Datasheet

NCP1422
http://onsemi.com
12
From the previous calculations, you need at least 18.75
F in order to achieve the specified ripple level at the
conditions stated. Practically, a capacitor that is one level
larger is used to accommodate factors not taken into
account in the calculations. Therefore, a capacitor value of
22 F is selected. The NCP1422 is internally compensated
for most applications, but in case additional compensation
is required, the capacitor C4 can be used as external
compensation adjustment to improve system dynamics.
In order to provide an easy way for customers to select
external parts for NCP1422 in different input voltage and
output current conditions, values of inductance and
capacitance are suggested in Figures 24, 25 and 26.
0
2
4
6
8
10
12
1.8 2.0 2.2
2.4
2.6 2.8 3.0
Figure 24. Suggested Inductance of V
OUT
= 3.3 V Figure 25. Suggested Inductance of V
OUT
= 5.0 V
Figure 26. Suggested Capacitance for Output Capacitor
INPUT VOLTAGE (V)
INDUCTOR VALUE (H)
I
OUT
= 700 mA
0
3
6
9
12
2.2 2.5 2.8 3.1 3.4 3.7 4.0
INPUT VOLTAGE (V)
INDUCTOR VALUE (H)
OUTPUT CURRENT (mA)
CAPACITOR VALUE (F)
40
35
30
25
20
15
10
5
0
100 200 300 400 500 600 700 800
I
OUT
= 700 mA
25
33
50
100
CAPACITOR ESR (m)
V
OUT−RIPPLE
= 45 mA
Table 1. Suggestions for Passive Components
Output Current Inductors Capacitors
800 mA Sumida CR43, CR54,CDRH6D28 series Panasonic ECJ series
Kemet TL494 series
250 mA Sumida CR32 series Panasonic ECJ series
Kemet TL494 series