19-1337; Rev 0; 2/98
Hig h -S p e e d S t e p -Do w n Co n t ro lle r w it h
S yn c h ro n o u s Re c t ific a t io n fo r CP U P o w e r
MAX1639
________________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
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 synchro-
nous rectification. Flying-capacitor bootstrap circuitry
drives inexpensive, external N-channel MOSFETs.
♦ 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
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 out-
put filter capacitor requirements, reducing board area
and system cost.
♦ 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% refer-
ence output. The MAX1639 is available in a 16-pin
narrow SOIC package.
♦ Crowbar Overvoltage Protection
♦ Power-Good (PWROK) Output
♦ Digital Soft-Start
♦ High-Current (2A) Drive Outputs
__________ Typ ic a l Op e ra t in g Circ u it
________________________Ap p lic a t io n s
Local DC-DC Converters for CPUs
Workstations
INPUT
+5V
V
DD
V
CC
Desktop Computers
AGND
BST
LAN Servers
TO V
DD
MAX1639
DH
LX
GTL Bus Termination
OUTPUT
1.1V TO 4.5V
PWROK
DL
_______________Ord e rin g In fo rm a t io n
PGND
PART
TEMP. RANGE
PIN-PACKAGE
MAX1639ESE
-40°C to +85°C
16 Narrow SO
REF
CSH
CSL
Pin Configuration appears at end of data sheet.
FREQ
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.