8

SL1053

Charge status indication

The SL1053 indicates the status of the charger on the 3-state STAT1 and STAT2 pin. The

following table shows the statuses of this pin.

Condition

STAT1 Pin

STAT2 Pin

In batter charging cycle

High

Low

Charge cycle completed

Low

High

Temperature fault or charge

function disable or output

shorted

High Impedance

High Impedance

Selecting an External PNP Pass-Transistor or P-Channel MOSFET:

The SL1053 drives an external PNP transistor or P-Channel MOSFET to control the charging

current. The specifications must be concerned are the voltage and current rating and package

power dissipation. The external switch is performed as a linear regulator. The maximum power

loss occurs when the constant current regulation starts at the beginning, and it can be calculated

approximately from following equation:

PD(MAX) =I(SNS)×(VDD -0.1V -2.8V)

I(SNS) is the constant regulation current.

The minimum voltage drop between the sense-resistor is 100mV, and the minimum precharge

threshold voltage is 2.8V.

The external pass device with PCB heatsinking must be rated for the maximum power dissipation.

Selecting Input/Output Capacitor

In analog circuit applications, to place a high-frequency decoupling capacitor nearby the controller

IC between input power source and ground is very important. A 0.1uF ceramic is recommended. If

a high ripple and noise input power is chosen, it should have enough capacitance to reduce the

disturbance.

A 0.1uF to 1uF output capacitor is recommended to control the output voltage and keep the output

voltage ripple small when the battery is disconnected