Datasheet

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