UB10803

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

7 of 10

www.unisonic.com.tw

QW-R502-A26.a



APPLICATION INFORMATION

Input Capacitor Selection

The input capacitor is employed to decouple the power supply from load transients and suppress noise from

and GND pin to stabilize the operation during the start up, especially when the input supply is passing the POR

hysteresis to provide sufficient guard band from noise or load transient to trigger the system to reset.

Output Capacitor Selection

The criterion for selecting the output capacitor is to maintain the stability of the charger as well as to bypass any

transient load current. Typically, a minimum capacitance of 1μF X5R ceramic capacitor is recommended and

sufficient for stabilizing the system. For systems that may happen to occasionally see high load transients, the output

capacitor may be increased to further bypass any ripples so caused.

Charge Current Limit

calculated in previous formula. However, the actual charge current in the CC mode could also be limited by other

pass element may limit the amount of current that passes through it.

When the input voltage is sufficiently higher than the battery voltage, yet has not increased the die temperature

over the thermal limit.

When the input voltage is reduced (or the battery voltage increases towards the input voltage), the charge current

is limited by the on-resistance of the pass element. Therefore, it is recommended to employ sufficiently high input

voltage for applications that require constant charging current over the entire charging period. But for applications

that needs to minimize the heat dissipation, a current-limiting adapter maybe applied to maintain constant charging

current at whole charging phase.

In addition, if the input voltage increases, the charge current may also be reduced due to the thermal fold back

function. The high voltage drop across the pass element increases the power dissipation therein and thus causing

the die temperature to increase significantly.

Layout Guidance

The UTC UB10803 employs thermally-enhanced DFN package, which has an exposed thermal pad at its bottom

side. It is recommended to connect as much copper as possible between the exposed pad and PCB to make it

effective in taking the heat away from the die. For applications requiring high charging current, the thermal

impedance should be further reduced by employing more layers of copper to connect with the exposed pad through

thermal via.

Input Power Sources

The UTC UB10803 works with different types of AC/DC adapter or USB port (any type) with no special

requirements. The UTC UB10803 accepts input voltage ranges from 4.5V to 6.5V for normal operation.