NB650/NB650H – 6A, 28V, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER
ramp is not needed. A minimum ESR value of
and/or lower saturation current. To determine the
inductor value, allow the inductor peak-to-peak
ripple current to reach approximately 30% to 40%
of the maximum switch current limit. Make sure
that the peak inductor current is below the
maximum switch current limit. The inductance
value can be calculated as:
12mꢀ is required to ensure stable operation of
the converter. For simplification, the output ripple
can be approximated as:
VOUT
V
ΔVOUT
=
×(1− OUT )×RESR
(32)
fSW ×L
V
IN
Inductor
VOUT
VOUT
L =
×(1−
)
(33)
The inductor supplies constant current to the
output load while being driven by the switching
input voltage. A larger value inductor results in
less ripple current, which results in lower output
ripple voltage. However, a larger value inductor is
physically larger, has a higher series resistance,
fSW × ΔIL
V
IN
Where ΔIL is the peak-to-peak inductor ripple cur
rent.
Choose an inductor that will not saturate under
the maximum inductor peak current. The peak
inductor current can be calculated as:
VOUT
VOUT
ILP = IOUT
+
×(1−
)
(34)
2fSW ×L
V
IN
NB650/NB650H Rev. 1.1
10/11/2012
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