19-1337; Rev 1; 8/05
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High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
____________________________Features
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.
♦ Better than ±1% Output Accuracy Over
Line and Load
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.
♦ 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
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.
♦ Crowbar Overvoltage Protection
________________________Applications
__________ Typical Operating Circuit
♦ Power-Good (PWROK) Output
♦ Digital Soft-Start
♦ High-Current (2A) Drive Outputs
Local DC-DC Converters for CPUs
INPUT
+5V
Workstations
VCC
LAN Servers
TO VDD
VDD
AGND
Desktop Computers
BST
MAX1639 DH
GTL Bus Termination
LX
OUTPUT
1.1V TO 4.5V
PWROK
DL
_______________Ordering Information
PGND
PART
TEMP RANGE
PIN-PACKAGE
MAX1639ESE
40°C to +85°C
16 Narrow SO
MAX1639ESE+
40°C to +85°C
16 Narrow SO
REF
CSH
CSL
+Denotes lead-free packages.
FREQ
Pin Configuration appears at end of data sheet.
CC1
FB
CC2
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX1639
________________General Description
