LTC4075 datasheet(9/16 Pages) LINER

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LTC4075/LTC4075X

4075Xfa

The LTC4075 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 LTC4075 has two internal P-channel power MOSFETs

and thermal regulation circuitry. No blocking diodes or

external sense resistors are required.

Power Source Selection

The LTC4075 can charge a battery from either the wall

adapter input or the USB port input. The LTC4075 automati-

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

power sources are present, the LTC4075 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 outputs (

⎯P⎯W⎯RandUSBPWR)

indicate which power source has been selected. Table 1

describes the behavior of these status outputs.

Table 1. Power Source Selection

VUSBIN > 3.95V and

VUSBIN < 3.95V or

VUSBIN > BAT + 50mV

VUSBIN < BAT + 50mV

VDCIN > 4.15V and

Device powered from

VDCIN > BAT + 50mV

wall adapter source;

wall adapter source

USBIN current < 25µA

⎯P⎯W⎯R: LOW

USBPWR: LOW

VDCIN < 4.15V or

Device powered from

No charging

VDCIN < BAT + 50mV

USB source;

⎯P⎯W⎯R: LOW

⎯P⎯W⎯R: Hi-Z

USBPWR: Hi-Z

USBPWR: LOW

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 resis-

tor from the IUSB pin to ground. The program resistor

and the charge current (ICHRG) are calculated using the

following equations:

IDC

CHRG DC

IDC

IUSB

CHRG USB

IUSB

−

1000

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:

ing fromwall adapter

ing fromUSB

ply

BAT

IDC

BAT

IUSB

•

, ( arg

)

•

, ( arg

sup

)

1000

Programming Charge Termination

The charge cycle terminates when the charge current falls

below the programmed termination threshold during con-

stant-voltage mode. This threshold is set by connecting an

external resistor, RITERM, from the ITERM pin to ground.

The charge termination current threshold (ITERMINATE) is

set by the following equation:

ITERM

TERMINATE

ITERM

100

OPERATIO

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