LTC4078XEDD-PBF 查看數據表（PDF） - Linear Technology

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LTC4078XEDD-PBF

Dual Input Li-Ion Battery Charger with Overvoltage Protection

Linear Technology 

LTC4078/LTC4078X

PIN FUNCTIONS

USBIN (Pin 1): USB Input Supply Pin. This input provides

power to the battery charger assuming a voltage greater

than VUVUSB and less than VOVUSB is present (typically

3.95V to 6V respectively). However, the DCIN input will

take priority if a voltage greater than VUVDC is present at

DCIN (typically 4.15V). The USBIN input allows charge

currents up to 850mA. This pin should be bypassed with

a 1μF capacitor.

IUSB (Pin 2): Charge Current Program for USB Power.

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:

IBAT

=

VIUSB

RIUSB

• 1000

ITERM (Pin 3): Termination Current Threshold Program.

The termination current threshold, ITERMINATE, is set by

connecting a resistor, RITERM, to ground. ITERMINATE is set

by the following formula:

ITERMINATE

=

100V

RITERM

When the battery current, IBAT, falls below the termination

threshold, charging stops and the CHRG output becomes

high impedance. This pin is internally clamped to approxi-

mately 1.5V. Driving this pin to voltages beyond the clamp

voltage should be avoided.

PWR (Pin 4): Open-Drain Power Supply Status Output.

When the DCIN or USBIN pin voltage is valid to begin charg-

ing (i.e. when the supply is greater than the undervoltage

lockout threshold, less than the overvoltage lockout thresh-

old and at least 120mV above the battery terminal), the

PWR pin is pulled low by an internal N-channel MOSFET.

Otherwise PWR is high impedance. This output is capable

of driving an LED.

CHRG (Pin 5): Open-Drain Charge Status Output. When the

LTC4078/LTC4078X are charging, the CHRG pin is pulled

low by an internal N-channel MOSFET. When the charge

cycle is completed, CHRG becomes high impedance. This

output is capable of driving an LED.

ENABLE (Pin 6): Enable Input. When the LTC4078/LTC4078X

are charging from the DCIN source, a logic low on this

pin enables the charger. When the LTC4078/LTC4078X are

charging from the USBIN source, a logic high on this pin

enables the charger. If this input is left floating, an internal

2MΩ pulldown resistor defaults the LTC4078/LTC4078X

to charge when a wall adapter is applied and to shut down

if only the USB source is applied.

BATDET (Pin 7): Battery Detection Input. When the volt-

age on this pin falls below VBDET (typically 1.75V), the

charger is on and ready for charging a battery. If this

input is left floating, an internal pull-up resistor will dis-

able charging.

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:

IBAT

=

VIDC

RIDC

• 1000

BAT (Pin 9): Battery 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. This input

provides power to the battery charger assuming a voltage

greater than VUVDC and less than VOVDC is present (typi-

cally 4.15V to 6V respectively). A valid voltage on the DCIN

input will always take priority over the USBIN input. The

DCIN input allows charge currents up to 950mA. This pin

should be bypassed with a 1μF capacitor.

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

package is ground and must be soldered to PC board ground

for electrical connection and maximum heat transfer.

4078xfb

7

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