PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

24

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POWER SOURCE

DOK

UOK

PEN1

PEN2

USUS

DC INPUT

CURRENT

LIMIT

USB INPUT

CURRENT

LIMIT

MAXIMUM

CHARGE

CURRENT*

AC-to-DC Adapter at

DC Input

LX

H

X

X

and

L

X

L

L

L

100mA

and

100mA

L

X

L

H

L

500mA

and

500mA

USB Power at DC Input

L

X

L

X

H

Suspend

USB input off,

DC input has

priority

0

H

L

X

L

L

100mA

and

100mA

H

L

X

H

L

500mA

and

500mA

USB Power at USB

Input, DC Unconnected

H

L

X

X

H

Suspend

0

DC and USB

Unconnected

HH

X

X

X

No DC input

No USB input

0

Table 1. Input Limiter Control Logic

*

Charge current cannot exceed the input current limit. Charge can be less than the maximum charge current if the total SYS load

exceeds the input current limit.

X = Don’t care.

Detailed Description

The MAX8671X highly integrated PMIC is ideally suited

for use in portable audio player and handheld applica-

tions. As shown in Figure 2, the MAX8671X integrates

USB power input, AC-to-DC adapter power input (DC),

Li+/Li-Poly battery charger, three step-down regulators,

two linear regulators, and various monitoring and status

outputs. The MAX8671X offers adjustable output volt-

ages for all outputs.

Smart Power Selector

The MAX8671X Smart Power Selector seamlessly dis-

tributes power between the two current-limited external

inputs (USB and DC), the battery (BAT), and the sys-

tem load (SYS). The basic functions performed are:

• With both an external power supply (USB or DC)

and battery (BAT) connected:

When the system load requirements are less than

the input current limit, the battery is charged with

residual power from the input.

When the system load requirements exceed the

input current limit, the battery supplies supple-

mental current to the load through the internal sys-

tem load switch.

• When the battery is connected and there is no exter-

nal power input, the system (SYS) is powered from

the battery.

• When an external power input is connected and

there is no battery, the system (SYS) is powered

from the external power input.

The dual-input Smart Power Selector supports end

products with dual and single external power inputs.

For end products with dual external power inputs, con-

nect these inputs directly to the DC and USB nodes of

the MAX8671X. For end products with a single input,

connect the single input to the DC node and connect

USB to ground or leave it unconnected. In addition to

AC-to-DC adapters current limits, the DC input also

supports USB current limit to allow for end products