Datasheet

L =
I
LR
x f
SW
x V
IN
V
OUT
x (V
IN
- V
OUT
)
LMR24220
www.ti.com SNVS737E –OCTOBER 2011–REVISED APRIL 2013
Figure 23. Maximum V
IN
for selected R
ON
L: The main parameter affected by the inductor is the amplitude of inductor current ripple (I
LR
). Once I
LR
is
selected, L can be determined by:
where
• V
IN
is the maximum input voltage and
• f
SW
is determined from Equation 2. (11)
If the output current I
OUT
is determined, by assuming that I
OUT
= I
L
, the higher and lower peak of I
LR
can be
determined. Beware that the higher peak of I
LR
should not be larger than the saturation current of the inductor
and current limits of the main and synchronous MOSFETs. Also, the lower peak of I
LR
must be positive if CCM
operation is required.
Figure 24. Inductor selection for V
OUT
= 3.3V
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