ACT2802/ACT2802B/ACT2802C
Rev 7, 15-Jul-16
FUNCTIONAL DESCRIPTION
Figure 2:
ACT2802B/ACT2802C System Operation Flow Chart
charging at the termination voltage.
Latch-Off
Precondition Charge
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.
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.
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.
Fast Charge
If battery voltage is 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.
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.
Top Off
CC/CV Regulation Loop
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.
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
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2016 Active-Semi, Inc.
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
