Rainbow-electronics MAX1771 Manual de usuario descargar pdf

General Description

The MAX1771 step-up switching controller provides

90% efficiency over a 30mA to 2A load. A unique cur-

rent-limited pulse-frequency-modulation (PFM) control

scheme gives this device the benefits of pulse-width-

modulation (PWM) converters (high efficiency at heavy

loads), while using less than 110µA of supply current (vs.

2mA to 10mA for PWM converters).

This controller uses miniature external components. Its

high switching frequency (up to 300kHz) allows sur-

face-mount magnetics of 5mm height and 9mm diame-

ter. It accepts input voltages from 2V to 16.5V. The

output voltage is preset at 12V, or can be adjusted

using two resistors.

The MAX1771 optimizes efficiency at low input voltages

and reduces noise by using a single 100mV current-limit

threshold under all load conditions. A family of similar

devices, the MAX770–MAX773, trades some full-load

efficiency for greater current-limit accuracy; they provide

a 200mV current limit at full load, and switch to 100mV

for light loads.

The MAX1771 drives an external N-channel MOSFET

switch, allowing it to power loads up to 24W. If less power

is required, use the MAX756/MAX757 or MAX761/MAX762

step-up switching regulators with on-board MOSFETs. An

evaluation kit is available.

Applications

Positive LCD-Bias Generators

Flash Memory Programmers

High-Power RF Power-Amplifier Supply

Palmtops/Hand-Held Terminals

Battery-Powered Applications

Portable Communicators

Features

♦ 90% Efficiency for 30mA to 2A Load Currents

♦ Up to 24W Output Power

♦ 110µA (max) Supply Current

♦ 5µA (max) Shutdown Current

♦ 2V to 16.5V Input Range

♦ Preset 12V or Adjustable Output Voltage

♦ Current-Limited PFM Control Scheme

♦ Up to 300kHz Switching Frequency

♦ Evaluation Kit Available

Ordering Information

MAX1771

12V or Adjustable, High-Efficiency,

Low I

, Step-Up DC-DC Controller

________________________________________________________________ Maxim Integrated Products 1

GND

AGND

REF

SHDN

V+

EXT

TOP VIEW

MAX1771

DIP/SO

Pin Configuration

FB AGND GND

V+

EXT

REF

SHDN

ON/OFF

OUTPUT

12V

INPUT

2V TO V

OUT

MAX1771

Typical Operating Circuit

PART TEMP RANGE PIN-PACKAGE

MAX1771CPA 0°C to +70°C 8 Plastic DIP

MAX1771CSA 0°C to +70°C 8 SO

MAX1771C/D 0°C to +70°C Dice*

MAX1771EPA -40°C to +85°C 8 Plastic DIP

MAX1771ESA -40°C to +85°C 8 SO

MAX1771MJA -55°C to +125°C 8 CERDIP**

19-0263; Rev 2; 3/02

EVALUATION KIT MANUAL

AVAILABLE

* Contact factory for dice specifications.

** Contact factory for availability and processing to MIL-STD-883B.

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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Indice de contenidos

Pagina 1 - , Step-Up DC-DC Controller

General DescriptionThe MAX1771 step-up switching controller provides 90% efficiency over a 30mA to 2A load. A unique cur-rent-limited pulse-frequency-

Pagina 2

MAX1771approximately 2µs; select an inductor that allows the cur-rent to ramp up to ILIM.The standard operating circuits use a 22µH inductor. If a dif

Pagina 3

Power Transistor SelectionUse an N-channel MOSFET power transistor with theMAX1771.To ensure the external N-channel MOSFET (N-FET) isturned on hard, u

Pagina 4

MAX177112V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller12_________________________________________________________________________

Pagina 5