Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - DC/DC voltage regulator Holder uMAX 8

General Description

The MAX1776 high-efficiency step-down converter pro-

vides an adjustable output voltage from 1.25V to V

from

supply voltages as high as 24V. An internal current-limit-

ed 0.4Ω MOSFET delivers load currents up to 600mA.

Operation to 100% duty cycle minimizes dropout volt-

age (240mV at 600mA).

The MAX1776 has a low 15µA quiescent current to

improve light-load efficiency and conserve battery life.

The device draws only 3µA while in shutdown.

High switching frequencies (up to 200kHz) allow the

use of tiny surface-mount inductors and output capaci-

tors. The MAX1776 is available in an 8-pin µMAX pack-

age, which uses half the space of an 8-pin SO. For

increased output drive capability, use the MAX1626/

MAX1627 step-down controllers, which drive an exter-

nal P-channel MOSFET to deliver up to 20W.

Applications

Notebook Computers

Distributed Power Systems

Keep-Alive Supplies

Hand-Held Devices

Features

♦ Fixed 5V or Adjustable Output

♦ 4.5V to 24V Input Voltage Range

♦ Up to 600mA Output Current

♦ Internal 0.4Ω P-Channel MOSFET

♦ Efficiency Over 95%

♦ 15µA Quiescent Supply Current

♦ 3µA Shutdown Current

♦ 100% Maximum Duty Cycle for Low Dropout

♦ Current-Limited Architecture

♦ Thermal Shutdown

♦ Small 8-µMAX Package

MAX1776

24V, 600mA Internal Switch, 100% Duty Cycle,

Step-Down Converter

________________________________________________________________ Maxim Integrated Products 1

OUT

ILIM2

INLX

ILIM

GND

µMAX

TOP VIEW

SHDN

MAX1776EUA

Pin Configuration

Ordering Information

SHDN

OUT

ILIM LX

OUT

ILIM2

GNDFB

MAX1776

µMAX

Typical Operating Circuit

19-1975; Rev 2; 7/03

PART TEMP RANGE PIN-PACKAGE

MAX1776EUA -40°C to +85°C 8 µMAX

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.

Summary of content (13 pages)

