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100 1 M1 k 100 k10 k
-90
0
45
135
180
-45
90
270
225
Duty Cycle %
Gain Phase
10
30
50
70
90
f - Frequency -Hz
Phase - °
-20
20
40
80
100
0
60
Gain - dB
100 1M1k 100k10k
f Frequency Hz- -
-20
10
55
85
100
-5
70
25
-90
0
45
135
180
-45
90
270
225
GainPhase
10
30
50
70
90
40
Gain dB-
Phase -
°
DutyCycle%
100 1 M1 k 100 k10 k
-90
0
45
135
180
-45
90
270
225
f - Frequency -Hz
Phase - °
-20
20
40
80
100
0
60
Gain - dB
Duty Cycle %
Gain Phase
10
30
50
70
90
100 1M1k 100k10k
-90
0
45
135
180
-45
90
270
225
f Frequency Hz- -
GainPhase
10
30
50
70
90
-20
10
55
85
100
-5
70
25
40
Gain dB-
Phase -
°
DutyCycle%
Maximum Output Capacitance
TPS54383 , , TPS54386
SLUS774B – AUGUST 2007 – REVISED OCTOBER 2007
GAIN AND PHASE GAIN AND PHASE
vs vs
FREQUENCY FREQUENCY
Figure 26. TPS54383 at 600-mApp Ripple Current Figure 27. TPS54386 at 200-mApp Ripple Current
GAIN AND PHASE GAIN AND PHASE
vs vs
FREQUENCY FREQUENCY
Figure 28. TPS54386 at 400-mApp Ripple Current Figure 29. TPS54386 at 600-mApp Ripple Current
With internal pulse-by-pulse current limiting and a fixed soft start time, there is a maximum output capacitance
which may be used before startup problems begin to occur. If the output capacitance is large enough so that the
device enters a current limit protection mode during startup, then there is a possibility that the output will never
reach regulation. Instead, the TPS5438x simply shuts down and attempts a restart as if the output were
short-circuited to ground. The maximum output capacitance (including bypass capacitance distributed at the
load) is given by Equation 3 :
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