TPS54383, TPS54386
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SLUS774B–AUGUST 2007–REVISED OCTOBER 2007
Example 3: 5-V to 3.3V and 5-V to 1.2 V
For a low input voltage application, the TPS54386 is selected for reduced size and all ceramic output capacitors
are used. 22-µF input capacitors are selected to reduce input ripple and lead capacitors are placed in the
feedback to boost phase margin.
Figure 50. 5-V to 3.3V and 5-V to 1.2 V
80
60
180
135
90
100
90
80
70
60
50
40
30
20
V
= 1.2 V
OUT
40
V
= 3.3 V
OUT
20
45
V
= 1.2 V
OUT
0
0
-20
-40
-60
-80
-45
V
= 5 V
(V)
IN
-90
V
Gain
Phase
WIth Lead
OUT
-135
1.2
3.3
Without Lead
10
0
-180
1 k
10 k
f - Frequency -Hz
100 k
300 k
0
0.5
1.0
1.5
2.0
2.5
3.0
I
- Load Current - A
OUT
Figure 51. Efficiency vs. Load Current
Figure 52. Example 3 Loop Response
44
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