Rainbow-electronics MAX1638 User Manual download pdf

_______________General Description

The 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 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.

The MAX1638 is available in 24-pin SSOP and QSOP

(future package) packages, and offers additional fea-

tures such as a digitally programmable output;

adjustable transient response; and selectable 0.5%, 1%,

or 2% AC load regulation. Fast recovery from load tran-

sients is ensured by a GlitchCatcher™ current-boost cir-

cuit 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% refer-

ence output.

________________________Applications

Pentium Pro™, Pentium II™, PowerPC™, Alpha™,

and K6™ Systems

Workstations

Desktop Computers

LAN Servers

GTL Bus Termination

____________________________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 Specification

MAX1638

High-Speed Step-Down Controller with

Synchronous Rectification for CPU Power

________________________________________________________________

Maxim Integrated Products

19-1313; Rev 0; 11/97

PART

MAX1638EAG

MAX1638EEG* -40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

24 SSOP

24 QSOP

______________Ordering Information

__________Typical Operating Circuit

Pin Configuration appears at end of data sheet.

Future product—contact factory for package availability.

Pentium Pro and Pentium II are trademarks of Intel Corp.

PowerPC is a trademark of IBM Corp.

Alpha is a trademark of Digital Equipment Corp.

K6 is a trademark of Advanced Micro Devices.

GlitchCatcher is a trademark of Maxim Integrated Products.

AGND

REF

FREQ

CC1

CC2

PWROK

BST

PGND

TO V

CSH

OUTPUT

1.3V TO 4.5V

INPUT

+5V

CSL

MAX1638

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.

EVALUATION KIT

AVAILABLE

1 2 3 4 5 6 ... 15 16

Summary of Contents

Page 1 - AVAILABLE

_______________General DescriptionThe MAX1638 is an ultra-high-performance, step-downDC-DC controller for CPU power in high-end computersystems. Desig

Page 2 - ELECTRICAL CHARACTERISTICS

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power10 _________________________________________________________________

Page 3

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

Page 4

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power12 _________________________________________________________________

Page 5

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

Page 6

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power14 _________________________________________________________________

Page 7

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

Page 8 - OSCILLATOR

__________Applications InformationEfficiency ConsiderationsRefer to the MAX796–MAX799 data sheet for informa-tion on calculating losses and improving

Page 9 - Internal Reference

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power2 __________________________________________________________________

Page 10 - Ω (max)

ELECTRICAL CHARACTERISTICS (continued)(VDD= VCC = D4 = +5V, PGND = AGND = D0–D3 = 0V, FREQ = REF, TA= 0°C to +85°C, unless otherwise noted.) MAX1638__

Page 11 - Board Layout Considerations

VMAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power4 _________________________________________________________________

Page 12

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

Page 13 - Settings

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power6 __________________________________________________________________

Page 14 - Choosing the MOSFET Switches

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

Page 15

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power8 __________________________________________________________________

Page 16 - Efficiency Considerations

MAX1638High-Speed Step-Down Controller withSynchronous Rectification for CPU Power____________________________________________________________________

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Rainbow-electronics MAX1638 User Manual

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