MP2363DN Monolithic Power Systems, MP2363DN Datasheet - Page 7

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

Choose a diode whose maximum reverse voltage
rating is greater than the maximum input voltage,
and whose current rating is greater than the
maximum load current. Table 2 lists example
Schottky diodes and manufacturers.
Input Capacitor
The input current to the step-down converter is
discontinuous, therefore a capacitor is required
to supply the AC current to the step-down
converter while maintaining the DC input
voltage. Use low ESR capacitors for the best
performance. Ceramic capacitors are preferred,
but tantalum or low-ESR electrolytic capacitors
may also suffice.
Since the input capacitor (C1) absorbs the input
switching current it requires an adequate ripple
current rating. The RMS current in the input
capacitor can be estimated by:
I
voltage, and V
case condition occurs at V
For simplification, choose the input capacitor
whose RMS current rating greater than half of
the maximum load current.
MP2363 Rev. 1.0
6/15/2006
LOAD
MBRS330
MBRS340
Diode
SK33
SK34
B330
B340
is the load current, V
Table 2—Diode Selection Guide
I
C
1
Voltage/Current
=
IN
I
LOAD
is the input voltage. The worst-
30V, 3A
40V, 3A
30V, 3A
40V, 3A
30V, 3A
40V, 3A
Rating
I
C
×
1
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
=
V
I
V
LOAD
OUT
IN
2
IN
×
= 2V
⎛
⎜
⎜
⎝
Manufacture
Diodes Inc.
Diodes Inc.
Diodes Inc.
Diodes Inc.
On Semiconductor
On Semiconductor
1
OUT
−
V
OUT
V
OUT
IN
is the output
, where:
⎞
⎟
⎟
⎠
© 2006 MPS. All Rights Reserved.
www.MonolithicPower.com
MP2363 – 3A, 27V, 365KHz STEP-DOWN CONVERTER
The input capacitor can be electrolytic, tantalum
or ceramic. When using electrolytic or tantalum
capacitors, a small, high quality ceramic
capacitor, i.e. 0.1µF, should be placed as close
to the IC as possible. When using ceramic
capacitors, make sure that they have enough
capacitance to provide sufficient charge to
prevent excessive voltage ripple at input. The
input voltage ripple caused by capacitance can
be estimated by:
Output Capacitor
The output capacitor (C2) is required to
maintain the DC output voltage. Ceramic,
tantalum or low ESR electrolytic capacitors are
recommended.
preferred to keep the output voltage ripple low.
The output voltage ripple can be estimated by:
Where L is the inductor value and R
equivalent series resistance (ESR) value of the
output capacitor.
In
impedance at the switching frequency is
dominated by the capacitance. The output
voltage
capacitance. For simplification, the output
voltage ripple can be estimated by:
In
capacitors, the ESR dominates the impedance
at the switching frequency. For simplification,
the output ripple can be approximated to:
The characteristics of the output capacitor also
affect the stability of the regulation system. The
MP2363 can be optimized for a wide range of
capacitance and ESR values.
∆
V
OUT
the
the
=
∆V
∆
f
∆V
V
ripple
S
case
OUT
case
V
OUT
IN
×
OUT
L
=
=
×
f
=
I
S
8
LOAD
⎛
⎜ ⎜
⎝
1
of
f
×
V
×
of
S
is
Low
OUT
−
C
f
×
S
1
V
V
L
2
V
×
ceramic
OUT
OUT
mainly
tantalum
×
×
IN
V
L
⎛
⎜
⎝
V
OUT
1
ESR
×
IN
⎞
⎟ ⎟
⎠
−
×
C
V
2
×
⎛
⎜
⎜
⎝
V
OUT
R
⎛
⎜ ⎜
⎝
×
IN
1
ESR
caused
⎛
⎜ ⎜
⎝
−
capacitors,
capacitors
1
⎞
⎟
⎠
or
−
×
V
+
V
OUT
R
V
IN
V
8
ESR
OUT
IN
electrolytic
×
⎞
⎟ ⎟
⎠
ESR
f
S
by
⎞
⎟ ⎟
⎠
1
×
is the
C
2
are
the
the
⎞
⎟
⎟
⎠
7