LINEAR One Device Replaces Battery Charger, Pushbutton Controller, LED Driver and Voltage Regulator ICs inPortable Electronics Design Note 470 Marty Merchant Owner's Manual - Instructions & User Guide

One Device Replaces Battery Charger, Pushbutton Controller, LED Driver and Voltage Regulator ICs in Portable Electronics Design Note 470 Marty Merchant Introduction Status output indicates when the pushbutton is depressed,

The LTC®3577/LTC3577-1 integrates a number of portable allowing the microprocessor to alter operation or begin device power management functions into one IC, reducing the power-down sequence. Holding the pushbutton down complexity, cost and board area in handheld devices. The for fi ve seconds produces a hard reset. The hard reset major functions include: shuts down the three bucks, the two LDOs and the LED driver, allowing the user to power down the device when

• Five voltage regulators to power memory, I/O, PLL,

the microprocessor is no longer responding.

CODEC, DSP or a touch-screen controller

Battery, USB, Wall and High Voltage Input Sources

• A battery charger and Power Path™ manager

The LTC3577/LTC3577-1 is designed to direct power

• An LED driver for backlighting an LCD display, keypad from two power supply inputs and/or a Li-Ion/Polymer and/or buttons battery. The VBUS input has selectable input current

limit control, designed to deliver 100m A or 500m A for

• Pushbutton control for debouncing the on/off button,

USB applications, or 1A for higher power applications.

supply sequencing and allowing end-users to force a

hard reset when the microcontroller is not responding L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and μModule are registered trademarks of Linear Technology Corporation. Power Path is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective

By combining these functions, the LTC3577/LTC3577-1

owners.

does more than just reduce the number of required ICs; it solves the problems of functional interoperability—where LTC3577/LTC3577-1

otherwise separate features operate together for improved ADAPTER INPUT VOUT

POWER

end-product performance. For instance, when the power

PC USB CC/CV

input is from USB, the limited input current is logically

distributed among the power supply outputs and the POWER ON

SEQUENTIAL BUCK

battery charger.

MICRO VOUT1 MICROCONTROLLER

STATUS

The LTC3577/LTC3577-1 offers other important features, LOGIC

I2C BUS

CONTROL

including Power Path control with instant-on operation, VOUT2 MEMORY

input overvoltage protection for devices that operate in

PUSHBUTTON VOUT3 I/0

harsh environments and adjustable slew rates on the switching supplies, making it possible to reduce EMI

CONTROLLED LCD BACKLIGHTING

while optimizing effi ciency. The LTC3577-1 features a

LED DRIVER

4.1V battery fl oat voltage for improved battery cycle life

and additional high temperature safety margin, while the

CONTROLLED

LTC3577 includes a standard 4.2V battery fl oat voltage LDO1 CODEC/DSP for maximum battery run time.

LDO2 PERIPHERAL POWER

Pushbutton Control

DN470 F01

The built in pushbutton control circuitry of the LTC3577/

Figure 1. Portable Device Power Distribution Block

LTC3577-1 eliminates the need to debounce the pushbut-

Diagram Featuring the LTC3577/LTC3577-1

ton and includes power-up sequence functionality. A PB