MAX1639 19-1337 Rev 1 8/05 High-Speed Step-Down Controller with Synchronous Rectification for CPU Power General Description Features The MAX1639 is an ultra-high-performance, step-down Better than 1% Output Accuracy Over DC-DC controller for CPU power in high-end computer Line and Load systems. Designed for demanding applications in which Greater than 90% Efficiency Using N-Channel output voltage precision and good transient response are MOSFETs critical for proper operation, it delivers over 35A from 1.1V Pin-Selected High Switching Frequency: to 4.5V with 1% total accuracy from a +5V 10% supply. 300kHz, 600kHz, or 1MHz Excellent dynamic response corrects output transients caused by the latest dynamically clocked CPUs. This Over 35A Output Current controller achieves over 90% efficiency by using synchro- Resistor-Divider Adjustable Output from nous rectification. Flying-capacitor bootstrap circuitry 1.1V to 4.5V drives inexpensive, external N-channel MOSFETs. Current-Mode Control for Fast Transient The switching frequency is pin-selectable for 300kHz, Response and Cycle-by-Cycle Current-Limit 600kHz, or 1MHz. High switching frequencies allow the Protection use of a small surface-mount inductor and decrease out- put filter capacitor requirements, reducing board area Short-Circuit Protection with Foldback Current and system cost. Limiting Output overvoltage protection is enforced by a crowbar Crowbar Overvoltage Protection circuit that turns on the low-side MOSFET with 100% Power-Good (PWROK) Output duty factor when the output is 200mV above the normal regulation point. Other features include internal digital Digital Soft-Start soft-start, a power-good output, and a 3.5V 1% refer- High-Current (2A) Drive Outputs ence output. The MAX1639 is available in a 16-pin narrow SOIC package. Typical Operating Circuit Applications Local DC-DC Converters for CPUs INPUT +5V Workstations V V DD CC Desktop Computers AGND BST LAN Servers TO V DD MAX1639 DH GTL Bus Termination OUTPUT LX 1.1V TO 4.5V PWROK DL Ordering Information PGND PART TEMP RANGE PIN-PACKAGE MAX1639ESE 40C to +85C 16 Narrow SO REF CSH MAX1639ESE+ 40C to +85C 16 Narrow SO CSL +Denotes lead-free packages. FREQ FB Pin Configuration appears at end of data sheet. CC1 CC2 Maxim Integrated Products 1 For free samples & the latest literature: High-Speed Step-Down Controller with Synchronous Rectification for CPU Power ABSOLUTE MAXIMUM RATINGS V , V , PWROK to AGND....................................-0.3V to +6V Continuous Power Dissipation (T = +70C) DD CC A PGND to AGND ..................................................................0.3V 16-Pin Narrow SO (derate 8.70mW/C above +70C) ....696mW CSH, CSL to AGND....................................-0.3V to (V + 0.3V) SO ...........................................................................65C/W CC JC DL to PGND................................................-0.3V to (V + 0.3V) Operating Temperature Range DD REF, CC1, CC2, FREQ, FB to AGND .........-0.3V to (V + 0.3V) MAX1639ESE....................................................-40C to +85C CC BST to PGND..........................................................-0.3V to +12V Storage Temperature Range .............................-65C to +160C BST to LX..................................................................-0.3V to +6V Lead Temperature (soldering, 10s) .................................+300C DH to LX.............................................(LX - 0.3V) to (BST + 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 = +5V, PGND = AGND = 0V, FREQ = REF, T = 0C to +85C, unless otherwise noted.) DD CC A PARAMETER CONDITIONS MIN TYP MAX UNITS T = +25C to +85C 1.089 1.111 Includes line and load A FB Voltage V regulation errors T = 0C to +85C 1.083 1.117 A Input Voltage Range V = V 4.5 5.5 V CC DD Input Undervoltage Lockout V rising edge, 1% hysteresis 4.0 4.2 V CC FB overdrive = 60mV 2.5 Operating mode FB overdrive = 0V 5 V = V CC DD V Supply Current (I ) mA CC CC = 5.5V Shutdown V = 0V 3.6 10 REF mode V = V = 5.5V, FB forced 60mV above CC DD V Supply Current (I ) 0.1 mA DD DD regulation point, operating or standby mode Reference Voltage No load 3.465 3.5 3.535 V Reference Load Regulation 0A < I < 100A 10 mV REF Reference Undervoltage Lockout Rising edge, 1% hysteresis 2.7 3.0 V Reference Short-Circuit Current V = 0V 0.5 4.0 mA REF AC Load Regulation CSH - CSL = 0mV to 80mV 1 % DC Load Regulation CSH - CSL = 0mV to 80mV 0.1 % Rising FB, 1% hysteresis with respect to V -7.5 -6 -4.5 REF PWROK Trip Level % Falling FB, 1% hysteresis with respect to V 6.5 8 9.5 REF PWROK Output Voltage Low I = 2mA, V = 4.5V 0.4 V SINK CC PWROK Output Current High PWROK = 5.5V 1 A FREQ = V 850 1000 1150 CC Switching Frequency FREQ = REF 540 600 660 kHz FREQ = AGND 255 300 345 Maximum Duty Cycle FREQ = V 85 90 % CC GND (low) 0.2 FREQ Input Voltage FREQ Input Voltage REF (mid) 3.3 3.7 V V (high) V - 0.1 CC CC 2 MAX1639