ACT81460
Rev 1.0, 18-Dec-2018
problem by providing an additional control loop that pre-
vents VIN from dropping below 4.25V. This function al-
lows the charger to maximize power drawn from the in-
put source without collapsing the input voltage. This
maximizes the power from VIN and minimizes current
from the battery to increase battery life.
and AGND provides temperature information. This in-
formation is used by the charger to comply with the in-
dustry standard JEITA charging guidelines. The NTC
monitoring is designed to work with a typical 10kΩ @
25°C. Figure 4 shows that the NTC pin provides a con-
stant current output that results in a voltage across the
NTC resistor. Internal comparators monitor the NTC
voltage and allow the IC to take the appropriate action
if the measured temperature exceeds the thresholds de-
fined in the JEITA Battery Temperature Control section
of the datasheet. By detecting the pull-down resistor on
the NTC pin, the ACT81460 shall be able to detect pres-
ence of the battery as well as the battery temperature
during charging.
When the system current plus charging current is
greater than the input source’s current capability, the in-
put voltage collapses. When it collapses below the
VDCCC threshold, the charger reduces the charging
current. This prioritizes the system current over the
charging current. If VIN continues to drop, the charger
continues to reduce the charging current in an attempt
to keep VIN regulated to 4.25V or higher. If VIN drops
to 3.8V, the charge current goes to 0A and the charger
goes into supplement mode where it sources current to
VSYS.
The VDCCC threshold is programmable to “Disable”,
4.25V, 4.5V, or 4.75V via I2C register bits VDCCC[1:0].
When set to Disable, the control loop does not limit the
input voltage drop.
NTC
REF_60
REF_50
REF_45
NTC
10K@
25C
In addition to the input voltage regulation, the
ACT81460 can also regulate the total input current. This
allows the user to set the total input current below the
power source’s maximum current rating. This ensures
that the input power source that powers the charger is
not subject to over current and subsequently collapsing
the voltage on the input source. This function in combi-
nation with the input voltage regulation loop allows the
system to maximize the power drawn from the VIN
source for both charging the battery and powering the
system as much as possible to conserve battery power
and extend the battery life of the system.
REF_10
REF_0
Figure 4: NTC Temperature Thresholds
JEITA Battery Temperature Control
To improve the safety of charging Li-ion batteries, the
JEITA guideline was released on April 20, 2007. The
guideline emphasizes the importance of avoiding a high
charge current and high charge voltage at both extreme
low and high temperature ranges. To comply with JEITA
battery charging requirements, and to improve battery
reliability and safety, the ACT81460 reduces the termi-
nation voltage and/or the charging current when the bat-
tery is at temperature extremes. When the battery tem-
perature is outside the normal charging range, the IC
either reduces the safety timer speeds or stops the tim-
ers until the temperature goes back into the normal
charging range. When stopped, the timers are not reset.
They hold their value and resume normal counting when
charging restarts. Refer to the Safety Timer Speed Set-
tings table for specific details.
This maximum input current is programmable to 0.5A,
1A, 1.5A, or 2A via I2C register bits IN_ILIM[1:0]
Die Thermal Regulation
The ACT81460 charger includes a maximum die tem-
perature regulation loop. This feature maximizes charge
current with high ambient thermal conditions. If the
charging conditions increase the die temperature to
115°C, the thermal loop takes over and starts reducing
the charge current. The charge current is linearly re-
duced until the die temperature reaches 150°C. At
150°C, the charging current is 0A. At 155°C the IC re-
ports an interrupt, bit BAT_TEMP_STAT is set to 1, and
Charge Fault is set to 1. Thermal regulation can be dis-
abled by setting I2C bit DIS_THERM_REG to 1.
NTC Battery Temperature Detection
The ACT81460 NTC pin is used to monitor the battery
temperature. An NTC resistor connected between NTC
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