ltc4069edc-4.4 Linear Technology Corporation, ltc4069edc-4.4 Datasheet - Page 10

• Manufacturer Part Number: ltc4069edc-4.4
• Description: Standalone 750ma Li-ion Battery Charger In 2 ? 2 Dfn With Ntc Thermistor Input
• Manufacturer: Linear Technology Corporation

OPERATIO
constant-voltage mode straight from constant-tempera-
ture mode. Regardless of mode, the voltage at the PROG
pin is proportional to the current delivered to the battery.
Battery Temperature Monitoring via NTC
The battery temperature is measured by placing a negative
temperature coefficient (NTC) thermistor close to the
battery pack. The NTC circuitry is shown in Figure 3.
To use this feature, connect the NTC thermistor, R
between the NTC pin and ground and a resistor, R
from the NTC pin to V
with a value equal to the value of the chosen NTC ther-
mistor at 25°C (this value is 10k for a Vishay
NTHS0603NO1N1002J thermistor). The LTC4069-4.4 goes
into hold mode when the value of the NTC thermistor drops
LTC4069-4.4
10
POWER
U
ON
CC
1/4 CHARGE CYCLE
. R
(1.125 HOURS)
NOM
1/10 FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
IS V
NO CHARGE CURRENT
CHRG PULSES (2Hz)
V
TRICKLE CHARGE MODE
CC
BAT
DEFECTIVE BATTERY
BAD BATTERY MODE
< 3V
should be a 1% resistor
< 2.9V?
Figure 2. State Diagram of LTC4069-4.4 Operation
V
YES
TEMPERATURE
BAT
≤ 2.9V
TEMPERATURE NOT OK
NOT OK
NO
1/2 CHARGE CYCLE
NOM
NTC
CHARGE CYCLE
(2.25 HOURS)
BATTERY CHARGING SUSPENDED
CHRG PULSES (2Hz)
(4.5 HOURS)
IF V
V
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
IS V
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
,
,
CC
CC
BAT
> V
FAST CHARGE MODE
RECHARGE MODE
> 3.6V AND
BAT
< 4.3V?
to 0.53 times the value of R
approximately 40°C, and when the value of the NTC
thermistor increases to 3.26 times the value of R
which corresponds to approximately 0°C. Hold mode
freezes the timer and stops the charge cycle until the
thermistor indicates a return to a valid temperature. For a
Vishay NTHS0603NO1N1002J thermistor, this value is
32.6k which corresponds to approximately 0°C. The hot
and cold comparators each have approximately 3°C of
hysteresis to prevent oscillation about the trip point.
When the charger is in Hold mode (battery temperature is
either too hot or too cold) the CHRG pin pulses in a 2Hz,
25% duty cycle frequency unless the charge task is
finished or the battery is assumed to be defective. If the
NTC pin is grounded, the NTC function will be disabled.
NTC FAULT
RECHARGE
+ 80mV?
UVLO
TEMPERATURE OK
2.9V < V
YES
YES
BAT
< 4.3V
NO
NO
CHRG HIGH IMPEDANCE
NO CHARGE CURRENT
CHRG HIGH IMPEDANCE
STANDBY MODE
UVLO MODE
NOM
V
, which corresponds to
BAT
> 4.3V
4069 F02
406944f
NOM
,