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MAX799

Step-Down Controllers with Synchronous Rectifier for CPU Power

Maxim Integrated 

19-0221; Rev 4; 9/05

EVAALVUAAILTAIOBNLEKIT

Step-Down Controllers with

Synchronous Rectifier for CPU Power

_______________General Description

The MAX796/MAX797/MAX799 high-performance, step-

down DC-DC converters with single or dual outputs

provide main CPU power in battery-powered systems.

These buck controllers achieve 96% efficiency by using

synchronous rectification and Maxim’s proprietary Idle

Mode™ control scheme to extend battery life at full-load

(up to 10A) and no-load outputs. Excellent dynamic

response corrects output transients caused by the latest

dynamic-clock CPUs within five 300kHz clock cycles.

Unique bootstrap circuitry drives inexpensive N-channel

MOSFETs, reducing system cost and eliminating the

crowbar switching currents found in some PMOS/NMOS

switch designs.

The MAX796/MAX799 are specially equipped with a sec-

ondary feedback input (SECFB) for transformer-based

dual-output applications. This secondary feedback path

improves cross-regulation of positive (MAX796) or nega-

tive (MAX799) auxiliary outputs.

The MAX797 has a logic-controlled and synchronizable

fixed-frequency pulse-width-modulating (PWM) operating

mode, which reduces noise and RF interference in sensi-

tive mobile-communications and pen-entry applications.

The SKIP override input allows automatic switchover to

idle-mode operation (for high-efficiency pulse skipping) at

light loads, or forces fixed-frequency mode for lowest noise

at all loads.

The MAX796/MAX797/MAX799 are all available in 16-

pin DIP and narrow SO packages. See the table below

to compare these three converters.

PART

MAX796

MAX797

MAX799

MAIN OUTPUT

SPECIAL FEATURE

3.3V/5V or adj

Regulates positive secondary

voltage (such as +12V)

3.3V/5V or adj Logic-controlled low-noise mode

3.3V/5V or adj

Regulates negative secondary

voltage (such as -5V)

________________________Applications

Notebook and Subnotebook Computers

PDAs and Mobile Communicators

Cellular Phones

____________________________Features

♦ 96% Efficiency

♦ 4.5V to 30V Input Range

♦ 2.5V to 6V Adjustable Output

♦ Preset 3.3V and 5V Outputs (at up to 10A)

♦ Multiple Regulated Outputs

♦ +5V Linear-Regulator Output

♦ Precision 2.505V Reference Output

♦ Automatic Bootstrap Circuit

♦ 150kHz/300kHz Fixed-Frequency PWM Operation

♦ Programmable Soft-Start

♦ 375μA Typ Quiescent Current (VIN = 12V, VOUT = 5V)

♦ 1μA Typ Shutdown Current

_______________Ordering Information

PART†

MAX796CPE

MAX796CSE

MAX796C/D

MAX796EPE

MAX796ESE

MAX796MJE

TEMP RANGE

0°C to +70°C

0°C to +70°C

0°C to +70°C

-40°C to +85°C

-40°C to +85°C

-55°C to +125°C

PIN-PACKAGE

16 Plastic DIP

16 Narrow SO

Dice*

16 Plastic DIP

16 Narrow SO

16 CERDIP

Ordering Information continued at end of data sheet.

*Contact factory for dice specifications.

___________________Pin Configuration

TOP VIEW

SS 1

(SECFB) SKIP 2

REF 3

GND 4

SYNC 5

SHDN 6

FB 7

CSH 8

MAX796

MAX797

MAX799

16 DH

15 LX

14 BST

13 DL

12 PGND

11 VL

10 V+

9 CSL

Idle Mode is a trademark of Maxim Integrated Products.

†U.S. and foreign patents pending.

( ) ARE FOR MAX796/MAX799.

DIP/SO

________________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

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