LTC4077EDD(RevA) 查看數據表（PDF） - Linear Technology

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LTC4077EDD
(Rev.:RevA)

Dual Input Standalone Li-Ion Battery Charger

Linear Technology 

OPERATIOU

The LTC4077 is designed to efficiently manage charging of

a single-cell lithium-ion battery from two separate power

sources: a wall adapter and USB power bus. Using the

constant-current/constant-voltage algorithm, the charger

can deliver up to 950mA of charge current from the wall

adapter supply or up to 650mA of charge current from the

USB supply with a final float voltage accuracy of ±0.6%.

The LTC4077 has two internal P-channel power MOSFETs

and thermal regulation circuitry. No blocking diodes or

external sense resistors are required.

Power Source Selection

The LTC4077 can charge a battery from either the wall

adapter input or the USB port input. The LTC4077 automati-

cally senses the presence of voltage at each input. If both

power sources are present, the LTC4077 defaults to the

wall adapter source provided sufficient power is present

at the DCIN input. “Sufficient power” is defined as:

• Supply voltage is greater than the UVLO threshold.

• Supply voltage is greater than the battery voltage by

50mV (180mV rising, 50mV falling).

The open drain power status output (PWR) indicates that

sufficient power is available. Table 1 describes the behavior

of this status output.

Table 1. Power Source Selection

VDCIN > 4.15V and

VDCIN > BAT + 50mV

VUSBIN > 3.95V and

VUSBIN > BAT + 50mV

Device powered from

wall adapter source;

USBIN current < 25µA

PWR: LOW

VDCIN < 4.15V or

VDCIN < BAT + 50mV

Device powered from

USB source;

PWR: LOW

VUSBIN < 3.95V or

VUSBIN < BAT + 50mV

Device powered from

wall adapter source

PWR: LOW

No charging

PWR: Hi-Z

LTC4077

Programming and Monitoring Charge Current

The charge current delivered to the battery from the wall

adapter supply is programmed using a single resistor from

the IDC pin to ground. Likewise, the charge current from

the USB supply is programmed using a single resistor

from the IUSB pin to ground if HPWR is set on its high

logic state or from the IUSBL pin to ground if HPWR is

set on its low logic state or it is left floating. The program

resistor and the charge current (ICHRG) are calculated

using the following equations:

RIDC

=

1000V

ICHRG(DC)

,

ICHRG(DC)

=

1000V

RIDC

RIUSB

=

1000V

ICHRG(USB)

,

ICHRG(USB)

=

1000V

RIUSB

RIUSBL

=

200V

ICHRG(USB)

,

ICHRG(USB)

=

200V

RIUSBL

Charge current out of the BAT pin can be determined at

any time by monitoring the IDC or IUSB pin voltage and

using the following equations:

IBAT

=

VIDC

RIDC

• 1000, (charging

from

wall

adapter)

IBAT

=

VIUSB

RIUSB

• 1000,

(charging

HPWR =

from

high)

USB

supply,

IBAT

=

VIUSBL

RIUSBL

• 200,

(charging from

HPWR = low)

USB

supply,

4077fa

9

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