ACE4054

Fully integrated constant current/constant voltage

Li-ion battery charger

VER 1.2

10

Automatic Recharge

After the termination of the charge cycle, the ACE4054 constantly monitors the BAT pin voltage and

starts a new charge cycle when the battery voltage falls below 4.05V, keeping the battery at fully charged

condition. CHRG output enters a strong pull-down state during recharge cycles.

Figure 1. Charge Cycle Diagram

Applications information

Stability Considerations

When a battery is connected to the output, the constant-voltage mode feedback is always stable.

However, in the case of absence of battery, an output capacitor is recommended to reduce ripple voltage.

In the case of high value capacitance or low ESR ceramic capacitors, a small value series resistor (~1Ω)

is recommended. No series resistor is needed if tantalum capacitors are used.

In constant-current mode, the PROG pin is in the feedback loop, thus its impedance affects the stability.

The maximum allowed value of the program resistor is 20K, and additional capacitance reduces this value.

The pole frequency at the PROG pin needs to be kept above 100kHz to maintain device stability.

Therefore, the maximum resistance value can be calculated from the following equation, CPROG is the

capacitance loaded to the PROG pin.