ACT8810
Active- Semi
Rev 4, 01-Oct-09
ActivePathTM CHARGER
FUNCTIONAL DESCRIPTION
System Configuration Optimization
General Description
ActivePath circuitry automatically detects the state
of the input supply, the battery, and the system, and
automatically reconfigures itself to optimize the
power system. If the input supply is present,
ActivePath powers the system in parallel with
charging the battery, so that system power and
charge current can be independently managed to
satisfy all system power requirements. This allows
the battery to charge as quickly as possible, while
ensuring that the total system current does not
exceed the capability of the input supply. If the input
supply is not present, however, then ActivePath
automatically configures the system to draw power
from the battery. Finally, if the input is present and
the system current requirement exceeds the
capability of the input supply, such as under
momentary peak-power consumption conditions,
ActivePath automatically configures itself for
maximum power capability by drawing system
power from both the battery and the input supply.
The ACT8810 incorporates Active-Semi's patent-
pending ActivePath architecture. ActivePath is a
complete battery-charging and system power-
management solution for portable hand-held
equipment. This circuitry performs a variety of
advanced battery-management functions, including
automatic selection of the best available input
supply, current-management to ensure system
power availability, and a complete, high-accuracy
(±0.5%), thermally regulated, full-featured single-
cell linear Li+ charger with an integrated 12V power
MOSFET.
ActivePath Architecture
Active-semi's patent-pending ActivePath
architecture performs three important functions:
1) Input Protection,
2) System Configuration Optimization, and
3) Battery-Management
Battery Management
ActivePath includes a full-featured battery charger
for single-cell Li-based batteries. This charger is a
full-featured, intelligent, linear-mode, single-cell
charger for Lithium-based cells, and was designed
specifically to provide a complete charging solution
with minimum system design effort.
Input Protection
At the input of the ACT8810's ActivePath circuit is
an internal, low-dropout linear regulator (LDO) that
regulates the system voltage (VSYS). This LDO
features a 12V power MOSFET, allowing the
ActivePath system to withstand input voltages of up
to 12V, and additionally includes a variety of other
protection features, including current limit protection
and input over-voltage protection.
The core of the ActivePath's charger is a CC/CV
(Constant-Current/Constant-Voltage), linear-mode
charge controller. This controller incorporates
current and voltage sense circuitry, an internal
80mꢀ power MOSFET, a full-featured state-
machine that implements charge control and safety
features, and circuitry that eliminates the reverse-
blocking diode required by conventional charger
designs.
The ActivePath circuitry provides a very simple
means of implementing a solution that safely
operates within the current-capability limitations of a
USB port while taking advantage of the high output-
current capability of an AC adapter, when available.
ActivePath limits the total current drawn from the
input supply to a value set by the ACIN input; when
ACIN is driven to a logic-low ActivePath operates in
“USB Mode” and limits the current to either 500mA
(when CHGLEV is driven to a logic-high) or to
100mA (when CHGLEV is driven to a logic-low),
and when ACIN is driven to a logic-high ActivePath
operates in “AC-Mode” and limits the input current
to 2A. In either case, ActivePath's DCCC circuitry,
described below, allows the input overload
protection to be adjusted to accommodate a wide
range of input supplies.
This charger also features thermal-regulation
circuitry that protects it against excessive junction
temperature, allowing the fastest possible charging
times, as well as proprietary input protection
circuitry that makes the charger robust against input
voltage transients that can damage other chargers.
The charge termination voltage is highly accurate
(±0.5%), and features a selection of charge safety
timeout periods that protect the system from
operation with damaged cells. Other features
include pin-programmable fast-charge current and
Innovative PowerTM
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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 ]
