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RC5050
PRODUCT SPECIFICATION
8
Table 3. RC5050 Application Bill of Materials for Intel Pentium II Processors
Notes:
1. In order to meet the voltage transient requirements for the Intel Pentium II Motherboard application, the equivalent ESR of the
output capacitors must not exceed 7.5m
W
. In order to satisfy the specified Output Voltage Regulation requirements for
V
OUT
= 1.8V at 15A for next generation processors, the output capacitors must exhibit no more than 6.0m
W
equivalent ESR
for a motherboard application. The use of the capacitors recommended in Table 1 will address this and other voltage
specifications without significant added cost, although it is left up to the user to specify the components used. Please refer to
Application Bulletin 5 for additional considerations required to meet the Intel Pentium II voltage transient specifications.
2. To optimize a converter for 15A at 1.8V output, f
SW
= 300 kHz, change the value of L1 to 1.24
m
H.
3. Inductor L2 is recommended to isolate the 5V input supply from current surges caused by MOSFET switching. L2 is not
required for normal operation and may be omitted if desired.
4. For 15A designs using IR3103 MOSFETs, heat sinks with thermal resistance
Q
SA
< 50
°
C/W should be used.
Reference
C4, C5, C7–C11
Manufacturer Part #
Panasonic
ECU-V1H104ZFX
Panasonic
ECU-V1H121JCG
Panasonic
ECSH1CY105R
Sanyo
10MV1200EG
Sanyo
6MV1500GX
Motorola MBR2015CT
1N4735A
Description
0.1
m
F 50V capacitor
Requirements/Comments
Cext
100pF capacitor
C12, C6
1
m
F 16V capacitor
C
IN
1200
m
F 10V electrolytic
capacitor 10mm x 20mm
1500
m
F 6.3V electrolytic
capacitor 10mm x 20mm
Schottky Diode
6.2V Zener Diode,
Motorola
1.3
m
H, 14A inductor
DCR ~ 2.5m
W
2.5
m
H, 11A inductor
DCR ~ 6m
W
N-Channel Logic Level
Enhancement Mode MOSFET
ESR < 62m
W
See Table 2
ESR < 44m
W
See Note 1 and Table 2
V
f
< 0.52 at I
f
= 10A
C
OUT
DS1
D1
L1
Skynet
320-8107
Skynet
320-6110
International Rectifier
IRL3103
See Note 2
L2
See Note 3
M1, M2
R
DS(ON)
< 19m
W
V
GS
< 4.5V, I
D
= 15A
See Note 4
R
SENSE
Copel
AWG#18
Panasonic
ERJ-6GEY050Y
Panasonic
ERJ-6ENF10.0KV
5.5m
W
CuNi Alloy Wire Resistor
R5
47
W
5% resistor
R6
10K
W
5% resistor
Application Information
Simple Step-Down Converter
Figure 3. Simple Buck DC-DC Converter
Figure 3 illustrates a step-down DC-DC converter with no
feedback control. The derivation of the basic step-down
converter will serve as a basis for the design equations for
the RC5050. Referring to Figure 3, the basic operation
begins by closing the switch S1. When S1 is closed, the input
voltage V
IN
is impressed across inductor L1. The current
flowing in this inductor is given by the following equation:
where T
ON
is the duty cycle (the time when S1 is closed).
C1
R
L
Vout
+
–
D1
V
IN
65-5050-06
L1
S1
I
L
V
--------------–
V
L1
(
)
T
ON
=