LTC4077 datasheet(7/16 Pages) LINER

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LTC4077

4077fa

USBIN (Pin 1): USB Input Supply Pin. Provides power to

thebatterycharger.Themaximumsupplycurrentis650mA.

This pin should be bypassed with a 1µF capacitor.

IUSB(Pin2):ChargeCurrentProgramforHighUSBPower.

The charge current is set by connecting a resistor, RIUSB,

to ground. When charging in constant-current mode, this

pin servos to 1V. The voltage on this pin can be used to

measure the battery current delivered from the USB input

using the following formula:

BAT

IUSB

•1000

IUSBL(Pin3):ChargeCurrentProgramforLowUSBPower.

The charge current is set by connecting a resistor, RIUSBL,

to ground. When charging in constant current mode, this

pin servos to 0.2V. The voltage on this pin can be used to

measure the battery current delivered from the USB input

using the following formula:

BAT

IUSBL

•200



PWR (Pin 4): Open-Drain Power Supply Status Output.

When the DCIN or USBIN pin voltage is sufﬁcient to begin

charging (i.e. when the supply is greater than the under-

voltage lockout threshold and at least 180mV above the

battery terminal), the PWR pin is pulled low by an internal

N-channel MOSFET. Otherwise PWR is high impedance.

This output is capable of sinking up to 10mA, making it

suitable for driving an LED.



CHRG (Pin 5): Open-Drain Charge Status Output. When

the LTC4077 is charging, the CHRG pin is pulled low by

an internal N-channel MOSFET. When the charge cycle is

completed, CHRG becomes high impedance. This output

is capable of sinking up to 10mA, making it suitable for

driving an LED.



EN (Pin 6): Charge Enable Input. A logic low on this pin

enables the charger. If left ﬂoating, an internal 2MΩ pull-

down resistor defaults the LTC4077 to charge mode. Pull

this pin high for shutdown.

HPWR (Pin 7): HPWR Enable Input. Used to control the

amount of current drawn from the USB port. A logic high

on the HPWR pin sets the current limit at the current

programmed by the IUSB pin. A logic low on the HPWR

pin sets the current limit at the current programmed by the

IUSBL pin. An internal 2MΩ pull-down resistor defaults

the HPWR pin to its low current state.

IDC (Pin 8): Charge Current Program for Wall Adapter

Power. The charge current is set by connecting a resis-

tor, RIDC, to ground. When charging in constant-current

mode, this pin servos to 1V. The voltage on this pin can

be used to measure the battery current delivered from the

DC input using the following formula:

BAT

IDC

• 1000

BAT (Pin 9): Charger Output. This pin provides charge

current to the battery and regulates the ﬁnal ﬂoat voltage

to 4.2V.

DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides

power to the battery charger. The maximum supply

current is 950mA. This should be bypassed with a 1μF

capacitor.

Exposed Pad (Pin 11): GND. The exposed backside of the

packageisgroundandmustbesolderedtoPCboardground

for electrical connection and maximum heat transfer.

PI FU CTIO S

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