MP2363DN Monolithic Power Systems, MP2363DN Datasheet - Page 6

• Manufacturer Part Number: MP2363DN
• Description: 3A, 27V, 365khz Step-down Converter
• Manufacturer: Monolithic Power Systems

APPLICATION INFORMATION
COMPONENT SELECTION (Refer to the
Typical Application Circuit on page 10)
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB
pin. The voltage divider divides the output
voltage down to the feedback voltage by the
ratio:
Where V
the output voltage.
Thus the output voltage is:
A typical value for R2 can be as high as 100kΩ,
but a typical value is 10kΩ. Using that value, R1
is determined by:
Inductor
The inductor is required to supply constant
current to the output load while being driven by
the switched input voltage. A larger value
inductor will result in less ripple current that will
result in lower output ripple voltage. However,
the larger value inductor will have a larger
physical size, higher series resistance, and/or
lower saturation current. A good rule for
determining the inductance to use is to allow
the peak-to-peak ripple current in the inductor
to be approximately 30% of the maximum
switch current limit. Also, make sure that the
peak inductor current is below the maximum
switch current limit. The inductance value can
be calculated by:
Where V
switching frequency, and ∆I
peak inductor ripple current.
MP2363 Rev. 1.0
6/15/2006
IN
FB
is the input voltage, f
R
is the feedback voltage and V
1
L
=
V
=
V
. 8
OUT
FB
f
18
S
V
×
OUT
=
=
×
∆I
. 0
V
(
V
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
OUT
L
92
OUT
×
×
⎛
⎜ ⎜
⎝
R
1
−
R
1
−
R
1
. 0
+
R
V
2
+
R
92
V
L
2
OUT
R
IN
2
)(
S
is the peak-to-
2
k
is the 365KHz
⎞
⎟ ⎟
⎠
Ω
)
© 2006 MPS. All Rights Reserved.
www.MonolithicPower.com
OUT
MP2363 – 3A, 27V, 365KHz STEP-DOWN CONVERTER
is
Choose an inductor that will not saturate under
the maximum inductor peak current. The peak
inductor current can be calculated by:
Where I
365KHz switching frequency.
Table 1 lists a number of suitable inductors
from various manufacturers. The choice of
which style inductor to use mainly depends on
the price vs. size requirements and any EMI
requirement.
Output Rectifier Diode
The output rectifier diode supplies the current to
the inductor when the high-side switch is off. To
reduce losses due to the diode forward voltage
and recovery times, use a Schottky diode.
Sumida
CDRH5D28 Shielded
CDRH5D28 Shielded
CDRH6D28 Shielded
CDRH104R Shielded
Toko
Coilcraft
Vendor/
DO3308
DO3316
CDH74
Type A
D53LC
D104C
D10FL
Model
CR75
D75C
Table 1—Inductor Selection Guide
LOAD
I
LP
=
Shielded
Shielded
Shielded
I
is the load current and f
LOAD
Open
Open
Open
Open
Open
Core
Type
+
2
×
V
OUT
f
Material
S
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Core
×
L
×
⎛
⎜ ⎜
⎝
1
−
10.1 10.0 3.0
10.0 10.0 4.3
7.0
7.3
5.5
5.5
6.7
5.0
7.6
9.7
9.4 13.0 3.0
9.4 13.0 5.1
V
W
V
Dimensions
OUT
IN
Package
(mm)
⎞
⎟ ⎟
⎠
7.8
8.0
5.7
5.7
6.7
5.0
7.6
1.5
L
S
is the
5.5
5.2
5.5
5.5
3.0
3.0
5.1
4.0
H
6