MP2363DN Monolithic Power Systems, MP2363DN Datasheet - Page 9

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

To optimize the compensation components for
conditions not listed in Table 2, the following
procedure can be used.
1. Choose the compensation resistor (R3) to set
the desired crossover frequency. Determine the
R3 value by the following equation:
Where f
(which typically has a value no higher than
37.5KHz).
2. Choose the compensation capacitor (C3) to
achieve
applications with typical inductor values, setting
the compensation zero, f
the crossover frequency provides sufficient
phase margin. Determine the C3 value by the
following equation:
3. Determine if the second compensation
capacitor (C6) is required. It is required if the
ESR zero of the output capacitor is located at
less than half of the 365KHz switching
frequency, or the following relationship is valid:
If this is the case, then add the second
compensation capacitor (C6) to set the pole f
at the location of the ESR zero. Determine the
C6 value by the equation:
MP2363 Rev. 1.0
6/15/2006
C
the
is the desired crossover frequency
R
3
2
=
desired
C
π
C
3
2
×
G
6
π
C
>
EA
=
×
2
1
2
C
C
×
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
×
π
2
2
R
G
×
×
×
ESR
R
R
CS
Z1
phase
4
f
R
3
3
C
, below one forth of
ESR
×
×
<
f
C
V
f
V
2
S
OUT
FB
margin.
© 2006 MPS. All Rights Reserved.
www.MonolithicPower.com
For
MP2363 – 3A, 27V, 365KHz STEP-DOWN CONVERTER
P3
Soft-Start Capacitor
To reduce input inrush current during startup, a
programmable
connecting a capacitor (C4) from pin SS to
GND. The soft-start time is given by:
To reduce the susceptibility to noise, do not
leave SS pin open. Use a capacitor with small
value if you do not need soft-start function.
External Bootstrap Diode
It is recommended that an external bootstrap
diode be added when the system has a 5V
fixed input or the power supply generates a 5V
output. This helps improve the efficiency of the
regulator. The bootstrap diode can be a low
cost one such as IN4148 or BAT54.
This diode is also recommended for high duty
cycle operation (when
output voltage (V
Figure 2—External Bootstrap Diode
t
SS
MP2363
(
ms
OUT
soft-start
)
>12V) applications.
=
SW
BS
45
1
3
V
×
V
OUT
C
IN
SS
is
5V
DIODE
10nF
>65%) and high
(
µ
) F
provided
by
9