Rainbow-electronics MAX1729 User Manual download pdf

EVALUATION KIT

FOLLOWS DATA SHEET

ECB and LCD Display Bias Supply with Accurate

Output Voltage and Temperature Compensation

General Description

The MAX1729 micropower step-up/step-down DC-DC

converter is ideally suited for electrically controlled bire-

fringence (ECB) and liquid-crystal-display (LCD) bias-

supply generation. It provides step-up/step-down

voltage conversion and reduces output ripple by using

a step-up DC-DC converter followed by a linear regula-

tor. This architecture permits a physically smaller induc-

tor than those used in competing SEPIC and flyback

topologies. This device features low quiescent current

(67µA typical). A logic-controlled shutdown mode fur-

ther reduces quiescent current to 0.4µA typical.

The MAX1729 features an input that dynamically

adjusts the output voltage to control display color or

contrast. It offers two feedback modes: internal and

external. Internal feedback mode allows output volt-

ages between 2.5V and 16V, and is specifically

designed to hold temperature drift to ±11ppm/°C.

External feedback mode allows the MAX1729 output

voltage range to be tailored for various displays.

An on-chip temperature sensor with a positive tempera-

ture coefficient provides compensation for LCD/ECB

display temperature characteristics. In internal feed-

back mode, the buffered temperature sensor output is

read and used to adjust the output voltage via a digital

control signal. External feedback mode features an

additional compensation method in which the tempera-

ture output is summed directly into the feedback net-

work to provide first-order negative temperature

compensation of the output voltage. The MAX1729 is

available in the space-saving 10-pin µMAX package.

Applications

ECB Display Bias & Color Adjustment

LCD Display Bias & Contrast Adjustment

Cellular Phones

Personal Digital Assistants

Features

♦ High-Accuracy Reference Voltage (±1%)

♦ ±11ppm/°C Output Voltage Drift

♦ On-Chip Temperature Sensor Output

♦ Accurate Voltage and Temperature Provide:

Consistent ECB Colors

Consistent LCD Gray-Scale Contrast

♦ +2.7V to +5.5V Input Voltage Range

♦ Output Voltage Range

+2.5V to +16V in Internal Feedback Mode

Programmable in External Feedback Mode

♦ Dynamic Control of the Output Voltage

♦ 67µA Supply Current

♦ 0.4µA Shutdown Current

♦ 10-Pin µMAX Package (1.09mm max height)

♦ Evaluation Kit Available (MAX1729EVKIT)

MAX1729

________________________________________________________________

Maxim Integrated Products

OUT

COMP

CTLIN

OUT

+2.5V to +16V

DIGITAL

PWM

CONTROLLER

GND

2.7V to 5.5V

MAX1729

REF

ADC

Typical Operating Circuit

19-1406; Rev 1; 1/99

PART

MAX1729EUB -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

Ordering Information

Pin Configuration

GND

OUTCOMP

REF

MAX1729

µMAX

TOP VIEW

CTLINFB

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

1 2 3 4 5 6 ... 11 12

Summary of Contents

Page 1 - Maxim Integrated Products

EVALUATION KIT FOLLOWS DATA SHEETECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature CompensationGeneral DescriptionThe MAX172

Page 2 - ELECTRICAL CHARACTERISTICS

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation10 ____________________________________________________

Page 3

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation_______________________________________________________

Page 4 - (Circuit of Figure 2, T

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature CompensationNOTES12 _______________________________________________

Page 5

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation2 _____________________________________________________

Page 6 - Pin Description

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation_______________________________________________________

Page 7 - Design Procedure

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation4 _____________________________________________________

Page 8

MAX1729ECB and LCD Display Bias Supply with AccurateOutput Voltage and Temperature Compensation_______________________________________________________

Page 9 - Component Selection

MAX1729Detailed DescriptionThe MAX1729 is designed to provide bias voltage forECB or LCD displays. It is composed of a step-up DC-DC converter followe

Page 10 - Chip Information

inductor current to ramp down and VPSto increase. If, atthe end of tOFF, VPS- VOUTis still too low, then anothertONis initiated immediately. Otherwise

Page 11 - 10LUMAXB.EPS

MAX1729To use a DC control signal to adjust the output voltage,use the circuit shown in Figure 4. In this configuration,VOUTis governed by the followi

Page 12

2) Given the maximum output voltage (VMAX) and mini-mum output voltage (VMIN), calculate values for R3 andR4 as follows:3) For first-order temperature

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Summary of Contents

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