BQ24751RHDRG4 Datasheet, PDF (29/38 Pages) Texas Instruments – Host-controlled Multi-chemistry Battery Charger

bq24751
www.ti.com............................................................................................................................................... SLUS734D – DECEMBER 2006 – REVISED MARCH 2009
APPLICATION INFORMATION
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 37.
IIN
VIN
Ri Li
Rc
Vi
Ci _Vc
Figure 37. Simplified Equivalent Circuit During Adapter Insertion
The voltage on the input capacitor(s) is given by:
V_IN
(t) =
I_IN
(t)´ R_C
+
V_{Ci(t )}
=
R_i
V_ie ^2Li
t
é
ê
ë
R_i -R_C
wL_i
sin wt
+
cos
w
t
ù
ú
û
(6)
in which,
Rt = Ri + RC w =
1
LiCi
-
æ
ç
Rt
ö²
÷
è ^2Li ø
IIN (t) =
Vi
Ri _t
e ^2Li sin wt
wLi
(7)
Rt _t
VCi (t) = Vi - Vie ^2Li
æ
ç
Rt
ö
sin wt + coswt _÷
è ^2wLi
ø
(8)
The damping conditions is:
L
R
i
=
R
C
>
2
C
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