ACT2813/ACT2813C
Rev 2, 19-May-15
Input Over Voltage Surge
In the case of pure ceramic input capacitor is
chosen, if the input cable is long, stray inductance
may cause over voltage spikes as twice as the
steady-state voltage when input source is plugged
in. Below input circuit is recommended to avoid
input voltage surge. R1 resistor is added in series
with capacitor C1 to damp the potential LC
resonance as shown in Figure 14.
Figure 15. Battery thermal circuit
Figure 14. Input over voltage surge protection circuit
Inductor and Capacitor Selection
ACT2813/ACT2813C supports SMD components.
2.2uH inductor is recommended. Input side, 4.7uF
ceramic capacitor in series with 2.7Ω resistor are
recommended, on battery side, 22uF ceramic
capacitors is recommended while on output side,
22uFx3 ceramic capacitors are recommended.
Battery Temperature Monitoring
ACT2813 continuously monitors the temperature of
the battery pack by sensing the resistance of its
thermistor, and suspends charging if the
temperature of the battery pack exceeds the safety
limits.
In a typical application, the TH pin is connected to
the battery pack's thermistor input as shown in
Figure 15. The ACT2813 injects a 60µA current out of
the TH pin into the thermistor, so that the thermistor
resistance is monitored by comparing the voltage at
TH to the internal VTHL and VTHH thresholds of 0.3V
and 1.5V, respectively. When VTH > VTHH or VTH < VTHL
charging and the charge timers are suspended. When
VTH returns to the normal range, charging and the
charge timers resume.
The threshold is given by:
60µA×RNOM×kHOT=0.3V→ RNOM×kHOT=5kꢀ
60µA×RNOM×kCOLD=1.5V → RNOM×kCOLD= 25kꢀ
where RNOM is the nominal thermistor resistance at
room temperature, and kHOT and kCOLD are the ratios of
the thermistor's resistance at the desired hot and cold
thresholds, respectively.
Innovative PowerTM
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