Rainbow-electronics MAX8737 User Manual download pdf

General Description

The MAX8737 dual high-power linear regulator con-

trollers use external n-channel MOSFETs to generate

two independent low-voltage supplies for notebook

computers. The MAX8737 delivers low output voltages

from 0.5V to 2.5V (±5mV no-load accuracy). The exter-

nal components allow scalable current design with

loads up to 5A with excellent load regulation (1%). The

regulator operates from a low input voltage, which also

reduces the power dissipation in the external n-channel

MOSFET. The controller powers the external MOSFET

gate driver from the standard 5V system supply.

The MAX8737 includes current and thermal limits to

prevent damage to the linear regulator. The MAX8737

uses an external resistive divider to fold back the cur-

rent limit, reducing the overall power dissipation. The

MAX8737 uses an external resistive-divider in series

with the current-sense input (CS_), providing foldback

current-limit protection, and effectively reducing the

short-circuit power dissipation.

An output undervoltage timeout is available for low-cost

applications that omit the current-sense resistor. The

output undervoltage (UVP) timing depends on the mag-

nitude of the voltage at V

OUT

. The UVP detects and

shuts down the LDO if the output voltage drops out of

regulation. The controller uses an adjustable reference

input (REFIN_) to set the nominal output voltage

OUT_

), which minimizes the cost and makes the sta-

bility independent of the output voltage.

Each linear regulator features an adjustable soft-start

function, and generates a delayed power-good

(PGOOD) signal that signals when the linear regulator

is in regulation. The MAX8737 is a low-cost solution

requiring few external components and is available in a

small, 4mm x 4mm, 16-pin thin QFN package.

Applications

Notebook and Desktop Computers

Point-of-Load Regulators

MCH

and V

CCP

CPU Supplies

Low-Voltage Bias Supplies

Servers

Features

♦ Low-Cost Dual Linear Regulators

♦ Output Voltage Accuracy ±5mV

♦ Independent 0.5V to 2.5V Reference Inputs

♦ Foldback Current-Limit Protection

♦ Output Undervoltage-Lockout Protection

♦ Thermal Limit (Internal Sensor)

♦ 1.0V to 5.5V Input Supply Voltage (External FET

Drain)

♦ 5V Bias Supply Voltage

♦ Independent Power-Good Open-Drain Outputs

♦ Independent Enable Inputs

♦ Soft-Shutdown Output Discharge

♦ Low Supply Current (0.5mA)

♦ 5µA (max) Shutdown Supply Current

MAX8737

Dual, Low-Voltage Linear Regulator Controllers

with External MOSFETs

________________________________________________________________ Maxim Integrated Products 1

1234

12 11 10 9

DRV1

GND

N.C.

DRV2

N.C.

CS2

OUT2

REFIN2

CS1

OUT1

REFIN1

PGOOD2

PGOOD1

EN2

EN1

TOP VIEW

MAX8737

4mm x 4mm TQFN

Pin Configuration

19-3705; Rev 0; 5/05

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.

EVALUATION KIT

AVAILABLE

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

MAX8737ETE

-40°C to +85°C

16 Thin QFN-EP* 4mm x 4mm

MAX8737ETE+

-40°C to +85°C

16 Thin QFN-EP* 4mm x 4mm

*EP = Exposed pad.

+Denotes lead-free packaging.

1 2 3 4 5 6 ... 14 15

Summary of Contents

Page 1 - Ordering Information

General DescriptionThe MAX8737 dual high-power linear regulator con-trollers use external n-channel MOSFETs to generatetwo independent low-voltage sup

Page 2 - ELECTRICAL CHARACTERISTICS

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs10 _________________________________________________________________________

Page 3

Slow UVPIf the output drops below 80% of the nominal outputvoltage (VREFIN) for 75µs, the MAX8737 shuts down theLDO and pulls the DRV_ pin to ground.

Page 4 - MAX8737 toc03

MAX8737provide good transient response, the capacitor’s ESRshould be minimized:∆VOUT= ∆IOUTx ESRwhere ∆IOUTis the maximum peak-to-peak load currentst

Page 5

0.5%/°C); therefore, the value of RDSONat the highestoperating junction temperature should be used:where VIN_MINis the minimum input voltage at the dr

Page 6 - DISTRIBUTION

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs14 _________________________________________________________________________

Page 7 - Pin Description

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETsMaxim cannot assume responsibility for use of any circuitry other than circu

Page 8 - Detailed Description

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs2 __________________________________________________________________________

Page 9 - UVP Short-Circuit Protection

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs____________________________________________________________________________

Page 10 - Figure 2. Functional Diagram

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs4 __________________________________________________________________________

Page 11 - Design Procedure

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs____________________________________________________________________________

Page 12 - External MOSFET Selection

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs6 __________________________________________________________________________

Page 13 - PC Board Layout Guidelines

MAX8737Dual, Low-Voltage Linear Regulator Controllerswith External MOSFETs____________________________________________________________________________

Page 14 - Chip Information

MAX8737Detailed DescriptionThe MAX8737 is a dual, low-dropout, external n-chan-nel linear regulator controller for low-voltage notebookcomputer power

Page 15 - Package Information

resistor network is calculated using the short-circuitcurrent (ISHORT), the maximum load current (IMAX), cur-rent-sense resistor (RCS), the 10mV (±3mV

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Rainbow-electronics MAX8737 User Manual

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