ACE4054C

500mA/1.5A Standalone Linear Li-Ion Battery Charge

VER 1.2

10

Thermal Limiting

Build-in feedback circuitry mechanism can reduce the value of the programmed charge current once the

die temperature tends to rise above 120°C, hence prevents the temperature from further increase and

ensure device safe operation.

Undervoltage Lockout (UVLO)

Build-in undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode

until VCC rises above the undervoltage lockout threshold. The UVLO circuit has a built-in hysteresis of

200mV. Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps

the charger in shutdown mode if VCC falls to within 30mV of the battery voltage. If the UVLO comparator

is tripped, the charger will not come out of shutdown mode until VCC rises 100mV above the battery

voltage.

Manual Shutdown

Floating the PROG pin by removing the resistor from PROG pin to ground can put the device in

shutdown mode. The battery drain current is thus reduced to less than 5μA and the supply current to less

than 50μA. Reconnecting the resistor back will restart a new charge cycle.

The CHRG pin is in a high impedance state if the ACE4054C is in undervoltage lockout mode.

Automatic Recharge

After the termination of the charge cycle, the ACE4054C 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 pull-down state during recharge cycles.

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 (~1

Ω

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

Average rather than instantaneous charge current is more of a concern. A simple low pass filter can be

used on the PROG pin to measure the average battery current as shown in Figure 2. A 10K resistor has

been added between the PROG pin and the filter capacitor to ensure stability.