Datasheet

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Input Capacitor
RIPPLE RIPPLE IN _ PEAK(max)
I I I= D
0 2
RIPPLE
I .D =
0 2 6 39 1 28
RIPPLE
I . . A . A= ´ =
IN _ RIPPLE(max) RIPPLE _ IN IN _ RECTIFIED(min)
V V V= D
0 06
RIPPLE _ IN
V .D =
2
IN _ RECTIFIED IN
V V=
2 85 120 2
IN _ RECTIFIED(min)
V V . V= ´ =
0 06 120 2 7 21
IN _ RIPPLE(max)
V . . V . V= ´ =
8
RIPPLE
IN
SW IN _ RIPPLE(max)
I
C
f V
=
1 28
0 341
8 65 7 21
IN
. A
C . F
kHz . V
m= =
´ ´
UCC28019
SLUS755B – APRIL 2007 – REVISED DECEMBER 2007
Note that the UCC28019 is a continuous conduction mode controller and as such the inductor ripple current
should be sized accordingly. Allowing an inductor ripple current, I
RIPPLE
, of 20% and a high frequency voltage
ripple factor, V
RIPPLE_IN
, of 6%, the maximum input capacitor value, C
IN
, is calculated by first determining the input
ripple current, I
RIPPLE
, and the input voltage ripple, V
IN_RIPPLE(max)
:
The value for the input x-capacitor can now be calculated:
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Product Folder Link(s): UCC28019