UB10803

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

5 of 10

www.unisonic.com.tw

QW-R502-A26.a



OPERATION

The UTC UB10803 charges a single-cell Li-ion/Polymer battery with a programmed constant current (CC) or a

battery voltage is deeply discharged to lower than 2.75V, The UTC UB10803 pre-charges the battery with a 20%

programmable current until the battery voltage rises above the pre-charge threshold. After pre-charge finishes,

constant-current (CC) charging mode begins with the pre-set fast charge current. Normally, the battery voltage rises

gradually during CC charge phase. When the battery voltage reaches nearly 4.2V, the charger enters the

constant-voltage (CV) charging mode and begins to regulate the battery voltage at 4.2V while diminishing the

charging current gradually. When the charging current is reduced to an amount smaller than the programmed

End-Of-Charge (EOC) current level, the charger gives out a “full-charge” indication through the CHG pin, but the

charger still continues to regulate the battery voltage at 4.2V with safe & small current.

signal turns to LOW when pre-charge starts and rises to HIGH when EOC is reached. After reaching EOC, the

after EOC can be caused by a load connected to the battery.

charge current accordingly to maintain the temperature from increasing furthermore. This is an important function to

achieve safe operation even when the printed circuit board (PCB) is not effective in leaking out the heat generated

by the linear charger.

1. PPR Indication

The PPR pin is implemented as an open-drain output to provide a power-good indication of the input power source

such as an AC adapter. When the input voltage is higher than the POR (Power-On Reset) threshold, the PPR pin

turns on the internal open-drain MOSFET to indicate logic LOW signal. The PPR indication is designed to be

independent on the chip enable (EN-pin) input. When the internal open-drain FET is turned off, the PPR pin should

leak less than 1μA current. When turned on, the PPR pin should be able to sink at least 5mA current under all

operating conditions. The PPR pin can be used to drive an LED or worked as logic interface to a microprocessor.

2. Power-Good Range

The input voltage is considered as power good when it meets the following three conditions:

activities are disabled when the input voltage falls out of the power-good range.

3. Input and Output Comparator

Obviously, when the input source voltage is lower than the battery voltage, no charging activity could be started

and the charger will disable the internal pass element to prevent battery leakage. Charge begins when the input

charger is completely turned off when the input power is removed from the charger.

4. CHG Indication

The CHG pin is implemented as an open-drain output to give a logic LOW when a charge cycle begins and turn

HIGH when an end-of-charge (EOC) condition is reached. This pin is designed with a sinking ability of more than

5mA so as to drive an LED. When the charger is disabled through EN-pin, the CHG output is high impedance. The

CHG pin can also be used to interface with a microprocessor.

5. EN Input

The chip is enabled by a logic LOW signal applied to the EN pin. This pin is realized with a 200kΩ internal

pull-down resistor such that even the EN pin is left floating, the input is equivalent to logic LOW and the chip is

enabled by default. Similarly, the chip is disabled when the EN pin receives a logic HIGH signal.