6

SL1053

Detection

First, the FB/CE pin must connect to VDD or a voltage divider to enable the charge function. And

then if a battery is already inserted and the input power source is absent, the SL1053 will enter

sleep mode to prevent draining power from battery. When input power source and battery are both

existed, another detection is the battery temperature. The TS pin voltage must be in the allowed

range as shown in Figure 6 and the electrical characteristics, and then the SL1053 will start the

charge cycle according to the battery voltage conditions.

Precharge Mode

When the battery voltage is lower than the precharge threshold VO(MIN), the SL1053 begins to

charge the battery in precharge mode. In this condition, the precharge current is set at

approximately 10% of the constant regulation current. The purposes of small precharge current are

to minimize the power dissipation on the external switch during the precharge period and to revive

deeply discharged battery cells.

Constant Current Regulation Charge Mode

When the battery voltage is between the precharge threshold VO(MIN) and the regulation voltage

VO(REG), the SL1053 starts the constant current regulation charge mode. SL1053 monitors

charge current with voltage drop between two terminals of a sense-resistor, RCS, which connects

to pin VDD and CS. The following equation can calculate the desired charging current.