ACT2802B datasheet(11/25 Pages) ACTIVE-SEMI

11 / 25 page

Rev 7, 15-Jul-16

Innovative PowerTM

- 11 -

www.active-semi.com

ACT2802/ACT2802B/ACT2802C

Figure 2:

ACT2802B/ACT2802C System Operation Flow Chart

FUNCTIONAL DESCRIPTION

Latch-Off

ACT2802/ACT2802B/ACT2802C

has

latch

off

function. If discharging stops due to battery cut-off,

and latch off will be triggered, it would prevent

battery from discharging again, latch-off is released

when input power is recycled.

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/ACT2802B/ACT2802C 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 3

and Figure 4.

CC/CV Regulation Loop

There are CC/CV regulation loops built in ACT2802/

ACT2802B/ACT2802C,

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/

ACT2802B/ACT2802C 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/

ACT2802B/ACT2802C 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

the end of charge (EOC) threshold, defined as 15%

of fast charge current. When this happens, the state

machine terminates the charge cycle and jumps to

the EOC state.

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