L4978 Datasheet, PDF (9/12 Pages) STMicroelectronics – 2A STEP DOWN SWITCHING REGULATOR

Figure 21. Load transient.
L4978
Figure 22. Line transient.
V_CC
(V)
30
D97IN786
20
10
1
V_O
(mV)
I_O = 1A
f_sw = 100KHz
100
2
0
1ms/DIV
-100
Figure 23. Soft start capacitor selection Vs in-
ductor and Vccmax.
L
(µH)
fsw=100KHz
680nF
D97IN745
470nF
400
330nF
300
200
220nF
100
100nF
0
15 20 25 30 35 40 45 50 V_CCmax(V)
Figure 25. Open loop frequency and phase of er-
ror amplifier
GAIN
(dB)
D97IN787
Phase
50
GAIN
0
0
-50
45
-100
-150
Phase
90
135
-200
10 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷ 10⁸ f(Hz)
Figure 24. Soft start capacitor selection vs. In-
ductor and Vccmax.
L
(µH)
fsw=200KHz
D97IN746
56nF
300
47nF
200
33nF
22nF
100
0
15 20 25 30 35 40 45 50 V_CCmax(V)
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