Rainbow-electronics MAX686 Manual de usuario descargar pdf (Pagina 1)

General Description

The MAX686 DAC-controlled boost/inverter IC converts

a positive input voltage to a positive or negative LCD

bias voltage up to +27.5V or -27.5V. The device features

an internal N-channel MOSFET switch, programmable

current limiting, and an internal 6-bit digital-to-

analog converter (DAC) for digital adjustment of the

output voltage. It comes in a small 16-pin QSOP pack-

age (same size as an 8-pin SO).

The MAX686 uses a current-limited, pulse-frequency-

modulation (PFM) control scheme to provide high effi-

ciency over a wide range of load conditions. Its high

switching frequency (up to 300kHz) allows the use of

small external components.

An LCDON output allows the LCD bias voltage to be

automatically disabled when the display logic voltage is

removed, protecting the display. The MAX686 has a

+2.7V to +5.5V input voltage range for the IC, and a

+0.8V to +27.5V input voltage range for the inductor.

Typical quiescent supply current is 65µA. Shutdown

current is 1.5µA.

The MAX686 offers high-level integration to save space,

reduce power consumption, and increase battery life,

making it an excellent choice for battery-powered

portable equipment. The MAX629 is similar to the

MAX686, except that it does not contain a built-in DAC.

Both devices have evaluation kits to facilitate designs.

Applications

Positive or Negative LCD Bias

Personal Digital Assistants

Notebook Computers

Portable Data-Collection Terminals

Palmtop Computers

Varactor Tuning Diode Bias

____________________________Features

♦ Internal 500mA, 28V N-Channel Switch

(no external FET required)

♦ Adjustable Output Voltage to +27.5V or -27.5V

♦ 6-Bit DAC-Controlled Output Voltage

♦ Up to 90% Efficiency

♦ Small 16-Pin QSOP Package

(Same size as 8-pin SO)

♦ Power-OK Indicator

♦ 65µA Quiescent Current

♦ 1.5µA Shutdown Current

♦ Up to 300kHz Switching Frequency

MAX686

DAC-Controlled Boost/Inverter

LCD Bias Supply with Internal Switch

________________________________________________________________

Maxim Integrated Products

19-1327; Rev 1; 2/98

PART

MAX686C/D

MAX686EEE -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

Dice*

16 QSOP

EVALUATION KIT

AVAILABLE

Ordering Information

Dice are specified at T

= +25°C, DC parameters only.

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.

Functional Diagram appears at end of data sheet.

MAX686

OUT

22µH

= 0.8V TO 27.5V

SHDN

POL

GND PGND

DACOUT

LCDON

REF

POK

ISET

0.1µF

MBR0530L

ON/OFF

DAC CONTROL

= 2.7V TO 5.5V

0.1µF

Typical Operating Circuit

PGND LX

N.C.

LCDON

GND

POK

REF

TOP VIEW

MAX686

QSOP

ISET

POL

SHDN

DACOUT

Pin Configuration

1 2 3 4 5 6 ... 15 16

Indice de contenidos

Pagina 1 - = +25°C, DC parameters only

General DescriptionThe MAX686 DAC-controlled boost/inverter IC convertsa positive input voltage to a positive or negative LCDbias voltage up to +27.5V

Pagina 2 - ELECTRICAL CHARACTERISTICS

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch10 ___________________________________________________________________________

Pagina 3

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

Pagina 4

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch12 ___________________________________________________________________________

Pagina 5

Feed-Forward CapacitorsParallel a feed-forward capacitor (CF) across R2 to com-pensate the feedback loop and ensure stability (Figure4). Use values up

Pagina 6

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch14 ___________________________________________________________________________

Pagina 7 - Pin Description

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

Pagina 8

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch16 ___________________________________________________________________________

Pagina 9 - Detailed Description

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch2 ____________________________________________________________________________

Pagina 10 - Design Procedure

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

Pagina 11 - Selecting Inductors

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch4 ____________________________________________________________________________

Pagina 12 - Table 1. Component Suppliers

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

Pagina 13 - Applications Information

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch6 ____________________________________________________________________________

Pagina 14 - Connecting V

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

Pagina 15 - Functional Diagram

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch8 ____________________________________________________________________________

Pagina 16 - QSOP.EPS

MAX686DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch______________________________________________________________________________

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