ACE4054C

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

VER 1.2

11

ACE4054C

Figure 2. Isolating Capacitive Load on PROG Pin and Filtering

Power Dissipation

The power dissipated in the IC causes the rise of die temperature. Most of the power dissipation is

caused by the internal power MOSFET, and can be calculated by the following equation:

Where PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and

IBAT is the charge current. The approximate ambient temperature at which the thermal feedback begins

to protect the IC is:

Example: An ACE4054C operating from a 5V USB supply is programmed to supply 400mA full-scale

current to a discharged Li-Ion battery with a voltage of 3.75V. Assuming

ΘJA is 150°C /W (see Board

Layout Considerations), the ambient temperature at which the ACE4054C will begin to reduce the charge

current is approximately:

The ACE4054C can be used above 45°C ambient, but the charge current will be reduced from 400mA.

The approximate current at a given ambient temperature can be approximated by:

Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to

approximately:

Moreover, when thermal feedback reduces the charge current, the voltage at the PROG pin is also

reduced proportionally as discussed in the operation section.

It is important to remember that ACE4054C applications do not need to be designed for worst-case

thermal conditions since the IC will automatically reduce power dissipation when the junction temperature

reaches approximately 120°C.