PAGE 1
9-1975; Rev 2; 7/03 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter Features ♦ Fixed 5V or Adjustable Output ♦ 4.5V to 24V Input Voltage Range ♦ Up to 600mA Output Current ♦ Internal 0.
PAGE 2
MAX1776 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter ABSOLUTE MAXIMUM RATINGS IN, SHDN, ILIM, ILIM2 to GND .................................-0.3V to 25V LX to GND.......................................................-2V to (VIN + 0.3V) OUT, FB to GND .........................................................-0.3V to 6V Peak Input Current .................................................................. 2A Maximum DC Input Current..............................................
PAGE 3
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter (Circuit of Figure 1, VIN = +12V, SHDN = IN, TA = 0°C to +85°C, unless otherwise noted.) PARAMETER Dropout Voltage SYMBOL CONDITIONS MIN VDROPOUT IOUT = 525mA, ILIM = ILIM2 = IN TYP %/V VIN = 8V/24V, 200Ω load 0.1 Load Regulation No load/full load 0.9 Low SHDN, ILIM2 High 2.4 Digital Input Leakage Current V SHDN, VILIM, VILIM2 = 0 or 24V, VIN = 24V -1 +1 Low 0.05 High Thermal Shutdown % 0.8 Digital Input Level 2.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = +12V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS -75 75 mV 10 µA LX Zero-Crossing Threshold LX Switch Leakage Current VIN = 24V, LX = GND Digital Input Level SHDN, ILIM2 Digital Input Leakage Current V SHDN, VILIM, VILIM2 = 0 or 24V, VIN = 24V Low 0.8 High V 2.4 -1 1 Low ILIM Input Level µA 0.05 High V 2.
PAGE 5
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter 0.4 0.2 -0.8 1.0 ILOAD = 500mA 80 70 65 -0.8 60 -1.0 55 9 11 13 15 17 19 21 23 25 50 5 7 9 VIN (V) VIN (V) EFFICIENCY vs. ILOAD, CIRCUIT 5, VOUTPUT = 3.3V EFFICIENCY vs. ILOAD, CIRCUIT 1, VOUTPUT = 3.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 1, components from Table 3, VIN = +12V, SHDN = IN, TA = +25°C.) QUIESCENT SUPPLY CURRENT vs. TEMPERATURE QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE QUIESCENT SUPPLY CURRENT (µA) 17.5 17.0 16.5 16.0 15.5 MAX1776 toc17 14.20 MAX1776 toc16 QUIESCENT SUPPLY CURRENT (µA) 18.0 14.15 14.10 14.05 14.00 13.95 13.90 13.85 13.80 13.75 15.0 13.
PAGE 7
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter LX WAVEFORM, CIRCUIT 1 VIN = 15V, ILOAD = 500mA STARTUP WAVEFORM, CIRCUIT 1, RLOAD = 100Ω MAX1776 toc22 MAX1776 toc23 5V 0 VSHDN 1A IL 0 1A IL 10V VLX 0 0 6V 4V VOUT 2V VOUT 50mV/div 0 2µs/div 2µs/div EFFICIENCY vs. ILOAD, CIRCUIT 3, VIN = 12V 95 L = 22µH EFFICIENCY (%) L = 22µH, 0.6A 90 85 L = 47µH MAX1776 toc25 95 EFFICIENCY (%) EFFICIENCY vs.
PAGE 8
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter MAX1776 Pin Description PIN NAME FUNCTION 1 FB 2 GND Ground 3 ILIM Peak Current Control Input. Connect to IN or GND to set peak current limit. ILIM and ILIM2 together set the peak current limit. See Setting Current Limit. 4 LX Inductor Connection. Connect LX to external inductor and diode as shown in Figure 1. 5 IN Input Supply Voltage. Input voltage range is 4.5V to 24V. 6 ILIM2 Peak Current Control Input 2.
PAGE 9
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter MAX1776 MAX1776 D L1 LX CIN D1 OUTPUT COUT OUT Q SHDN R FB S MAXIMUM ON-TIME DELAY ILIM ILIM SET 100mV VSET 1.25V ILIM2 MINIIMUM OFF-TIME DELAY GND Figure 2. Simplified Functional Diagram Input-Output (Dropout) Voltage LX WAVEFORM, CIRCUIT 1 VIN = 15V, ILOAD = 500mA 1A IL 0 10V VLX 0 VOUT 50mV/div 2µs/div Figure 3.
PAGE 10
MAX1776 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter Shutdown (SHDN) A logic low level on SHDN shuts down the MAX1776 converter. When in shutdown, the supply current drops to 3µA to maximize battery life, and the internal P-channel MOSFET turns off to isolate the output from the input. The output capacitance and load current determine the rate at which the output voltage decays. A logic level high on SHDN activates the MAX1776. Do not leave SHDN floating. If unused, connect SHDN to IN.
PAGE 11
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter Maximum Output Current The MAX1776 converter’s output current determines the regulator’s switching frequency. When the converter approaches continuous mode, the output voltage falls out of regulation.
PAGE 12
MAX1776 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter Table 3. Recommended Components CIRCUIT INPUT VOLTAGE (V) MAXIMUM LOAD CURRENT (mA) ILX(PEAK) CURRENT (A) INDUCTOR CAPACITOR 10µH, 1.56A, 70mΩ Toko D75F 646FY-100M, 10µH, 1.70A, 48mΩ Sumida CDRH6D28-100NC, or 10µH, 1.63A, 55mΩ Toko D75C 646CY-100M 0.055 22µH, 1.17A, 120mΩ Toko D75F 646FY-220M, 22µH, 1.09A, 115mΩ Toko D75C 646CY-220M, or 22µH, 1.20A, 95mΩ Sumida CDRH6D28-220NC 100µF, 6.
PAGE 13
24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter board and integrate it into a pseudo-ground plane. When using external feedback, place the resistors as close to the feedback pin as possible to minimize noise coupling. Chip Information TRANSISTOR COUNT: 932 PROCESS: BiCMOS 4X S 8 8 INCHES DIM A A1 A2 b E ÿ 0.50±0.1 H c D e E H 0.6±0.1 L 1 1 α 0.6±0.1 S BOTTOM VIEW D MIN 0.002 0.030 MAX 0.043 0.006 0.037 0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.