Datasheet

LT1933
10
1933fe
APPLICATIONS INFORMATION
Figure 1 shows the transient response of the LT1933 with
several output capacitor choices. The output is 3.3V. The
load current is stepped from 100mA to 400mA and back to
100mA, and the oscilloscope traces show the output volt-
age. The upper photo shows the recommended value. The
second photo shows the improved response (less voltage
drop) resulting from a larger output capacitor and a phase
lead capacitor. The last photo shows the response to a high
performance electrolytic capacitor. Transient performance
is improved due to the large output capacitance, but output
ripple (as shown by the broad trace) has increased because
of the higher ESR of this capacitor.
Figure 1. Transient Load Response of the LT1933 with Different
Output Capacitors as the Load Current is Stepped from 100mA
to 400mA. V
IN
= 12V, V
OUT
= 3.3V, L = 22μH.
22µFFB
16.5k
10k
V
OUT
1933 F01a
V
OUT
50mV/DIV
I
OUT
200mA/DIV
V
OUT
50mV/DIV
I
OUT
200mA/DIV
FB
V
OUT
1933 F01b
16.5k
10k
22µF
2x
470pF
V
OUT
50mV/DIV
I
OUT
200mA/DIV
SANYO
4TPB100M
FB
1933 F01c
V
OUT
+
16.5k
10k
100µF
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