Rainbow-electronics MAX781 Manual do Utilizador descarregar pdf (Página 1)

_______________General Description

The MAX781 is a system-engineered power-supply con-

troller for subnotebook computers, PDAs, or similar bat-

tery-powered equipment. It provides high-performance,

step-down (buck), pulse-width modulated (PWM) control

for generating +3.3V and constant-current battery charg-

ing. Dual PCMCIA VPP outputs are powered by a regulat-

ed flyback winding. Five high-side gate drivers and a

buffered analog multiplexer are also included. All func-

tions are controlled by an SPI/Microwire™ compatible

four-wire serial interface.

The MAX781 generates +3.3V with high efficiency through

synchronous rectification and PWM operation at heavy

loads. It uses Idle Mode™ operation at light loads. Only

small external components are required because of the

device’s high switching frequency (300kHz) and advanced

current-mode PWM architecture that allows for output

capacitance as low as 50µF per ampere of load.

The MAX781 is configured by 32 bits of serial data. These

bits select the operating mode, set the switch-mode bat-

tery charger current level, select one of eight analog multi-

plexer channels, and turn on/off the five high-side gate

drivers. A status byte read from the serial interface indi-

cates if the battery has been removed, if the DC charging

source has been connected, or if there is a fault condition

on the +3.3V output. An interrupt output signals the CPU if

a status signal changes.

____________________________Features

♦ +3.3V Step-Down Controller

♦ Dual PCMCIA 2.0 Compatible VPP Outputs

(0V/3.3V/5V/12V)

♦ Digitally Adjustable Switching Current Source for

Battery Charging

♦ 5 High-Side Switch Gate-Driver Outputs

♦ SPI Serial Interface

♦ 300kHz Switching Frequency

♦ Oscillator SYNC Input

♦ 2.5V ±1.5% Reference Output

♦ 36-Pin SSOP Package

________________________Applications

Subnotebook Computers

PDAs

Communicating Computers

Handy-Terminals

______________Ordering Information

MAX781

PDA/Hand-Held Computer Power Controller

________________________________________________________________

Maxim Integrated Products

MAX781

DIGITALLY

ADJUSTABLE

SWITCHING

CURRENT

SOURCE

LOAD 

SWITCHES

SUBSYSTEMS

HIGH-SIDE GATE DRIVERS



+3.3V AT 1A OR MORE



SERIAL INTERFACE

INTERRUPT

VPPA

VPPB

ANALOG MULTIPLEXER OUTPUT

DCIN

(up to 18V)

5 to 8

NiCd/NiMH

CELLS 

or

2 LION

CELLS

SELF REFRESH

DRAM

CPU

PCMCIA

SLOT B

PCMCIA

SLOT A

ADC

________________________________________________Typical Application Diagram

Call toll free 1-800-998-8800 for free samples or literature.

19-0205; Rev 0; 7/94

PART

MAX781CBX

MAX781EBX -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

36 SSOP

™

SPI is a trademark of Motorola Inc. Microwire is a trademark of National Semiconductor Corp.

Idle Mode is a trademark of Maxim Integrated Porducts.

Pin Configuration on last page.

EVALUATION KIT

AVAILABLE

1 2 3 4 5 6 ... 23 24

Resumo do Conteúdo

Página 1 - AVAILABLE

_______________General DescriptionThe MAX781 is a system-engineered power-supply con-troller for subnotebook computers, PDAs, or similar bat-tery-powe

Página 2 - ELECTRICAL CHARACTERISTICS

MAX781PDA/Hand-Held Computer Power Controller10 _____________________________________________________________________________________________________D

Página 3

MAX781PDA/Hand-Held Computer Power Controller______________________________________________________________________________________ 11nal, causing the

Página 4 - ANALOG MULTIPLEXER

MAX781PDA/Hand-Held Computer Power Controller12 ______________________________________________________________________________________CEOUTPUT FROM C

Página 5 - CHARGER OUTPUT CURRENT

MAX781PDA/Hand-Held Computer Power Controller______________________________________________________________________________________ 13The 3VSTAT compa

Página 6 - TURNS / PRIMARY TURNS) = 3.5

MAX781PDA/Hand-Held Computer Power Controller14 ______________________________________________________________________________________DHI high-side dr

Página 7 - VARIABLE SWITCHING FREQUENCY

MAX781PDA/Hand-Held Computer Power Controller______________________________________________________________________________________ 15Gate DriversGD1

Página 8

MAX781_Component Selection and Layout3.3V OutputInput and Output Bypass CapacitorsCapacitor C15 ensures that the buck regulator has alow AC-impedance

Página 9

R7 can be as large as 0.082Ω x 1.01 = 0.0828Ω, yield-ing a minimum peak current limit of 80mV / 0.0828Ω =0.966A.Use the spreadsheet in Listings 1 and

Página 10 - Table 2. Operating Modes

MAX781VPPA and VPPB are linear regulated from VHI, so thepower consumed by loads on VPPA or VPPB equalsthe VHI voltage times the load current. Barrin

Página 11

MAX781PDA/Hand-Held Computer Power Controller______________________________________________________________________________________ 19Table 9. Design

Página 12 - • • •

MAX781PDA/Hand-Held Computer Power Controller2 _______________________________________________________________________________________ABSOLUTE MAXIMUM

Página 13 - 3.3V Output

MAX781PDA/Hand-Held Computer Power Controller20 ______________________________________________________________________________________MAX781BATTVCHGCO

Página 14 - VPP Regulator

Interfacing the MAX781 to an IBM Compatible PCFigure 1 shows the MAX781 typical operating circuit.On power-up, with 4.8V < BATT < 18V and CE = S

Página 15 - Battery Charger

MAX781PDA/Hand-Held Computer Power Controller22 ______________________________________________________________________________________Listing 3. MAX7

Página 16

MAX781PDA/Hand-Held Computer Power Controller______________________________________________________________________________________ 23________________

Página 17 - Design Example

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses arei

Página 18 - Specifications

MAX781PDA/Hand-Held Computer Power Controller_______________________________________________________________________________________ 3ELECTRICAL CHARA

Página 19 - Table 10. Component Suppliers

MAX781PDA/Hand-Held Computer Power Controller4 _______________________________________________________________________________________ELECTRICAL CHARA

Página 20

MAX781PDA/Hand-Held Computer Power Controller_______________________________________________________________________________________ 5TIMING CHARACTER

Página 21 - IBM Compatible PC

MAX781PDA/Hand-Held Computer Power Controller6 _______________________________________________________________________________________________________

Página 22

MAX781PDA/Hand-Held Computer Power Controller_______________________________________________________________________________________7101 10 100 10003O

Página 23 - TOP VIEW

MAX781PDA/Hand-Held Computer Power Controller8 _______________________________________________________________________________________________________

Página 24 - 21-0032A

VPP LINEARREGULATORSBIASGEN+3.3V LINEAR REGULATORVCHGBATTUVLOSHDNAGNDCESCLKDINAUXINAOUTTEMP2.5VREFERENCE+3.3V SWITCHINGREGULATORSERIAL INTERFACEA

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Rainbow-electronics MAX781 Manual do Utilizador Página 1

Consulte online ou descarregue Manual do Utilizador para Sensores Rainbow-electronics MAX781. Rainbow Electronics MAX781 User Manual Manual do Utilizador

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Rainbow-electronics MAX781 Manual do Utilizador Página 1

Consulte online ou descarregue Manual do Utilizador para Sensores Rainbow-electronics MAX781. Rainbow Electronics MAX781 User Manual Manual do Utilizador

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