ACT8946AQJ203-T
Rev 1.0, 08-Jul-16
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.
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.
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.
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.
Battery Temperature Monitoring
In a typical application, the TH pin is connected to
the battery pack's thermistor input, as shown in
Figure 3. The charger continuously monitors the
temperature of the battery pack by injecting a
102μA (typ) current into the thermistor (via the TH
pin) and sensing the voltage at TH. The voltage at
TH is continuously monitored, and charging is
suspended if the voltage at TH exceeds either of
the internal VTHH and VTHL thresholds of 0.5V and
2.51V, respectively.
Table 8: 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
ACT8946A
102µA
Table 9: Total Safety Timer Setting
TOTAL TIME-OUT
+
VTHH
Li+ Battery
+
TOTTIMO[1] TOTTIMO[0]
Pack
PERIOD
–
TH
0
0
1
1
0
1
0
1
3 hrs
+
NTC
4 hrs
–
VTHL
5 hrs
–
Disabled
Charge Status Indicator
Figure 3: Simple Configuration
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 net resistance (from TH to GA) required to
cross the thresholds are given by:
102μA × RNOM × kHOT = 0.5V → RNOM × kHOT
≈ 5kΩ
102μA × RNOM × kCOLD = 2.51V → RNOM ×
kCOLD ≈ 25kΩ
where RNOM is the nominal thermistor resistance
at room temperature, and kHOT and kCOLD
represent the ratios of the thermistor's resistance at
the desired hot and cold thresholds, respectively, to
the resistance at 25°C.
Table 10: Charging Status Indication
Battery Temperature Interrupts
STATE
PRECONDITION
FAST-CHARGE
TOP-OFF
nSTAT
Active
Active
Active
High-Z
High-Z
High-Z
High-Z
In order to ease detecting the status of the battery
temperature, the charger features the ability to
generate interrupts based upon the status of the
battery temperature. Set the TEMPOUT[ ] bit to 1
and TEMPSTAT[ ] bit to 1 to generate an interrupt
when battery temperature goes out of the valid
temperature range. Set the TEMPIN[ ] bit to 1 and
TEMPSTAT[ ] bit to 1 to generate an interrupt when
battery temperature returns to the valid range.
END-OF-CHARGE
SUSPEND
TEMPERATURE FAULT
TIME-OUT-FAULT
TEMPDAT[ ] indicates the status of the battery
temperature. A value of 1 indicates the battery
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