ACT8933
Rev 3, 15-Nov-12
minimizing battery current drain and allowing the
cell to “relax”. The charger continues to monitor the
cell voltage, and re-initiates a charging sequence if
the cell voltage drops to 205mV (typ) below the
charge termination voltage.
Charge-Control State Machine
PRECONDITION State
new charging cycle begins with the
A
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 10%
of the programmed maximum fast-charge constant
SUSPEND State
The state-machine jumps to the SUSPEND state
any time the battery is removed, and any time the
input voltage either falls below the CHGIN UVLO
threshold or exceeds the OVP threshold. Once
none of these conditions are present, a new charge
cycle initiates.
current, ICHG
.
Once VBAT reaches the Precondition Threshold
Voltage, the state machine jumps to the FAST-
CHARGE state. If VBAT does not reach the
Precondition Threshold Voltage before the
Precondition Time-out period expires, then the state
machine jumps to the TIME-OUT-FAULT state in
order to prevent charging a damaged cell. See the
Charge Safety Timers section for more information.
A charging cycle may also be suspended manually
by setting the SUSPEND[ ] bit. In this case, initiate
a new charging sequence by clearing SUSPEND[ ]
to 0.
State Machine Interrupts
FAST-CHARGE State
The charger features the ability to generate
interrupts when the charger state machine
transitions, based upon the status of the CHG_ bits.
Set CHGEOCIN[ ] bit to 1 and CHGSTAT[ ] bit to 1
to generate an interrupt when the charger state
machine goes into the END-OF-CHARGE (EOC)
state. Set CHGEOCOUT[ ] bit to 1 and CHGSTAT[ ]
bit to 1 to generate an interrupt when the charger
state machine exits the EOC state.
In the FAST-CHARGE state, the charger operates
in constant-current (CC) mode and regulates the
charge current to the current set by RISET . Charging
continues in CC mode until VBAT reaches the charge
termination voltage (VTERM), at which point the state-
machine jumps to the TOP-OFF state. If VBAT does
not reach VTERM before the total time out period
expires then the state-machine will jump to the
“EOC” state and will re-initiate a new charge cycle
after 32ms “relax”. See the Current Limits and
Charge Current Programming sections for more
information about setting the maximum charge
current.
CHGDAT[ ] indicates the status of the charger state
machine. A value of 1 indicates that the charger
state machine is in END-OF-CHARGE state, a
value of 0 indicates the charger state machine is in
other states.
When an interrupt is generated by the charger state
machine, reading the CHGSTAT[ ] returns a value
of 1. CHGSTAT[ ] is automatically cleared to 0 upon
reading. When no interrupt is generated by the
charger state machine, reading the CHGSTAT[ ]
returns a value of 0.
TOP-OFF State
In the TOP-OFF state, the cell charges in constant-
voltage (CV) mode. In CV mode operation, the
charger regulates its output voltage to the 4.20V
charge termination voltage, and the charge current
is naturally reduced as the cell approaches full
charge. Charging continues until the charge current
drops to END-OF-CHARGE current threshold, at
which point the state machine jumps to the END-
OF-CHARGE (EOC) state.
For additional information about the charge cycle,
CSTATE[0:1] may be read at any time via I2C to
determine the current charging state.
Table 11:
If the state-machine does not jump out of the TOP-
OFF state before the Total-Charge Time-out period
expires, the state machine jumps to the EOC state
and will re-initiate a new charge cycle if VBAT falls
below termination voltage 205mV (typ). For more
information about the charge safety timers, see the
Charging Safety Times section.
Charging Status Indication
CSTATE[0] CSTATE[1] STATE MACHINE STATUS
1
1
1
0
PRECONDITION State
FAST-CHARGE/
TOP-OFF State
0
0
1
0
END-OF-CHARGE State
END-OF-CHARGE (EOC) State
SUSPEND/DISABLED/
FAULT State
In the END-OF-CHARGE (EOC) state, the charger
presents
a
high-impedance to the battery,
Innovative PowerTM
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