MAX1638 19-1313 Rev 1 8/05 High-Speed Step-Down Controller with Synchronous Rectification for CPU Power General Description Features Better than 1% Output Accuracy Over The MAX1638 is an ultra-high-performance, step-down Line and Load DC-DC controller for CPU power in high-end computer 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 1.3V Pin-Selected High Switching Frequency (300kHz, to 3.5V with 1% total accuracy from a +5V 10% supply. 600kHz, or 1MHz) Excellent dynamic response corrects output transients Over 35A Output Current caused by the latest dynamically clocked CPUs. This controller achieves over 90% efficiency by using synchro- Digitally Programmable Output from 1.3V to 3.5V nous rectification. Flying-capacitor bootstrap circuitry Current-Mode Control for Fast Transient drives inexpensive, external N-channel MOSFETs. Response and Cycle-by-Cycle Current-Limit The switching frequency is pin-selectable for 300kHz, Protection 600kHz, or 1MHz. High switching frequencies allow the Short-Circuit Protection with Foldback Current use of a small surface-mount inductor and decrease out- Limiting put filter capacitor requirements, reducing board area Glitch-Catcher Circuit for Fast Load-Transient and system cost. Response The MAX1638 is available in 24-pin SSOP and QSOP Crowbar Overvoltage Protection (future package) packages, and offers additional fea- Power-Good (PWROK) Output tures such as a digitally programmable output adjustable transient response and selectable 0.5%, 1%, Digital Soft-Start or 2% AC load regulation. Fast recovery from load tran- High-Current (2A) Drive Outputs sients is ensured by a GlitchCatcher current-boost cir- Complies with Intel VRM 8.2 Specification cuit that eliminates delays caused by the buck inductor. Output overvoltage protection is enforced by a crowbar Typical Operating Circuit circuit that turns on the low-side MOSFET with 100% duty factor when the output is 200mV above the normal regulation point. Other features include internal digital INPUT +5V soft-start, a power-good output, and a 3.5V 1% refer- ence output. V V DD CC AGND BST Applications Pentium Pro, Pentium II, PowerPC, Alpha, TO V DD MAX1638 DH and K6 Systems Workstations OUTPUT LX 1.3V TO 4.5V Desktop Computers PWROK LAN Servers D0 DL D1 GTL Bus Termination D2 PGND D3 Ordering Information D4 PART TEMP RANGE PIN-PACKAGE REF CSH MAX1638EAG -40C to +85C 24 SSOP LG CSL MAX1638EAG+ -40C to +85C 24 QSOP FREQ +Denotes lead-free package. FB CC1 Pin Configuration appears at end of data sheet. CC2 Pentium Pro and Pentium II are trademarks of Intel Corp. PowerPC is a trademark of IBM Corp. Alpha is a trademark of Digital Equipment Corp. K6 is a trademark of Advanced Micro Devices. GlitchCatcher is a trademark of Maxim Integrated Products. 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. EVALUATION KIT AVAILABLEHigh-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 QSOP (derate 8.70mW/C above +70C).....................696mW CSH, CSL to AGND....................................-0.3V to (V + 0.3V) QSOP ..................................................................40C/W CC JC NDRV, PDRV, DL to PGND.........................-0.3V to (V + 0.3V) SSOP (derate 8.00mW/C above +70C) .....................640mW DD REF, CC1, CC2, LG, D0D4, FREQ, SSOP ..................................................................45C/W JC FB to AGND.............................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-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 = D4 = +5V, PGND = AGND = D0D3 = 0V, FREQ = REF, T = 0C to +85C, unless otherwise noted.) DD CC A PARAMETER CONDITIONS MIN TYP MAX UNITS T = +25C to +85C 1 Over line and load A Output Voltage (FB) Accuracy % (Note 1) T = 0C to +85C 1.5 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 = 200mV 2.5 Operating mode FB overdrive = 0V 5 V = V CC DD V Supply Current mA CC = 5.5V DAC code = 11111 0.3 Shutdown mode V = 0V 3.6 10 REF V = V = 5.5V, FB forced 200mV above CC DD V Supply Current 0.1 mA 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 LG = GND 0.5 AC Load Regulation CSH - CSL = LG = REF 1 % (Note 2) 0mV to 80mV LG = V 2 CC LG = GND 0.05 DC Load Regulation CSH - CSL = LG = REF 0.1 % (Note 2) 0mV to 80mV LG = V 0.2 CC 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 2 MAX1638