ACT8933
Rev 3, 15-Nov-12
ActivePathTM CHARGER
General Description
In an input over-voltage condition this circuit limits
VVSYS to 4.6V, protecting any circuitry connected to
VSYS from the over-voltage condition, which may
exceed this circuitry's voltage capability. This circuit
is capable of withstanding input voltages of up to
12V.
The ACT8933 features an advanced battery
charger that incorporates the patent-pending
ActivePath architecture for system power selection.
This combination of circuits provides a complete,
advanced battery-management system that
automatically selects the best available input
supply, manages charge current to ensure system
power availability, and provides a complete, high-
accuracy (±0.5%), thermally regulated, full-featured
single-cell linear Li+ charger that can withstand
input voltages of up to 12V.
Table 9:
Input Over-Voltage Protection Setting
OVPSET[1]
OVPSET[0]
OVP THRESHOLD
0
0
1
1
0
1
0
1
6.6V
7.0V
7.5V
8.0V
ActivePath Architecture
The ActivePath architecture performs three
important functions:
Input Supply Overload Protection
1) System Configuration Optimization
2) Input Protection
The ActivePath circuitry monitors and limits the total
current drawn from the input supply to a value set
by the ACIN and CHGLEV inputs, as well as the
resistor connected to ISET. Drive ACIN to a logic-
low for “USB Mode”, which limits the input current to
either 100mA, when CHGLEV is driven to a logic-
low, or 450mA, when CHGLEV is driven to a logic-
high. Drive ACIN to a logic-high for “AC-Mode”,
which limits the input current to 2A, typically.
3) Battery-Management
System Configuration Optimization
The ActivePath circuitry monitors the state of the
input supply, the battery, and the system, and
automatically reconfigures itself to optimize the
power system. If a valid input supply is present,
ActivePath powers the system from the input while
charging the battery in parallel. This allows the
battery to charge as quickly as possible, while
supplying the system. If a valid input supply is not
present, ActivePath powers the system from the
battery. Finally, if the input is present and the
system current requirement exceeds the capability
of the input supply, ActivePath allows system power
to be drawn from both the battery and the input
supply.
Input Under Voltage Lockout
If the input voltage applied to CHGIN falls below
3.5V (typ), an input under-voltage condition is
detected and the charger is disabled. Once an input
under-voltage condition is detected, a new charge
cycle will initiate when the input exceeds the under-
voltage threshold by at least 500mV.
Battery Management
The ACT8933 features a full-featured, intelligent
charger for Lithium-based cells, and was designed
specifically to provide a complete charging solution
with minimum system design effort.
Input Protection
Input Over-Voltage Protection
The core of the charger is a CC/CV (Constant-
Current/Constant-Voltage), linear-mode charge
controller. This controller incorporates current and
voltage sense circuitry, an internal 70mꢀ power
The ActivePath circuitry features input over-voltage
protection circuitry. This circuitry disables charging
when the input voltage exceeds the voltage set by
OVPSET[-] as shown in Table 9, but stands off the
input voltage in order to protect the system. Note
that the adjustable OVP threshold is intended to
provide the charge cycle with adjustable immunity
against upward voltage transients on the input, and
is not intended to allow continuous charging with
input voltages above the charger's normal operating
voltage range. Independent of the OVPSET[-]
setting, the charge cycle is not allowed to resume
until the input voltage falls back into the charger's
normal operating voltage range (i.e. below 6.0V).
MOSFET, thermal-regulation circuitry,
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 charge termination voltage is highly accurate
(±0.5%), and features a selection of charge safety
time-out periods that protect the system from
operation with damaged cells. Other features
Innovative PowerTM
www.active-semi.com
- 37 -
Active-Semi Proprietary―For Authorized Recipients and Customers
ActivePMUTM and ActivePathTM are trademarks of Active-Semi.
I2CTM is a trademark of NXP.
Copyright © 2012 Active-Semi, Inc.
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
