ACT2823
REV 1, 01-DEC-2016
The following table provides the recommended RICST
values based on RCS=25mΩ and 50mΩ.
110°C. If the die temperature increases above 110°C,
the IC reduces charging current at a rate of -10%/°C.
This ensures that the output voltage on VOUT has
priority over charging the battery. In discharge mode,
the IC delivers full current at rated voltage when the
temperature is below 130°C. If the die temperature
increases above 130°C, the IC decreases the output
voltage by -115mV/°C.
RICST
IC (A)
Units
RCS=25mΩ RCS=50mΩ
0.8
0.9
1
10
5
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
8.89
8
4.44
4
End-of-Charge Timer
1.1
1.2
1.3
1.4
1.5
7.27
6.67
6.15
5.71
5.33
3.64
3.33
3.08
2.86
2.67
When the charger enter the End-of-Charge mode, it
either immediately stops charging or continues to
charge for 45 minutes. If register 0x04h, bit 7 = 0, the
charger immediately turns off. If this bit = 1, the charger
continues to charge in constant voltage mode for 45
minutes.
Power Path Priority
Top Off
The ACT2823 always gives priority to the system
voltage on VOUT. If the input voltage source is current
limited and cannot simultaneously provide the full
charge current plus the full system current (current out
of VOUT), the input voltage would drop and cause a
brownout situation on VOUT. The ACT2823 avoids the
brownout condition by reducing the charging current if
the input voltage drops. If the IC detects that a USB
cable is connected, the Charge Current Foldback
Threshold voltage starts at 4.92V. If no USB cable is
detected, the starting voltage is 4.7V. The charger
linearly reduces charge current from full charge current
to 0A as the voltage on VIN drops from 4.7V to 4.6V or
from 4.92V to 4.82V, depending on whether or not a
USB cable is detected.
When the battery voltage reaches the End-of-Charge
Voltage, the ACT2823 transitions to Top Off mode. Top
Off mode charges the battery with a constant voltage.
In Top Off mode, the charging current slowly decreases
as the actual battery voltage increases and the voltage
across the battery’s ESR decreases. The charger stays
in Top Off mode until the charging current drops below
the EOC (End-of-Charge) current which is 10% of the
programmed fast charge current. At this point the
battery is considered fully charged and the charger
transitions into the End of Charge mode.
End-of-Charge
When the charging current drops to 10% of the fast
charge current, the charger enters End-of-Charge mode.
If register 0x04h, bit 7 = 0, the charger immediately turns
off. If this bit = 1, the charger continues to charge in
constant voltage mode for 45 minutes. In this case, the
charge current continues to drop while the battery
voltage is held at the End-of-Charge voltage. If the
battery voltage drops below 95% of the End-of-Charge
voltage, the charger transitions back into Top Off mode.
The charger automatically transitions between these
four charging modes as the battery voltage increases
and decreases during charging and discharging cycles.
The charger also reduces the charging current if the
total input current (charging current plus system current)
exceeds 80% of the programmed input current limit
(ILIM) threshold of 3.8A. Charging current is linearly
reduced from full charge current to 0A as the input
current increases from 80% of ILIM to 100% of ILIM.
Operating Modes
The ACT2823 automatically switches between several
different operating modes, depending on circuit
conditions.
If a battery is not present during charging mode, the
charger regulates its output to the End-of-Charge
voltage. If a battery is then connected, the charger
automatically transitions to the proper operating mode
that is appropriate for the battery’s voltage. If the battery
disconnected from the charger, it regulates its output to
the End-of-Charge voltage
Charge Mode
When input power is applied and there are no faults, the
IC operates in Charge Mode. Charge Mode turns on Q1
to power VOUT with the input voltage. Note that Q1
stays off and VOUT is not present in Trickle Charge
mode. Charge mode configures the switches Q2 and
Q3 as a boost converter to charge the battery. The IC
automatically enters Charge Mode when input power is
applied. There is a 2s delay when transitioning from
Discharge Mode to charge mode. During this time, the
IC goes into HZ mode
Thermal Regulation
The charger contains a thermal regulation feature that
prevents the IC from reaching thermal shutdown in high
temperature environments. It works in both charge and
discharge modes. The charger operates at full charging
current when the ACT2823 die temperature is below
Innovative PowerTM
ActiveSwitcherTM is a trademark of Active-Semi.
13
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
