ACT8712QLEHA-T View Datasheet(PDF) - Active-Semi, Inc
Part Name
Description
MFG CO.
ACT8712QLEHA-T
Active-Semi, Inc
'ACT8712QLEHA-T' PDF : 36 Pages View PDF
ACT8712
Rev0, 25-Feb-08
SINGLE-CELL Li+ BATTERY CHARGER (CHGR)
Reverse Leakage Current
The ACT8712 includes internal circuitry that elimi-
nates the need for series blocking diodes, reducing
solution size and cost as well as dropout voltage
relative to conventional battery chargers. When the
input supply is removed, when VVIN goes below its
under-voltage-lockout (UVLO) voltage, or when VVIN
drops below VBAT, the ACT8712 automatically goes
into SUSPEND mode and reconfigures its power
switch to minimize current drain from the battery.
Charger State Machine
PRECONDITION State
A new charging cycle begins in the PRECONDI-
TION state. In this state, the cell is charged at a
reduced current of either 45mA or 10% of the se-
lected maximum fast-charge current, whichever is
greater. During a normal charge cycle, charging
continues at this rate until VBAT reaches the Precon-
dition Threshold Voltage, at which point the state
machine jumps to the FAST-CHARGE state. If VBAT
does not reach the Precondition Threshold Voltage
before the Precondition Charge Timeout period ex-
pires, then a damaged cell is detected and the state
machine jumps to the TIMEOUT-FAULT state.
FAST-CHARGE State
In the FAST-CHARGE state the charger operates in
Constant-Current (CC) mode and charges the cell
at the programmed charge current. During a normal
charge cycle, constant-current charging continues
until VBAT reaches the charge termination voltage, at
which point the state machine jumps to the TOP-
OFF state.
TOP-OFF State
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, decreas-
ing as the cell charges. A normal charging cycle
continues until the charge current decreases to be-
low the End-Of-Charge (EOC) threshold. In order to
improve immunity to conditions that can result in
false-EOC detection, the charging continues until
the EOC condition persists for 4 consecutive min-
utes. Once this condition is met, the charge cycle is
terminated and the state machine jumps to the
SLEEP state.
SLEEP State
In the SLEEP state the ACT8712 presents a high-
impedance to the battery, allowing the cell to “relax”
and minimizing battery leakage current. The
ACT8712 continues to monitor the cell voltage,
however, so that it can reinitiate a charging cycle as
necessary to ensure that the cell remains fully
charged.
Charge Restart
After a charge cycle successfully terminates, the
ACT8712 jumps to its SLEEP state to minimize bat-
tery drain, but continues to actively monitor the cell
voltage. A new charging cycle begins when the cell
voltage has dropped by 200mV (typ), keeping the
cell fully charged. This charge restart process mini-
mizes cycle-life degradation of the cell by allowing it
to “relax” between charges, while ensuring that the
cell remains fully-charged while connected to a
power source.
SUSPEND State
When in the SUSPEND state, the charger is dis-
abled and the charger presents a high-impedance
to the battery, but the charge-control circuitry re-
mains functional. When exiting the SUSPEND
state, the charge timer is reset and the state ma-
chine jumps to the PRECONDITION state.
TIMEOUT-FAULT State
When a TIMEOUT-FAULT occurs, charging is sus-
pended, CHGR/TIMOFLT[ ] is set to [1], and the
charger presents a high-impedance to the battery.
To maximize safety, there is no direct path to re-
sume charging from the TIMEOUT-FAULT state. A
new charging cycle may only be initiated if the state
machine first jumps to the SUSPEND state then
each of the conditions necessary to enter the PRE-
CONDITION state are satisfied.
Innovative Products. Active Solutions.
ActivePMUTM is a trademark of Active-Semi.
I2CTM is a trademark of Philips Electronics.
- 35 -
www.active-semi.com
Copyright © 2008 Active-Semi, Inc.
Share Link: 