ACT2802
Rev 0, 21-Jan-14
Table 4: Battery Impedance
Flashlight Circuit
RIMC(KΩ)
50
50
100
100
200
200
200
400
Figure 16 shows a circuit with flashlight driver and
control.
Battery
Impedance
R(mΩ)
Rcs=25mΩ
Rcs=50mΩ
100
Boost Output Plug-in Auto Detection
Figure 13 provides a solution for auto plug-in
detection.
Figure 16. Flashlight circuit
LEDs on in Boost Mode
LEDs can be always on during boost mode, the
schematic is shown in Figure17.
Figure 13. Boost output auto detection circuit
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 17. LEDs on in boost mode circuit
Inductor and Capacitor Selection
ACT2802 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,
22uFx2 ceramic capacitors are recommended.
Battery Temperature Monitoring
Figure 14. Input over voltage surge protection circuit
The ACT2802 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.
External Input Over Voltage Protection
Considering the maximum voltage rating at VIN pin,
the external OVP circuit as shown in Figure 15 is
recommended if input voltage may go higher than
7V. With the enhanced OVP circuit, input voltage
can be up to 18V.
In a typical application, the TH pin is connected to
the battery pack's thermistor input as shown in
Figure 18. The ACT2802 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 net resistance from TH to GND required to cross
Figure 15. Input over voltage protection
Innovative PowerTM
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