LTC4090(RevA) 데이터 시트보기 (PDF) - Linear Technology

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LTC4090
(Rev.:RevA)

USB Power Manager with 2A High Voltage Bat-Track Buck Regulator

Linear Technology 

LTC4090/LTC4090-5

OPERATION

Introduction

The LTC4090/LTC4090-5 are complete PowerPathTM

controllers for battery powered USB applications. The

LTC4090/LTC4090-5 are designed to receive power from

a low voltage source (e.g., USB or 5V wall adapter), a

high voltage source (e.g., FireWire/IEEE1394, automotive

battery, 12V wall adapter, etc.), and a single-cell Li-Ion

battery. They can then deliver power to an application

connected to the OUT pin and a battery connected to the

BAT pin (assuming that an external supply other than

the battery is present). Power supplies that have limited

current resources (such as USB VBUS supplies) should

be connected to the IN pin which has a programmable

current limit. Battery charge current will be adjusted to

ensure that the sum of the charge current and load cur-

rent does not exceed the programmed input current limit

(see Figure 1).

An ideal diode function provides power from the battery

when output / load current exceeds the input current limit or

when input power is removed. Powering the load through

the ideal diode instead of connecting the load directly to

the battery allows a fully charged battery to remain fully

charged until external power is removed. Once external

power is removed the output drops until the ideal diode is

forward biased. The forward biased ideal diode will then

provide the output power to the load from the battery.

The LTC4090/LTC4090-5 also include a high voltage

switching regulator which has the ability to receive power

from a high voltage input. This input takes priority over the

USB VBUS input (i.e., if both HVIN and IN are present, load

current and charge current will be delivered via the high

voltage path). When enabled, the high voltage regulator

regulates the HVOUT voltage using a constant frequency,

current mode regulator. An external PFET between HVOUT

(drain) and OUT (source) is turned on via the ⎯H⎯V⎯P⎯R pin

allowing OUT to charge the battery and/or supply power

to the application. The LTC4090’s Bat-Track maintains

approximately 300mV between the OUT pin and the BAT

pin, while the LTC4090-5 provides a fixed 5V output.

PowerPath is a trademark of Linear Technology Corporation

HVIN

Q1

HIGH VOLTAGE

BUCK REGULATOR

+

4.25V (RISING)

3.15V (FALLING)

–

+

–

SW

L1

D1

HVOUT

C1

HVPR

19

12

IN

ENABLE

75mV (RISING)

+– 25mV (FALLING)

OUT

USB CURRENT LIMIT

CC/CV REGULATOR

CHARGER

30mV

IDEAL

DIODE

BAT

OUT

21

LOAD

30mV

+

EDA

–

GATE

21

BAT

21

4090 F01

+

Li-Ion

Figure 1. Simplified PowerPath Block Diagram

4090fa

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