ACT8945A
Rev 6, 01-Feb-16
Table 11:
Thermal Regulation
Total Safety Timer Setting
The charger features an internal thermal regulation
loop that monitors die temperature and reduces
charging current as needed to ensure that the die
temperature does not exceed the thermal regulation
threshold of 110°C. This feature protects against
excessive junction temperature and makes the
device more accommodating to aggressive thermal
designs. Note, however, that attention to good
thermal designs is required to achieve the fastest
possible charge time by maximizing charge current.
TOTAL TIME-OUT
PERIOD
TOTTIMO[1] TOTTIMO[0]
0
0
1
1
0
1
0
1
3 hrs
4 hrs
5 hrs
Disabled
Charge Status Indicator
Charge Safety Timers
The charger provides a charge-status indicator
output, nSTAT. nSTAT is an open-drain output
which sinks current when the charger is in an
active-charging state, and is high-Z otherwise.
nSTAT features an internal 8mA current limit, and is
capable of directly driving a LED without the need
of a current-limiting resistor or other external
circuitry. To drive an LED, simply connect the LED
between nSTAT pin and an appropriate supply,
such as VSYS. For a logic-level charge status
indication, simply connect a resistor from nSTAT to
an appropriate voltage supply.
The charger features programmable charge safety
timers which help ensure a safe charge by
detecting potentially damaged cells. These timers
are programmable via the PRETIMO[1:0] and
TOTTIMO[1:0] bits, as shown in Table 10 and Table
11. Note that in order to account for reduced charge
current resulting from DCCC operation in thermal
regulation mode, the charge time-out periods are
extended proportionally to the reduction in charge
current. As a result, the actual safety period may
exceed the nominal timer period.
Charger Timer Interrupts
Table 12:
The charger features the ability to generate
interrupts based upon the status of the charge
Charging Status Indication
STATE
PRECONDITION
FAST-CHARGE
TOP-OFF
nSTAT
Active
Active
Active
High-Z
High-Z
High-Z
High-Z
timers. Set the TIMRPRE[
]
bit to
1
and
TIMRSTAT[ ] bit to 1 to generate an interrupt when
the Precondition Timer expires. Set the TIMRTOT[ ]
bit to 1 and TIMRSTAT[ ] bit to 1 to generate an
interrupt when the Total-Charge Timer expires.
TIMRDAT[ ] indicates the status of the charge
timers. A value of 1 indicates a precondition time-
out or a total charge time-out occurs, a value of 0
indicates other cases.
END-OF-CHARGE
SUSPEND
TEMPERATURE FAULT
TIME-OUT-FAULT
When an interrupt is generated by the charge
timers, reading the TIMRSTAT[ ] returns a value of
1. TIMRSTAT[ ] is automatically cleared to 0 upon
reading. When no interrupt is generated by the
charge timers, reading the TIMRSTAT[ ] returns a
value of 0.
Reverse-Current Protection
The charger includes internal reverse-current
protection circuitry that eliminates the need for
blocking diodes, reducing solution size and cost as
well as dropout voltage relative to conventional
battery chargers. When the voltage at CHGIN falls
below VBAT, the charger automatically reconfigures
its power switch to minimize current drawn from the
battery.
Table 10:
PRECONDITION Safety Timer Setting
PRECONDITION
PRETIMO[1] PRETIMO[0]
TIME-OUT PERIOD
0
0
1
1
0
1
0
1
40 mins
60 mins
80 mins
Disabled
Battery Temperature Monitoring
In a typical application, the TH pin is connected to
the battery pack's thermistor input, as shown in
Figure 7. The charger continuously monitors the
temperature of the battery pack by injecting a
www.active-semi.com
- 40 -
ActivePMUTM and ActivePathTM are trademarks of Active-Semi.
Copyright © 2016 Active-Semi, Inc.
I2CTM is a trademark of NXP.
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