ACT5830
Rev PrB, 05-Mar-08
SINGLE-CELL Li+ BATTERY CHARGER (CHGR)
FUNCTIONAL DESCRIPTIONS CONT’D
TOP-OFF State
Charge Safety Timer
In the TOP-OFF state, the cell is charged in con-
stant-voltage (CV) mode. With the charge current
limited by the internal chemistry of the cell, de-
creases as charging continues. During a normal
charging cycle charging proceeds until the charge
current decreases beyond the End-Of-Charge
(EOC) threshold, defined as 10% of ISET. When
this happens, the state machine terminates the
charge cycle and jumps to the SLEEP state.
While monitoring the charge cycle, the ACT5830
utilizes a charge safety timer to help identify dam-
aged cells and to ensure that the cell is charged
safely. Three timeout options of 60 minutes, 30 min-
utes, and 45minutes are available, as programmed
by the CHGR/TIMOSET register, and a timer-
disable option is also available for systems that do
not require the ACT5830 to control charge timeouts.
The bit assignments for each timeout period are set
as follows:
SLEEP State
In SLEEP mode the ACT5830 presents a high-
impedance to the battery, allowing the cell to “relax”
and minimizing battery leakage current. The
ACT5830 continues to monitor the cell voltage,
however, so that it can re-initiate charging cycles as
necessary to ensure that the cell remains fully
charged. Under normal operation, the state ma-
chine initiates a new charging cycle by jumping to
the FAST-CHARGE state when VBAT drops below
the Charge Termination Threshold (programmed by
VSET) by more than the Charge Restart Threshold
of 200mV (typ).
Table 12:
TIMOSET[ ] Timeout Period Options
TIMOSET PRECONDITION TOTAL CHARGING
[1:0 ]
TIMEOUT
TIMEOUT
0
0
1
0
1
60 mins (default)
3.0 hours (default)
0
1
1
TIMER DISABLED TIMER DISABLED
30 mins
45 mins
1.5 hours
2.2 hours
SUSPEND State
CHGR State-Machine
The ACT5830 features a user-selectable suspend-
charge mode (SUSCHG), which disables the
charger but keeps other circuitry functional. Charg-
ing continues in the SUSPEND state until
CHGR/SUSPEND is cleared, at which point the
charge timer is reset and the state machine jumps
to the PRECHARGE state.
PRECONDITION State
A new charging cycle begins with the PRECONDI-
TION state. In this state, the cell is charged at a
reduced current of 10% of ISET, the programmed
fast charge current. During a normal charge cycle,
charging continues at this rate until VBAT reaches
the Precondition Threshold Voltage of 2.9V (typ), at
which point the charging state machine jumps to its
FAST-CHARGE state. If VBAT does not reach the
Precondition Threshold Voltage before the charge
timeout period expires, then a damaged cell is de-
tected and the state machine jumps to the TIME-
OUT-FAULT State.
Suspend charge by setting CHGR/SUSCHG = [1].
Permit charging by clearing CHGR/SUSCHG to [0].
TIMEOUT-FAULT State
In order to prevent continued operation with a dam-
aged ce ll, there is no direct path to resume charg-
ing once a Timeout Fault occurs. In order to resume
charging, the state machine must jump to the SUS-
PEND state as a result of any of the following
events:
FAST-CHARGE State
In FAST-CHARGE mode, the charger operates in
constant-current (CC) mode and charges the cell at
the current programmed by CHGR/ISET. During a
normal charge cycle fast-charge continues until
VBAT reaches the termination voltage programmed
by VSET, at which point the state machine jumps to
the TOPOFF state.
microprocessor sets CHGR/SUSCHG to [1],
microprocessor pulls nENCHG high,
the input supply is removed or the input suppl volt-
age drops below the UVLO threshold (4V), or
the battery is removed. Once any of these events
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