ACT2803
Rev 1, May-12-2016
FUNCTIONAL DESCRIPTION
ACT2803 is a complete battery charging and
discharging power management solution for
applications of dull-cell lithium-based backup
battery pack or power bank.
threshold, boost converter charges battery with
constant current. In fast charge state, the ACT2803
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 ACT2803 charges in top off state.
With the advanced bidirectional architecture, a
synchronous boost/buck converter is connected
from VOUT to switching node (SW). The converter
could be configured as either boost to charge
battery or buck to discharge battery.
Top Off
Device transitions from Fast Charge (CC) to Top
Off (CV), and moves to EOC (End of Charge) state
Modes of Operation
when charging current is less than IEOC
.
ACT2803 has 3 operation modes: charge mode,
discharge mode, and high-impedance (HZ) mode.
End of Charge
In Top Off mode, when charges current decreases
to 10% of set fast charge current, the boost
converter goes into end of charge mode and keep
monitoring the battery voltage.
High Impedance (HZ) Mode
HZ mode is the default mode. In HZ mode, all the
switches are turned off , only PB circuit alive and
the IC draws less than 10uA current from VBAT.
Recharge
Discharge Mode
In EOC, device would re-charge batteries when
In discharge mode, Buck converter operates in CV/
CC regulation. VOUT current limit is set at 2.65A.
both battery voltage levels drops 5% below VEOC
.
Battery Removal
Charge Mode
If the battery is removed, boost converter regulates
at the programmed regulation voltage.
ACT2803 is configured in charge mode (boost
mode) when VIN is valid. In this mode, a battery is
charged with trickle, preconditioning, fast charge,
top-off and end of charge (EOC). The typical
charge management is shown in Figure 1.
Cell Balance
Cell Balance is activated in both Fast Charge and
Top Off modes. Each battery is connected with a
parallel bleeding switch.
Precondition Charge
When operating in precondition state, the cell is
charged at a reduced current at 15% of the
programmed maximum fast charge constant
current. Once VBAT reaches the precondition
threshold voltage the state machine jumps to the
fast charge state.
Push Button
PB is always watched in HZ mode and discharge
mode. If the push but on PB is pressed for >40mS
in HZ mode, the LED (s) will turn on for 5 seconds.
In the mean time, discharge mode is enabled.
Fast Charge
If battery voltage is above preconditioning
A: PRECONDITION STATE
B: FAST-CHARGE STATE
C: TOP-OFF STATE
D: END-OF-CHARGE STATE
Figure 1. Typical Li+ Charge Profile and ACT2803 Charge States
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