ACT2802 datasheet(9/21 Pages) ACTIVE-SEMI

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ACT2802

Rev 0, 21-Jan-14

Innovative PowerTM

- 9 -

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Figure 1:

ACT2802 System Operation Flow Chart

FUNCTIONAL DESCRIPTION

Input Current Limit

When the input current reaches the programmed

value, switch Q1 goes into linear mode and output

voltage starts to drop. When output voltage drops to

4.25V, hiccup mode is triggered and switch Q1

turns off and restart in 2 seconds.

Switching Battery Charger

ACT2802 is configured in charge mode (buck

mode) when VIN is valid. In this mode, a battery is

charged with preconditioning, fast charge, top-off

and end of charge (EOC). The typical charge

management is shown in Figure 2 and Figure 3.

CC/CV Regulation Loop

There are CC/CV regulation loops built in ACT2802,

which regulates either current or voltage as

necessary to ensure fast and safe charging of the

battery. In a normal charge cycle, this loop

regulates the current to the value set by the

external resistor at the ICST pin. Charging

continues at this current until the battery cell voltage

reaches the termination voltage. At this point the

CV loop takes over, and charge current is allowed

to decrease as necessary to maintain charging at

the termination voltage.

Precondition Charge

A new charging cycle begins with the precondition

state, and operation continues in this state until VBAT

exceeds the precondition threshold voltage. When

operating in precondition state, the cell is charged

at a reduced current, 10% of the programmed

maximum fast charge constant current. Once VBAT

reaches the precondition threshold voltage the state

machine jumps to the fast charge state.

Fast Charge

battery

voltage

above

preconditioning

threshold, buck converter charges battery with

constant current. In fast charge state, the ACT2802

charges at the current set by the external resistor

connected at the ICST pin. During a normal charge

cycle fast charge continues in CC mode until VBAT

reaches the charge termination voltage, at which

point the ACT2802 charges in top off state.

Top Off

With the battery voltage approaches the EOC

voltage set by the BTV pin. Charge current

decreases as charging continues. In the top off

state, the cell is charged in constant voltage (CV)

mode. During a normal charging cycle charging

proceeds until the charge current decreases below

HZ PIN

VIN Valid

Mode

Boost

Charge

Table 1: Mode Selection

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