BQ24740_07 Datasheet, PDF (23/32 Pages) Texas Instruments – Host-controlled Multi-chemistry Battery Charger with Low Input Power Detect

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APPLICATION INFORMATION
bq24740
SLUS736 – DECEMBER 2006
Input Capacitance Calculation
During the adapter hot plug-in, the ACDRV has not been enabled. The AC switch is off and the simplified
equivalent circuit of the input is shown in Figure 29.
Ii
Ri Li
Vi
C1
C8 Ci _Vc
A. Ri and Li are the equivalent input inductance and resistance. C1 and C8 are the input capacitance.
Figure 29. Simplified Equivalent Circuit During Adapter Insertion
The voltage on the input capacitor(s) is given by:
V_C (t) =
V_C (0) +
V_i × w
Z₀ × C_i × w²⁰
+
Z₀
V_i
× C_i
× w₀₂
e
-
R_i
2L_i
t
ççèæ
-
R_i
2L _i
sin wt - w × cos wt _{÷÷øö}
(5)
Z₀ =
where
L_{i w =}
C_{i ,}
1
L_iC_i
-
ççèæ
R_i
2L _i
÷÷øö ²
,
and
w₀
=
1
L_iC_i
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