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SLVS456C − OCTOBER 2003 − REVISED OCTOBER 2004
EFFICIENCY
vs
OUTPUT CURRENT
POWER DOWN
CONTINUOUS CONDUCTION MODE
100
95
90
85
80
75
70
65
60
55
50
V
= 5 V/div
I
V = 6 V
I
V
= 2 V/div
O
V
= 5 V/div
(PH)
V = 12 V
I
V
= 2 V/div
(PWRGD)
V = 18 V
I
I
= 0.5 A/div
(Inductor)
V
= 3.3 V
= 500 kHz
O
f
S
See Figure 24
See Figure 25
See Figure 25
Time − 2 ms/div
0.0
0.5
1.0
1.5
2.0 2.5 3.0
Time − 1 µs/div
I
− Output Current − A
O
Figure 14
Figure 15
Figure 16
DISCONTINUOUS CONDUCTION MODE
INPUT RIPPLE CANCELLATION
SEQUENCING WAVEFORMS
V
= 10 V/div
(PH1)
V
= 10 V/div
I
V
= 2 V/div
O1
V
= 10 V/div
(PH2)
V
= 5 V/div
(PH)
V
= 2 V/div
= 2 V/div
(PWRGD)
V
= 100 mV/div (ac coupled)
I(Ripple)
V
O2
I
= 0.5 A/div
V = 1.8 V, 3.3 V
See Figure 26
(Inductor)
VIN = 12 V, V
= 1.8 V,
O1
See Figure 25
V
= 3.3 V, See Figure 26
O2
Time − 1 µs/div
Time − 1 µs/div
Time − 2 ms/div
Figure 17
Figure 18
Figure 19
EFFICIENCY
vs
OUTPUT CURRENT
100
95
90
85
80
75
70
65
60
55
50
V
V
= 5 V
I
= −5 V
O
f
= 250 kHz
S
See Figure 27
0.0
0.5
1.0
1.5 2.0
I
− Output Current − A
O
Figure 20
12
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