ncp3127 ON Semiconductor, ncp3127 Datasheet - Page 19

• Manufacturer Part Number: ncp3127
• Description: Ncp3127 2 A Synchronous Pwm Switching Converter
• Manufacturer: ON Semiconductor

C
CIN
t
V
starts to switch and a second inrush current can be
calculated:
C
C
D
I
I
t
V
is dependant on the type of load that is connected to the
output. Two types of load are considered in Figure 27: a
resistive load and a stepped current load.
DELAY_TOTAL
SS
CL
OCinrush_RMS
I
IN
OUT
LOAD
I
102 mA +
IN
OUT
OCinrush_RMS
Once the t
From the above equation, it is clear that the inrush current
ICinrush_RMS
ESR
0.316
DELAY_TOTAL
0.1 W
12 V
1 +
+
= Output capacitor
= Output capacitor ESR
= Total delay interval
= Input voltage
= Total converter output capacitance
= Total load capacitance
= Duty ratio of the load
= Applied load at the output
= RMS inrush current during start−up
= Soft−start interval
= Output voltage
CIN
C
0.316
OUT
V
5
IN
ESR
1 *
) C
0.1 W
13.64 ms
has expired, the buck converter
5
e
t
LOAD
SS
0.1W 330 mF
t
1 *
DELAY_TOTAL
CIN
13.64 ms
1
330 mF
e
ESR
V
t
DELAY_TOTAL
CIN ESR C IN
OUT
C
1
D
3
IN
) I
CL
(eq. 48)
(eq. 49)
http://onsemi.com
D
19
increase with soft−start linearly which can be quantified in
Equation 50.
R
V
I
I
Inrush Current
CLR_RMS
CR_PK
I
OUT
OUT
If the load is resistive in nature, the output current will
CLR
191 mA +
Figure 27. Load Connected to the Output Stage
_RMS +
1
3
1
3
= Output resistance
= Output voltage
= RMS resistor current
= Peak resistor current
NCP3127
3.3 V
10 W
V
R
OUT
OUT
330 mA +
I
CR_PK
+
V
R
3.3 V
10 W
OUT
OUT
OR
Load
(eq. 50)