Datasheet

 
 
 
SLVS519A − MAY 2004 − REVISED OCTOBER 2004
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15
Conditions are V
I
= 12 V, V
O
= 3.3 V, f
s
= 500 kHz, I
O
= 3 A, T
A
= 25 °C, unless otherwise noted
Figure 14
V
I
= 5 V/div
V
O
= 2 V/div
V
(PWRGD)
= 2 V/div
POWER DOWN
Time − 2 ms/div
Power Down Waveforms − V
See Figure 25
Figure 15
50
55
60
65
70
75
80
85
90
95
100
01234
V
I
= 18 V
I
O
− Output Current − A
Efficiency − %
EFFICIENCY
vs
OUTPUT CURRENT
V
I
= 12 V
V
I
= 6 V
See Figure 26
Figure 16
I
(L1)
= 200 mA/div
V
(PH)
= 5 V/div
CONTINUOUS CONDUCTION MODE
Time − 1 µs/div
Continuous Conduction Mode
See Figure 26
Figure 17
I
(L1)
= 200 mA/div
V
(PH)
= 5 V/div
LIGHT LOAD CONDUCTION
Time − 1 µs/div
Light Load Conduction
See Figure 26
Figure 18
V
I
= 10 V/div
V
O1(3.3)
= 2 V/div
V
(PWRGD1)
= 2 V/div
SEQUENCING WAVEFORMS
Time − 2 ms/div
Sequencing Waveforms − V
V
O2 (1.8)
= 2 V/div
See Figure 27
Figure 19
V
(PH1)
= 10 V/div
V
I
= 50 mV/div (ac coupled)
INPUT RIPPLE CANCELLATION
Time − 1 µs/div
Input Ripple Cancellation − V
V
(PH2)
= 10 V/div
See Figure 27
Figure 20
−60
−50
−40
−30
−20
−10
0
10
20
30
40
50
60
100 1 k 10 k 100 k 1 M
−180
−150
−120
−90
−60
−30
0
30
60
90
120
150
180
Phase
Gain
f − Frequency − Hz
G − Gain − dB Phase − Degrees
MEASURED LOOP RESPONSE
100 mF POSCAP
See Figure 28
Figure 21
−60
−50
−40
−30
−20
−10
0
10
20
30
40
50
60
100 1 k 10 k 100 k 1 M
−180
−150
−120
−90
−60
−30
0
30
60
90
120
150
180
Phase
Gain
f − Frequency − Hz
G − Gain − dB Phase − Degrees
MEASURED LOOP RESPONSE
2 x 180 mF SP CAPACITORS
See Figure 29
Figure 22
−60
−50
−40
−30
−20
−10
0
10
20
30
40
50
60
100 1 k 10 k 100 k 1 M
−180
−150
−120
−90
−60
−30
0
30
60
90
120
150
180
Phase
Gain
f − Frequency − Hz
G − Gain − dB Phase − Degrees
MEASURED LOOP RESPONSE
330 mF OSCON
See Figure 30