Fairchild SEMICONDUCTOR RC5051 User Manual
Page 20
AN50
APPLICATION NOTE
20
Input Ripple and Power on Input Rush Current
Note:
Excellent input ripple voltage. Input ripple voltage is recom-
mended to be less than 5% of the output voltage.
Power on Input Rush Current was not measured on the moth-
erboard because we did not want to cut the 5V trace and
insert a current probe in series with the supply. However,
with the input filter design, the Input Rush Current is well
within specification.
I
load
= 9.9A
Input Ripple
Voltage = 15mV
Refer to Attach-
ment G for Scope
Picture
Component Case Temperature
Note:
The values for case temperatures are within guidelines. That is, case temperatures for all components should be below
105
°
C @25
°
C Ambient.
Device
Description
Case Temperature
I
load
= 9.9A
(
°
C)
Case Temperature
I
load
= 12.4A
(
°
C)
Case Temperature
I
load
= 13.9A
(
°
C)
Q3A
MOSFET
K1388
57
63
66.3
Q3B
MOSFET
K1388
58
64
66.6
L1
Inductor,
Unknown
53
56
61.2
Q2
Schottky Diode
2048CT
66
70
87
IC
Raytheon’s RC5050
52
54
58
Cin
Input Cap. 1000
µ
F
38.2
36.8
39
Cout
Output Cap.
1500
µ
F
35
34.8
38.2
Evaluation Summary
The on-board DC-DC converter is fully functional. It has
excellent load regulation, transient response, and input volt-
age ripple.
Attachment A
Attachment B