ACT2801/ACT2801B/ACT2801C
Rev 9, 14-Mar-17
The IOST pin voltage is proportional to output
current until output current is limited, as shown in
Figure 15.
Input
VIN
Rcs
50mΩ
L 2.2uH
R1 2.7Ω
SW
900
C1 4.7uF
VBAT = 3.7V
RIOST=97.6kΩ
750
BAT
Battery
600
450
300
150
0
Figure 17. Input over voltage surge protection circuit
Boost Output Plug-in Auto Detection
Figure 18 provides a solution for auto plug-in
0
0.2
0.4
0.6
0.8
1.0
1.2
detection.
Output current(A)
Figure 15. VIOST VS. output current
VBAT
Battery
Impedance Compensation
715K
PB
Rcs
50mΩ
L 2.2uH
PB
SW
An external resistor is used to set the impedance
from 40mΩ to 500mΩ as shown in Figure 16. RIMC
is corresponding to battery impedance. Higher RIMC
gives higher compensation voltage which is
positively proportional to battery charge/discharge
current.
200K
2.2uF
715K
2.2uF
BAT
Battery
HZ
VOUT
+
D-
COUT
D+
-
USB Shielding Ground
Select RIMC based on battery impedance:
Figure 18. Boost output auto detection circuit
25 R (m )
(6)
R
IMC(k )
Rcs (m )
VBAT (V ) BAT(V ) IBAT (A) R(m )10-3
External Input Over Voltage Protection
(7)
Considering the maximum voltage rating at VIN pin,
the external OVP circuit as shown in Figure 19 is
recommended if input voltage may go higher than
7V. With the enhanced OVP circuit, the design can
pass UN38.3.
Input
Output
VOUT
VIN
Cout
L
Rcs
R:
SW
Battery Impedance
RIMC
Si2365EDS
Input
IBAT
RIMC
R
VIN
Battery
package
BAT
10k
Q2
3906
2.7Ω
Q1
Figure 16. Battery impedance compensation setting circuit
4.7k
4.7uF
D1
5.6V
The battery impedance as shown in the table 4
according to the RIMC and Rcs:
10k
Table 4: Battery Impedance
Figure 19. Input over voltage protection
RIMC(KΩ)
50
50
100
100
200
200
200
400
Inductor and Capacitor Selection
Rcs=25mΩ
Rcs=50mΩ
Battery
Impedance
ACT2801/ACT2801B/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 side,
22uF ceramic capacitors is recommended while on
output side, 2*22uF ceramic capacitors are
recommended.
R(mΩ)
100
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 17.
Battery Temperature Monitoring
ACT2801 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
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