Features: · 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
· Digitally Programmable Output from 1.3V to 3.5V
· Current-Mode Control for Fast Transient Response and Cycle-by-Cycle Current-Limit Protection
· Short-Circuit Protection with Foldback Current Limiting
· Glitch-Catcher Circuit for Fast Load-Transient Response
· Crowbar Overvoltage Protection
· Power-Good (PWROK) Output
· Digital Soft-Start
· High-Current (2A) Drive Outputs
· Complies with Intel VRM 8.2 SpecificationApplicationPentium Pro™, Pentium II™, PowerPC™, Alpha™,
and K6™ Systems
Workstations
Desktop Computers
LAN Servers
GTL Bus TerminationPinout
SpecificationsVDD, VCC, PWROK to AGND ...................................-0.3V to 6V
PGND to AGND .............................................................±0.3V
CSH, CSL to AGND..................................-0.3V to (VCC + 0.3V)
NDRV, PDRV, DL to PGND.......................-0.3V to (VDD + 0.3V)
REF, CC1, CC2, LG, D0D4, 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)
QSOP (derate 8.70mW/°C above +70°C).................696mW
QSOP JC..................................................................40°C/W
SSOP (derate 8.00mW/°C above +70°C) ...............640mW
SSOP JC ..................................................................45°C/W
Operating Temperature Range ...................-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.
DescriptionThe MAX1638 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 1.3V to 3.5V 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.
The MAX1638 is available in 24-pin SSOP and QSOP (future package) packages, and offers additional features such as a digitally programmable output; adjustable transient response; and selectable 0.5%, 1%,or 2% AC load regulation. Fast recovery from load transients is ensured by a GlitchCatcher™ current-boost circuit that eliminates delays caused by the buck inductor. 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.
MAX1638 Data Sheet
