LTC4080X datasheet(9/20 Pages) LINER

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LTC4080X

4080Xf

PI FU CTIO S

BAT (Pin 1): Charge Current Output and Buck Regulator

Input. Provides charge current to the battery and regulates

the ﬁnal ﬂoat voltage to 4.2V. An internal precision resistor

divider from this pin sets the ﬂoat voltage and is disconnected

in charger shutdown mode. This pin must be decoupled

with a low ESR capacitor for low-noise buck operation.

VCC(Pin2):PositiveInputSupplyVoltage.Thispinprovides

power to the battery charger. VCC can range from 3.75V

to 5.5V. This pin should be bypassed with at least a 1µF

capacitor. When VCC is less than 32mV above the BAT pin

voltage, the battery charger enters shutdown mode.

⎯E⎯N⎯_⎯C⎯H⎯R⎯G (Pin 3): Enable Input Pin for the Battery Charger.

Pulling this pin above the manual shutdown threshold (VIH)

puts the LTC4080X charger in shutdown mode, thus stop-

ping the charge cycle. In battery charger shutdown mode,

the LTC4080X has less than 10µA supply current and less

than 5µA battery drain current provided the regulator is

not running. Enable is the default state, but the pin should

be tied to GND if unused.

PROG (Pin 4): Charge Current Program and Charge Cur-

rent Monitor Pin. Connecting a 1% resistor, RPROG, to

ground programs the charge current. When charging in

constant-current mode, this pin servos to 1V. In all modes,

the voltage on this pin can be used to measure the charge

current using the following formula:

BAT

PROG

•40 0

⎯A⎯C⎯P⎯R (Pin 5): Open-Drain Power Supply Status Out-

put. When VCC is greater than the undervoltage lockout

threshold (3.6V) and greater than VBAT + 82mV, the ⎯A⎯C⎯P⎯R

pin will be pulled to ground; otherwise the pin is high

impedance.

⎯C⎯H⎯R⎯G (Pin 6): Open-Drain Charge Status Output. The

charge status indicator pin has three states: pulldown,

high impedance state, and pulsing at 2Hz. This output can

be used as a logic interface or as an LED driver. When the

battery is being charged, the

⎯C⎯H⎯R⎯G pin is pulled low by an

internal N-channel MOSFET. When the charge current drops

to 10% of the full-scale current, the

⎯C⎯H⎯R⎯G pin is forced to

a high impedance state. When the battery voltage remains

below 2.9V for one quarter of the full charge time, the

battery is considered defective, and the

⎯C⎯H⎯R⎯G pin pulses

at a frequency of 2Hz with 75% duty cycle.

FB (Pin 7): Feedback Pin for the Buck Regulator. A resistor

divider from the regulator’s output to the FB pin programs

the output voltage. Servo value for this pin is 0.8V.

MODE (Pin 8): Burst Mode Enable Pin. Tie this pin high to

force the LTC4080X regulator into Burst Mode operation

for all load conditions. Tie this pin low to force constant-

frequency mode operation for all load conditions. Do not

ﬂoat this pin.

EN_BUCK (Pin 9): Enable Input Pin for the Buck Regulator.

Pull this pin high to enable the regulator, pull low to shut

down. Do not ﬂoat this pin.

SW (Pin 10): Switch Pin for the Buck Regulator. Minimize

the length of the metal trace connected to this pin. Place

the inductor as close to this pin as possible.

GND (Pin 11): Ground. This pin is the back of the Exposed

Pad package and must be soldered to the PCB for electrical

connection and rated thermal performance.

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