Datasheet
PTN78060W
2 6
5
+
7 4
Rset
GND Adjust
Sense
A BC
13
GNDGND
UDG−05086
V
O
V
I
V
O
V
I
Inhibit
C1
1 µF
50 V
Ceramic
C2
2.2 µF
50 V
Ceramic
(Required)
C3
100 µF
(Required)
C4
2.2 µF
Ceramic
R
SET
π Filters
PTN78060W , PTN78060H
SLTS229B – NOVEMBER 2004 – REVISED JUNE 2009 ...................................................................................................................................................
www.ti.com
A. See specifications for required value and type. For PTN78060H, C
C2
= 3 × 4.7 µ F.
B. See Application Information section for suggested value and type.
C. For PTN78060H, C
C1
≥ 4.7 µ F.
Figure 32. Adding High-Frequency Bypass Capacitors To The Input and Output
If a further reduction in ripple/noise level is required for an application, higher order filters must be used. A π (pi)
filter, employing a ferrite bead (Fair-Rite part number 2673000701 or equivalent) in series with the input or output
terminals of the regulator reduces the ripple/noise by at least 20 db (see Figure 33 and Figure 34 ). In order for
the inductor to be effective ceramic capacitors are also required. (Note: see Capacitor Recommendations for
additional information on vendors and component suggestions.)
These inductors plus ceramic capacitors form an excellent filter because of the rejection at the switching
frequency (650 kHz - 1 MHz). The placement of this filter is critical. It must be located as close as possible to the
input or output pins to be effective. The ferrite bead is small (12,5 mm × 3 mm), easy to use, low cost, and has
low dc resistance. Fair-Rite also manufactures a surface-mount bead (part number 2773021447). It is rated to 5
A, and can be used on the output bus. As an alternative, suitably rated 1- µ H to 5- µ H wound inductors can be
used in place of the ferrite inductor bead.
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