Automatic recharge

AN2370

10/14

6

Automatic recharge

Once the charge cycle is terminated, the STC4054 continuously monitors the voltage on the

when the battery voltage falls below 4.05 V (which corresponds to approximately 80% to

90% battery capacity).

This ensures that the battery is kept at or near a fully charged condition and eliminates the

need for periodic charge cycle initiations. CHRG output enters a strong pulldown state

during recharge cycles.

Figure 9.

State diagram of a typical charge cycle

TRICKLE CHARGE

MODE

1/10TH FULL

CURRENT

CHRG: STRONG

PULL-DOWN

CHARGE MODE

FULL CURRENT

CHRG: STRONG

PULL-DOWN

STANDBY MODE

NO CHARGE

CURRENT

CHRG: WEAK

PULL-DOWN

POWER ON

Bat >2.9V

Prog<100mV

2.9V<Vbat<4.05V

Bat >2.9V

Bat <2.9V

SHUTDOWN MODE

CHRG: Hi-Z IN UVLO

WEAK PULL-DOWN

OTHERWISE

ICC DROPS TO <25µA

PROG

RECONNECTED

OR

UVLO

CONDITION

STOPS

PROG FLOATED

OR

UVLO

CONDITION