ACT2801CQL-T datasheet(14/23 Pages) ACTIVE-SEMI

14 / 23 page

Rev 2, 15-Apr-14

Innovative PowerTM

- 14 -

www.active-semi.com

ACT2801/ACT2801C

Table 4: Battery Impedance

Boost Output Plug-in Auto Detection

Figure 14 provides a solution for auto plug-in

detection.

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 15.

External Input Over Voltage Protection

Considering the maximum voltage rating at VIN pin,

the external OVP circuit as shown in Figure 16 is

recommended if input voltage may go higher than

7V. With the enhanced OVP circuit, input voltage

can be up to 18V.

LEDs on in Boost Mode

LEDs can be always on during boost mode, the

schematic is shown in Figure17.

Inductor and Capacitor Selection

ACT2801/ACT2801C supports SMD components.

2.2uH inductor is recommended. Input side, 4.7uF

ceramic capacitor in series with 2.7Ω resistor are

recommended, on battery and output sides, 22uF

ceramic capacitors are recommended.

Battery Temperature Monitoring

ACT2801 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 18. The ACT2801 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.

RIMC(KΩ)

100

200

Battery

Impedance

R(mΩ)

Rcs=25mΩ

100

200

Rcs=50mΩ

100

200

400

Figure 14.

Boost output auto detection circuit

Figure 15. Input over voltage surge protection circuit

Figure 16.

Input over voltage protection

Figure 17. LEDs on in boost mode circuit

Figure 18.

Battery thermal circuit

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