ncp1421 ON Semiconductor, ncp1421 Datasheet - Page 12

• Manufacturer Part Number: ncp1421
• Description: 600 Ma Sync-rect Pfm Step-up Dc-dc Converter Step-up Dc-dc Converter With True-cutoff And Ring-killer
• Manufacturer: ON Semiconductor

mF 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 mF is selected. The NCP1421 is internally compensated
for most applications, but in case additional compensation
Table 1. Suggestions for Passive Components
From the previous calculations, you need at least 18.75
16
14
12
10
8
6
4
2
0
1.4
Output Current
Figure 27. Suggested Inductance of V
500 mA
250 mA
1.6
1.8
INPUT VOLTAGE (V)
2.0
2.2
Figure 29. Suggested Capacitance for Output Capacitor
40
35
30
25
20
15
10
5
0
200
2.4
I
OUT
V
Sumida CR43, CR54,CDRH6D28 series
OUT−RIPPLE
250
= 500 mA
2.6
OUT
300
Sumida CR32 series
OUTPUT CURRENT (mA)
2.8
= 45 mV
= 3.3 V
http://onsemi.com
Inductors
350
V
OUT−RIPPLE
NCP1421
3.0
12
400
V
is required, the capacitor C4 can be used as external
compensation adjustment to improve system dynamics.
external parts for NCP1421 in different input voltage and
output current conditions, values of inductance and
capacitance are suggested in Figure 27, 28 and 29.
OUT−RIPPLE
= 40 mV
21
18
15
12
In order to provide an easy way for customers to select
450
9
6
3
0
1.6
Figure 28. Suggested Inductance of V
500
1.9
= 50 mV
550
2.2
INPUT VOLTAGE (V)
600
2.5
25
33
50
100
2.8
Panasonic ECJ series
Panasonic ECJ series
Kemet TL494 series
Kemet TL494 series
Capacitors
3.1
I
OUT
3.4
= 500 mA
OUT
3.7
= 5.0 V
4.0