Datasheet

LTC4062
14
4062fb
APPLICATIO S I FOR ATIO
WUUU
threshold. The 1.5ms filter time (t
TERM
) on the internal
comparator ensures that transient loads of this nature do
not result in premature charge cycle termination. Once the
average charge current drops below I
DETECT
, the charger
terminates the charge cycle.
The CHRG output is in a pull-down state while charging
and in a high impedance state once charging has stopped.
Figure 4 describes the operation of the LTC4062 charger
when charge current termination is used.
When the charger is set for charge current termination and
the battery is removed from the charger, a sawtooth
waveform of several hundred mV will appear at the charger
output. This is caused by the repeated cycling between
termination and recharge events. This cycling results in
pulsing at the CHRG output. If an LED is connected to this
pin, it will exhibit a pulsing pattern, indicating to the user
that a battery is not present. The frequency of the sawtooth
is dependent on the amount of output capacitance.
Figure 4. State Diagram of a Charge Cycle Using Charge Current Termination
CHARGE MODE
FULL CURRENT
I
BAT
< I
DETECT
IN VOLTAGE MODE
4062 F04
TRICKLE CHARGE MODE
1/10TH FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT < 4.1V
BAT > 4.1V
BAT < 4.1V
EN = 5V
OR
UVLO CONDITION
STANDBY MODE
NO CHARGE CURRENT
CHRG STATE: Hi-Z
SHUTDOWN MODE
I
CC
DROPS TO 20µA
CHRG STATE: Hi-Z
CHRG STATE: PULL-DOWN
CHRG STATE: PULL-DOWN
POWER ON
EN = 0V
OR UVLO
CONDITION
STOPS
CHARGE MODE
FULL CURRENT
4062 F05
TRICKLE CHARGE MODE
1/10TH FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT
EN = 5V
OR
UVLO CONDITION
SHUTDOWN MODE
I
CC
DROPS TO 20µA
CHRG STATE: Hi-Z
CHRG STATE: PULL-DOWN
POWER ON
EN = 0V
OR UVLO
CONDITION
STOPS
CHRG STATE:
PULL-DOWN IF I
BAT
> I
DETECT
Hi-Z IF I
BAT
< I
DETECT
Figure 5. State Diagram of a Charge Cycle Using User-Selectable Termination