ACT8810
Active- Semi
Rev 4, 01-Oct-09
ActivePathTM CHARGER
FUNCTIONAL DESCRIPTION CONT’D
End of Charge State
Charger State-Machine
In the End-of-Charge (EOC) state, the ACT8810
presents a high-impedance to the battery, allowing
the cell to “relax” and minimizes battery leakage
current. The ACT8810 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.
PRECONDITION State
A
new charging cycle begins with the
PRECONDITION state, and operation continues in
this state until VBAT exceeds the Precondition
Threshold Voltage of 2.85V (typ). When operating
in PRECONDITION state, the cell is charged at a
reduced current, 12% of the programmed maximum
fast-charge constant current, ISET. Once VBAT
reaches the Precondition Threshold Voltage the
state machine jumps to the NORMAL state. If VBAT
does not reach the Precondition Threshold Voltage
before the Precondition Timeout period tPRECONDITION
expires, then a damaged cell is detected and the
state machine jumps to the TIMEOUT-FAULT State.
For the Precondition Timeout period, see the
Charging Safety Timers section for more information.
SUSPEND State
The ACT8810 features an user-selectable suspend-
charge mode, which disables the charger but keeps
other circuiting functional. The charger can be put
into suspend mode by driving EN to logic low. Upon
exiting the SUSPEND State, the charge timer is
reset and the state machine jumps to
PRECONDITION state.
SLEEP State
FAST CHARGE State
In SLEEP mode the ACT8810 presents a high-
impedance to the battery, allowing the cell to “relax”
and minimizes battery leakage current. The
ACT8810 continues to monitor the cell voltage,
however, so that it can re-initiate charging as
necessary to ensure that the cell remains fully
charged. Under normal operation, the state
machine initiates a new charging cycle by jumping
to the FAST-CHARGE state when VBAT drops below
the Charge Termination Threshold.
Normal state is made up of two operating modes,
fast charge Constant-Current (CC) and Constant-
Voltage (CV). In CC mode, the ACT8810 charges at
the current programmed by RISET (see the Current
Limits and Charge Current Programming section for
more information). During a normal charge cycle
fast-charge continues in CC mode until VBAT
reaches the charge termination voltage (VTERM), at
which point the ACT8810 charges in CV mode.
Charging continues in CV mode until the charge
current drops to 10% (ACIN = 1) or 5% (ACIN = 0)
of the programmed maximum charge current, at
which point the state machine jumps to the TOP-
OFF state. If VBAT does not proceed out of the
NORMAL state before the Normal Timeout period
(TNORMAL) expires, then a damaged cell is detected
and the state machine jumps to the TIMEOUT-
FAULT State. See the Charging Safety Times
section for more information.
CHG_IN Bypass Capacitor Selection
CHG_IN is the power input for the ACT8810 battery
charger. The battery charger is automatically
enabled whenever a valid voltage is present on
CHG_IN. In most applications, CHG_IN is
connected to either a wall adapter or USB port.
Under normal operation, the input of the charger will
often be “hot-plugged” directly to a powered USB or
wall adapter cable, and supply voltage ringing and
overshoot may appear at the CHG_IN pin.
TOP-OFF State
In most applications a high quality capacitor
connected from CHG_IN to GA, placed as close as
possible to the IC, is sufficient to absorb the energy.
Wall-adapter powered applications provide flexibility
in input capacitor selection, but the USB
specification presents limitations to input
capacitance selection. In order to meet both the
USB 2.0 and USB OTG (On The Go) specifications
while avoiding USB supply under-voltage conditions
In the TOP-OFF state, the cell is charged in
constant-voltage (CV) mode. Charge current
decreases as charging continues. During a normal
charging cycle charging proceeds until the charge
current decreases below the End-Of-Charge (EOC)
threshold, defined as 10% of ISET (ACIN = 1) or
5% of ISET (ACIN = 0) . When this happens, the
state machine terminates the charge cycle and
jumps to the SLEEP state.
Innovative PowerTM
- 50 -
www.active-semi.com
ActivePMUTM and ActivePathTM are trademarks of Active-Semi.
I2CTM is a trademark of Philips Electronics.
Copyright © 2009 Active-Semi, Inc.
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
