ncp3121 ON Semiconductor, ncp3121 Datasheet - Page 15

• Manufacturer Part Number: ncp3121
• Description: Dual 3.0 A, Step-down Dc/dc Switching Regulator
• Manufacturer: ON Semiconductor

Output Rectifier Diode
magnetic field in the inductor. During off time, the internal
MOSFET switch is off. Since the current in the inductor has
to discharge, the current flows through the rectifying diode
to the output. A Schottky diode is recommended due to low
diode forward voltage and very short recovery times, which
positively impacts the step down voltage converter's overall
efficiency. Another choice could be fast recovery or
ultra-fast recovery diodes. It should be noted that some
types of these diodes with an abrupt turn-off characteristic
may cause instability or EMI troubles.
Table 2. Inductor Examples
When the high-side switch is on, energy is stored in the
L [mH]
8.2
6.8
5.6
5.0
3.3
33
22
15
10
9
MSS1246T-223
MSS1260T-153
DO5010H-333
PF0382.333NL
PF0552.333NL
PF0382.223NL
MSS1278-333
DO3316P-153
DO3340P-103
DO3316P-103
MSS1246-822
DO5022P-562
MSS7341-502
DO3316P-332
DS5022P-223
DS5022P-103
DS3316T-822
DO33165-562
DS5022P-332
P0751.153NL
P0751.103NL
Part Number
P1169.123NL
P0648.223
74458133
74458122
74459010
74456068
74456056
74459115
74458115
7445610
Non-shielded
Shielded/
N
N
S
N
S
S
N
N
S
N
N
N
S
S
N
N
S
N
S
N
N
S
N
S
N
N
N
S
S
S
S
http://onsemi.com
I
rms
3.14
4.15
4.67
4.65
3.0
3.1
3.1
3.0
3.7
3.1
3.3
3.5
3.5
3.1
3.0
3.5
3.5
4.0
3.5
3.9
3.3
3.9
3.5
3.8
3.5
3.8
4.0
4.1
4.7
4.7
3.3
NCP3121
[A]
15
voltage. The peak conducting current is clamped by the
current limit of the NCP3121. Use of Schottky barrier diodes
reduces diode reverse recovery input current spikes. For
switching regulators operating at low duty cycles, it is
beneficial to use rectifying diodes with somewhat higher
RMS current ratings (thus lower forward voltages). This is
because the diode conduction interval is much longer than
that of the transistor. Converter efficiency will be improved
if the voltage drop across the diode is lower. The average
current can be calculated from:
DCR max [mW}
The peak reverse voltage is equal to the maximum input
54.1
66
65
80
66
59
61
47
70
47
46
46
40
48
36
40
42
45
40
34
38
37
32
35
34
21
32
24
26
39
3
I
D(AVG)
Manufacturer
+
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