LTC4062

14

4062f

APPLICATIO S I FOR ATIO

comparator ensures that transient loads of this nature do

not result in premature charge cycle termination. Once the

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

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

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

CHRG STATE: Hi-Z

CHRG STATE: PULL-DOWN

POWER ON

EN = 0V

OR UVLO

CONDITION

STOPS

CHRG STATE:

Figure 5. State Diagram of a Charge Cycle Using User-Selectable Termination