Datasheet

SW
FB
V
OUT
R2
LM25010
R1
C2
L1
CB
CARA
SW
FB
LM25010
V
OUT
Cff
R2
L1
R1
C2
R3
FB
SW
L1
C2
R3
LM25010
R1
R2
V
OUT
LM25010
SNVS419D –DECEMBER 2005–REVISED FEBRUARY 2013 www.ti.com
Figure 15. Low Ripple Output
Where the circuit of Figure 15 is not suitable, the circuits of Figure 16 or Figure 17 can be used.
Figure 16. Low Output Ripple Using a Feedforward Capacitor
In Figure 16, Cff is added across R1 to AC-couple the ripple at V
OUT
directly to the FB pin. This allows the ripple
at V
OUT
to be reduced, in some cases considerably, by reducing R3. In the circuit of Figure 12, the ripple at V
OUT
ranged from 50 mV
P-P
at V
IN
= 6V to 285 mV
P-P
at V
IN
= 40V. By adding a 1000 pF capacitor at Cff and reducing
R3 to 0.75Ω, the V
OUT
ripple was reduced by 50%, ranging from 25 mV
P-P
to 142 mV
P-P
.
Figure 17. Low Output Ripple Using Ripple Injection
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