Datasheet

Cff =
3 x t
ON (max)
(R
FB1
//R
FB2
)
LM5006
SNVS646B –FEBRUARY 2011–REVISED MARCH 2013 www.ti.com
Figure 36. Efficiency vs. Load Current and V
IN
Figure 37. Efficiency vs. V
IN
LOW OUTPUT RIPPLE CONFIGURATIONS
For applications where low output ripple is required, the following options can be used to reduce or nearly
eliminate the ripple.
a) Reduced ripple configuration: In Figure 38, Cff is added across R
FB2
to AC-couple the ripple at V
OUT
directly
to the FB pin. This allows the ripple at V
OUT
to be reduced to a minimum of 25 mVp-p by reducing R3, since the
ripple at V
OUT
is not attenuated by the feedback resistors. The minimum value for Cff is determined from:
where
• t
ON(max)
is the maximum on-time, which occurs at the minimum input voltage (20)
The next larger standard value capacitor should be used for Cff.
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