Datasheet


SLVS612 − APRIL 2006
10
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APPLICATION INFORMATION
Stepping the load from a heavy load to a light load results in an output overshoot. Excess energy stored in the
inductor must be absorbed by the output capacitance. The energy stored in the inductor is described in
equation (5).
E
L
+
1
2
L I
2
(Joules)
where:
I
2
+
ƪ
ǒ
I
OH
Ǔ
2
*
ǒ
I
OL
Ǔ
2
ƫ
ǒ
(
Amperes
)
2
Ǔ
where:
D I
OH
is the output current under heavy load conditions
D I
OL
is the output current under light load conditions
Energy in the capacitor is described in equation (7).
E
C
+
1
2
C V
2
(Joules)
where:
V
2
+
ƪ
ǒ
V
f
Ǔ
2
*
ǒ
V
i
Ǔ
2
ƫ
ǒ
Volts
2
Ǔ
where:
D V
f
is the final peak capacitor voltage
D V
i
is the initial capacitor voltage
Substituting equation (6) into equation (5), then substituting equation (8) into equation (7), then setting equation
(7) equal to equation (5), and then solving for C
O
yields the capacitance described in equation (9).
C
O
+
L
ƪ
ǒ
I
OH
Ǔ
2
*
ǒ
I
OL
Ǔ
2
ƫ
ƪ
ǒ
V
f
Ǔ
2
*
ǒ
V
i
Ǔ
2
ƫ
(Farads)
(5)
(6)
(7)
(8)
(9)