ACT81460
Rev 1.0, 18-Dec-2018
Voltage
Current
V
TERM
Battery Voltage
Charge Current
ICHG
VPRE
V
TRICKLE
I
PRE
ITERM
ITRICKLE
Trickle
Charge
Pre-
Charge
Fast Charge and Voltage Regulation
Figure 3: APLC Charging Profile
Fast Charge – When the battery voltage is higher than
the precharge voltage, the Fast Charge phase begins.
In this phase, the battery chemistry is ready to accept
the full charging current and the charger applies the full
between 3.9V to 4.52V. The following equation calcu-
lates VTERM.
ꢅꢭꢤꢣꢮ ꢀ 3.9ꢅ ꢥ 20ꢦꢅ ∗ ꢅꢭꢤꢣꢮꢧ4: 0ꢨ
fast charge current, ICHG
.
Where VTERM[4:0] is the decimal equivalent value in
this register. For example, if VTERM[4:0] = 01111 (15
decimal), the termination voltage = 4.2V.
The ACT81460 fast charge current is set by placing a
resistor from the ISET pin to ground. The following
equation calculates the correct RISET resistor value in
ohms
The termination current, ITERM, is set to 5%, 10%, 15%,
or 20% (note that ERD has different values in different
places) of ICHG by I2C register bits ITERM[1:0].
1.2ꢅ
ꢣꢓꢕꢩꢒ
ꢀ
∗ 10,000
End of Charge – When the charge current drops below
ITERM, the charger considers the battery fully charged.
The charge current drops to 0A and the charger contin-
ues to monitor the battery voltage. With no charging cur-
rent, the battery can drop due to self-discharge or due
to being externally loaded. If the battery voltage drops
below the recharge voltage, VRECHG, the charger re-en-
ters the Fast Charge phase. VRECHG is a function of the
ꢁꢪꢫꢬ
Where ICHG is the desired fast charge current in amps.
ISET should stay between 15kΩ and 1.2MΩ to keep the
R
fast charge current between 10mA and 800mA.
During fast charge, the charger regulates a constant
current until the battery voltage reaches the termination
voltage, VTERM. When the battery reaches VTERM,
the charger changes from constant current regulation to
constant voltage regulation. During this time, the
charger keeps the battery at the VTERM voltage and
the charging current starts to drop. When the current
drops below the termination current, ITERM, charging is
terminated and the battery is considered to be at the
end of charge (EOC).
termination
BAT_RECHG_THRESHOLD[1:0].
voltage
and
I2C
register
The
BAT_RECHG_THRESHOLD[1:0] register sets VRECHG
to 80mV, 120mV, 160mV, or 200mV below the termina-
tion voltage.
Input Voltage and Current Control
If the input power source is not capable of supporting
the charging current plus the system current, the VIN
input voltage drops. The ACT81460 eliminates this
The termination voltage threshold, VTERM, is set via
I2C register bits VTERM[4:0]. VTERM is programmable
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