ACE4054

Fully integrated constant current/constant voltage

Li-ion battery charger

VER 1.4

10

ACE4054 has a self‐temperature‐limiting (STL) function, the chip starts to limit its charge current by

reducing VPROG gradually after silicon temperature rises above 70℃. Say if the difference of junction

and ambient temperature is 45℃ at certain power rating, ACE4054 would have the same charge current

and junction temperature as chips without STL function at room temperature. As the ambient temperature

rises up to 55℃, a chip without STL would have 100℃ of junction temperature, while ACE4054 would

reduce its charge current and hence the junction temperature would be much lower. The STL function

helps to improve system reliability.

Charge Termination

The ACE4054 keeps monitoring the PROG pin during the charging process. It terminates the charge

cycle when the charge current falls to 1/10th the programmed value after the final float voltage is reached.

When the PROG pin voltage falls below 100mV for longer than tTERM (typically 1ms), charging is

terminated. The charge current is latched off and the ACE4054 enters standby mode, where the input

supply current drops to 200

μA. (Note: C/10 termination is disabled in trickle charging and thermal limiting

modes).

During charging, the transient response of the circuit can cause the PROG pin to fall below 100mV

temporarily before the battery is fully charged, thus can cause a premature termination of the charge

cycle. A 1ms filter time (tTERM) on the termination comparator can prevent this from happening. Once the

average charge current drops below 1/10th the programmed value, the ACE4054 terminates the charge

cycle and ceases to provide any current through the BAT pin. In this state, all loads on the BAT pin must

be supplied by the battery.

Figure 1. Charge Cycle Diagram