MAX1639 Datasheet, PDF (1/13 Pages) Maxim Integrated Products – High-Speed Step-Down Controller with Synchronous Rectification for CPU Power

19-1337; Rev 0; 2/98
EVAALVUAAILTAIOBNLEKIT
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
________________General Description
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.
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.
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.
________________________Applications
Local DC-DC Converters for CPUs
Workstations
Desktop Computers
LAN Servers
GTL Bus Termination
_______________Ordering Information
PART
MAX1639ESE
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 Narrow SO
Pin Configuration appears at end of data sheet.
____________________________Features
o Better than ±1% Output Accuracy Over
Line and Load
o Greater than 90% Efficiency Using N-Channel
MOSFETs
o Pin-Selected High Switching Frequency:
300kHz, 600kHz, or 1MHz
o Over 35A Output Current
o Resistor-Divider Adjustable Output from
1.1V to 4.5V
o Current-Mode Control for Fast Transient
Response and Cycle-by-Cycle Current-Limit
Protection
o Short-Circuit Protection with Foldback Current
Limiting
o Crowbar Overvoltage Protection
o Power-Good (PWROK) Output
o Digital Soft-Start
o High-Current (2A) Drive Outputs
__________ Typical Operating Circuit
V_CC
V_DD
AGND BST
TO V_{DD MAX1639 DH}
LX
PWROK
DL
PGND
INPUT
+5V
OUTPUT
1.1V TO 4.5V
REF
CSH
CSL
FREQ
CC1
FB
CC2
________________________________________________________________ Maxim Integrated Products 1
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For small orders, phone [phone] ext. 3468.