LTC4063 LINER [Linear Technology], LTC4063 Datasheet - Page 9

• Manufacturer Part Number: LTC4063
• Description: Standalone Linear Li-Ion Charger with Micropower Low Dropout Linear Regulator
• Manufacturer: LINER [Linear Technology]

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 V
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 V
nation, allowing external charge termination to be used by
the CHGEN input. See Applications Information for more
on charge termination methods.
U
CC
disables internal termi-
CC
pin
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:
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:
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
I
R
BAT
PROG
=
R
=
V
PROG
PROG
1000
I
CHG
• 1000
V
,
I
CHG
=
1000
R
PROG
V
LTC4063
4063fb
9