ACT81460
Rev 1.0, 18-Dec-2018
to a maximum of 5.5V by the Smart Switch. The VSYS
output powers the rest of the system and the other con-
verters. The Smart Switch doubles as a linear regulator
to regulate VSYS to voltages lower than VIN.
Charging
Current
VBAT
Current set by
I2C Configurable: 10mA,
25mA
< VTRICKLE
ITRICKLE
I2C Configurable: 5%,
10%, 15%, 20% of ICHG
current
Hardware Configurable:
10mA to 800mA
Softstart
VTRICKLE ~ VPRE
IPRE
The Smart Switch provides softstarting to the VSYS out-
put when input power is applied. This provides a 500µs
controlled ramp time to limit inrush currents.
VPRE ~ VTERM
> VTERM
ICHG
0A
None
Overvoltage Blocking
Table 9: Charging Current Settings
The Smart Switch continuously monitors the VIN volt-
age. If VIN goes above the 5.7V overvoltage threshold,
the switch opens to protect the VSYS bus and all down-
stream loads. It has a 20V blocking capability to handle
extreme overvoltage conditions. When an overvoltage
condition occurs, the ACT81460 opens the Smart
Switch to protect VSYS from the overvoltage condition.
Trickle Charge – When the battery voltage is lower
than the battery short threshold voltage, VBAT_SHORT, the
battery can only accept very low charge currents. The
charger supplies a trickle charge current, ITRICKLE, to
condition the battery and bring a shorted battery pack
“back to life” by allowing the battery protection circuitry
to close its protection FETs. The battery can then be
safely charged to bring the voltage up to a level where
preconditioning can begin.
VSYS Regulator
The Smart Switch regulates VSYS to 4.8V. This pro-
vides a constant VSYS operating voltage, even when
VIN varies. Contact Active Semi if a different VSYS reg-
ulation voltage is required. If VIN is lower than the pro-
grammed regulation voltage, the Smart Switch fully
turns on with a resulting resistance of 200mΩ.
V
TRICKLE is set to 2.0V, 2.2V, 2.4V, or 2.5V via I2C regis-
ter bits V_TRICKLE[1:0].
ITRICKLE is set to 10mA or 25mA via I2C register
I_TRICKLE_SET.
Linear Charger
The ACT81460 autonomously charges a single cell Li-
Ion battery. The IC automatically detects the battery’s
state of charge and starts charging in the proper charge
state. It completes full or partial charging cycles without
host intervention. The charger includes all Li-Ion charg-
ing modes and protection including trickle charging, pre-
charge, fast charge, over and under voltage protection,
JEITA charging profiles, and thermal regulation. It also
includes Active Semi’s ActivePath Architecture.
Precondition Charge - When the battery voltage is
higher than the trickle voltage threshold, the precondi-
tion charge phase begins. In this phase, the IC charges
the battery at a reduced charge current. This safely con-
ditions the battery chemistry to prepare the battery to
accept the full charging current.
The precondition voltage threshold, VPRE, is set via I2C
register bits VPRE[3:0]. The precharge voltage is pro-
grammable between 2.7V to 3.4V. The following equa-
tion calculates the precharge voltage.
Charger Enable
The charger is automatically enabled when the VSYS
voltage is greater than the battery voltage by > 100mV.
The charger can be enabled and disabled by I2C bit
CHG_EN.
ꢅꢢꢣꢤ ꢀ 2.7ꢅ ꢥ 50ꢦꢅ ∗ ꢅꢢꢣꢤꢧ3: 0ꢨ
Where VPRE[3:0] is the decimal equivalent value in this
register. For example, if VPRE[3:0] = 0110 (6 decimal),
the precharge voltage = 3.0V.
Battery Charging Profile
The precharge current, IPRE, is set by I2C register bits
IPRE[1:0]. The constant current is set to 5%, 10%, 15%
or 20% of the fast charge current setting.
The IC follows the standard Li-Ion battery charge profile
with four charging phases: trickle charge, precondition-
ing, constant current, and constant voltage. The battery
charge current is a function the battery voltage and the
IC’s hardware and register settings. Figure 2 shows the
charge profile and Table 9 shows these available set-
tings.
The constant current, precondition phase continues un-
til the battery voltage increases to the precondition volt-
age threshold.
Innovative PowerTM
ActiveSwitcherTM is a trademark of Active-Semi
www.active-semi.com
Copyright © 2018 Active-Semi, Inc.
49
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
