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LTC4063

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OPERATIO

The LTC4063 is designed to charge a single cell lithium-

ion battery and supply a regulated output voltage for bat-

tery-powered applications. Using the constant current/con-

stant voltage algorithm, the charger can deliver up to 1A of

charge current with a final float voltage accuracy of

±0.35%.

The LTC4063 includes an internal P-channel power

MOSFET and thermal regulation circuitry. No blocking diode

or external sense resistor is required; thus, the basic charger

circuit requires only two external components.

The LDO regulator is powered from the battery terminal

and can be programmed for output voltages between

1.2V and 4.2V using external resistors. An output capaci-

tor is required on the OUT pin for stability and improved

transient response. A low ESR capacitor of

≥2µF should

be used.

Normal Operation

The charge cycle begins when the voltage at the VCC pin

rises above the UVLO level and a discharged battery is

connected to BAT. If the BAT pin voltage is below 2.9V, the

charger enters trickle charge mode. In this mode, the

LTC4063 supplies 1/10th of the programmed charge

current in order to bring the battery voltage up to a safe

level for full current charging.

Once the BAT pin voltage rises above 2.9V, the charger

enters constant-current mode where the programmed

charge current is supplied to the battery. When the BAT pin

approaches the final float voltage (4.2V), the LTC4063

enters constant-voltage mode and the charge current

decreases as the battery becomes fully charged.

The LTC4063 offers several methods with which to termi-

nate a charge cycle. Connecting an external capacitor to

the TIMER pin activates an internal timer that stops the

charge cycle after the programmed time period has

elapsed. Grounding the TIMER pin and connecting a

resistor to the IDET pin causes the charge cycle to

terminate once the charge current falls below a set

threshold when the charger is in constant-voltage mode.

Connecting the TIMER pin to VCC disables internal termi-

nation, allowing external charge termination to be used by

the CHGEN input. See Applications Information for more

on charge termination methods.

Programming the Charge Current

The charge current is programmed using a single resistor

from the PROG pin to ground. The battery charge current

is 1000 times the current out of the PROG pin. The

program resistor and the charge current are calculated by

the following equations:

PROG

CHG

PROG

1000

The charge current out of the BAT pin can be determined

at any time by monitoring the PROG pin voltage and

applying the following equation:

BAT

PROG

• 1000

SmartStart

When the LTC4063 is initially powered on or brought out

of shutdown mode, the charger checks the voltage on

BAT. If the BAT pin is below the recharge threshold of 4.1V

(which corresponds to approximately 80% to 90% battery

capacity), the LTC4063 enters charge mode and begins a

full charge cycle. If the BAT pin is above 4.1V, the LTC4063

enters standby mode and does not begin charging. This

feature reduces the number of unnecessary charge cycles,

prolonging battery life.

Automatic Recharge

When the charger is in standby mode, the LTC4063

continuously monitors the voltage on the BAT pin. When

the BAT pin voltage drops below 4.1V, the charge cycle is

automatically restarted and the internal timer is reset to

50% the programmed charge time (if time termination is

being used). This feature eliminates the need for periodic

charge cycle initiations and ensures that the battery is

always fully charged. Automatic recharge is disabled in

User Termination mode.

Thermal Regulation

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise

above a preset value of approximately 105

°C. This feature

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