LTC3577EUFF-3(RevA) Ver la hoja de datos (PDF) - Linear Technology

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Fabricante

LTC3577EUFF-3
(Rev.:RevA)

Highly Integrated Portable Product PMIC

Linear Technology 

LTC3577-3/LTC3577-4

OPERATION

PowerPath OPERATION

Introduction

The LTC3577-3/LTC3577-4 are highly integrated power

management IC that includes the following features:

– PowerPath controller

– Battery charger

– Ideal diode

– Input overvoltage protection

– Pushbutton controller

– Three step-down switching regulators

– Two low dropout linear regulators

– 40V LED backlight controller

Designed specifically for USB applications, the PowerPath

controller incorporates a precision input current limit

which communicates with the battery charger to ensure

that input current does not violate the USB average input

current specification. The ideal diode from BAT to VOUT

guarantees that ample power is always available to VOUT

even if there is insufficient or absent power at VBUS. The

LTC3577-3/LTC3577-4 also have the ability to receive

power from a wall adapter or other non-current-limited

power source. Such a power supply can be connected

to the VOUT pin of the LTC3577-3/LTC3577-4 through an

external device such as a power Schottky or FET as shown

in Figure 1. The LTC3577-3/LTC3577-4 have the unique

ability to use the output, which is powered by an external

supply, to charge the battery while providing power to

the load. A comparator on the WALL pin is configured to

detect the presence of the wall adapter and shut off the

connection to the USB. This prevents reverse conduction

from VOUT to VBUS when a wall adapter is present.

The LTC3577-3/LTC3577-4 also include a pushbutton

input to control the power sequencing of two synchronous

step-down switching regulators (Buck1 and Buck2), a low

dropout regulator (LDO2) and system reset. The three

FROM AC ADAPTER

4.3V

(RISING)

–

3.2V

(FALLING)

+

WALL

4

+

–

FROM

USB

VBUS

40

+–

75mV (RISING)

25mV (FALLING)

ENABLE

USB CURRENT LIMIT

VOUT

ACPR

41

VOUT

39

CONSTANT-CURRENT

CONSTANT-VOLTAGE

BATTERY CHARGER

IDEAL

DIODE

+

–

+– 15mV

IDGATE

37

SYSTEM

LOAD

OPTIONAL

EXTERNAL

IDEAL DIODE

PMOS

20

BAT

Figure 1. Simplified PowerPath Block Diagram

BAT

38

357734 F01

+

Li-Ion

357734fa

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