/HSD FB Input Bias Current MAX8554, V = +600mV -0.15 0A FB 2 MAX8553/MAX8554