ACT2801_14 datasheet(10/23 Pages) ACTIVE-SEMI

10 / 23 page

Rev 2, 15-Apr-14

Innovative PowerTM

- 10 -

www.active-semi.com

ACT2801/ACT2801C

Figure 2:

ACT2801C 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

ACT2801/ACT2801C 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 ACT2801/

ACT2801C, 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 ACT2801/

ACT2801C 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 ACT2801/ACT2801C

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 13%

of fast charge current. When this happens, the state

machine terminates the charge cycle and jumps to

the EOC state.

End of Charge

When charges current decreases to 13% of set fast

charge current, the buck converter goes into end of

charge mode and keep monitoring the battery

voltage.

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