MAX1639

Better than ±1% Output Accuracy Over Line and Load
Greater than 90% Efficiency Using N-Channel MOSFETs
Pin-Selected High Switching Frequency: 300kHz, 600kHz, or 1MHz
Over 35A Output Current
Resistor-Divider Adjustable Output from 1.1V to 4.5V
Current-Mode Control for Fast Transient Response and Cycle-by-Cycle Current-Limit Protection
Short-Circuit Protection with Foldback Current Limiting
Crowbar Overvoltage Protection
Power-Good (PWROK) Output
Digital Soft-Start
High-Current (2A) Drive Outputs

Local DC-DC Converters for CPUs Workstations Desktop Computers LAN Servers GTL Bus Termination

VDD, VCC, PWROK to AGND......................................................-0.3V to +6V
PGND to AGND ..................................................................................±0.3V
CSH, CSL to AGND......................................................-0.3V to (VCC + 0.3V)
DL to PGND................................................................-0.3V to (VDD + 0.3V)
REF, CC1, CC2, FREQ, FB to AGND ............................-0.3V to (VCC + 0.3V)
BST to PGND..........................................................................-0.3V to +12V
BST to LX.................................................................................-0.3V to +6V
DH to LX.............................................................(LX - 0.3V) to (BST + 0.3V)
Continuous Power Dissipation (TA = +70°C)
16-Pin Narrow SO (derate 8.70mW/°C above +70°C) .................696mW
SO qJC...........................................................................................65°C/W
Operating Temperature Range
MAX1639ESE....................................................................-40°C to +85°C
Storage Temperature Range .........................................-65°C to +160°C
Lead Temperature (soldering, 10sec) ...........................................+300°C

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.

The MAX1639 is an ultra-high-performance, step-down DC-DC controller for CPU power in high-end computer systems. Designed for demanding applications in which output voltage precision and good transient response are critical for proper operation, it delivers over 35A from 1.1V to 4.5V with ±1% total accuracy from a +5V ±10% supply. Excellent dynamic response corrects output transients caused by the latest dynamically clocked CPUs. This controller achieves over 90% efficiency by using synchronous rectification. Flying-capacitor bootstrap circuitry drives inexpensive, external N-channel MOSFETs.

The switching frequency is pin-selectable for 300kHz, 600kHz, or 1MHz. High switching frequencies allow the use of a small surface-mount inductor and decrease output filter capacitor requirements, reducing board area and system cost.

Output overvoltage protection is enforced by a crowbar 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 soft-start, a power-good output, and a 3.5V ±1% reference output. The MAX1639 is available in a 16-pin narrow SOIC package.