ACT2813 datasheet(14/23 Pages) ACTIVE-SEMI

14 / 23 page

Rev 2, 19-May-15

Innovative PowerTM

- 14 -

www.active-semi.com

ACT2813/ACT2813C

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.

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

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=5kΩ

60µA×RNOM×kCOLD=1.5V → RNOM×kCOLD= 25kΩ

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.

Figure 14. Input over voltage surge protection circuit

Figure 15.

Battery thermal circuit

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