TM
MP2303 – 3A, 28V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER
INITIAL RELEASE – SPECIFICATIONS SUBJECT TO CHANGE
In this case, a third pole set by the optional
compensation capacitor (C6) and the
compensation resistor (R3) is used to
compensate the effect of the ESR zero on the
loop gain. This pole is located at:
f
P 3
=
1
2
π ×
C6
×
R3
Table 3—Compensation Values for Typical
Output Voltage/Capacitor Combinations
V
OUT
1.8V
2.5V
3.3V
5V
12V
1.8
2.5V
3.3V
5V
2.5V
3.3V
5V
12V
L
4.7µH
4.7µH -
6.8µH
6.8µH -
10µH
10µH -
15µH
15µH -
22µH
4.7µH
4.7µH -
6.8µH
6.8µH -
10µH
10µH -
15µH
4.7µH -
6.8µH
6.8µH -
10µH
10µH -
15µH
15µH -
22µH
C2
100µF
Ceramic
47µF Ceramic
22µFx2
Ceramic
22µFx2
Ceramic
22µFx2
Ceramic
100µF/100mΩ
SP-CAP
47µF
SP-CAP
47µF
SP-CAP
47µF
SP CAP
560µF Al.
30mΩ ESR
560µF Al.
30mΩ ESR
470µF Al.
30mΩ ESR
220µF Al.
30mΩ ESR
R3
5.6kΩ
3.65kΩ
4.42kΩ
6.98kΩ
16.5kΩ
8.4kΩ
5.6kΩ
6.8kΩ
10kΩ
10kΩ
10kΩ
15kΩ
15kΩ
C3
5.6nF
8.2nF
4.7nF
3.3nF
1.8nF
2.2nF
3.3nF
2.2nF
2.2nF
12nF
10nF
8.2nF
10nF
C6
None
None
None
None
None
None
None
None
None
1.8nF
1.5nF
1nF
390pF
The goal of compensation design is to shape
the converter transfer function to get a desired
loop gain. The system crossover frequency
where the feedback loop has the unity gain is
important.
Lower crossover frequencies result in slower
line and load transient responses, while higher
crossover frequencies could cause system
instability. A good rule of thumb is to set the
crossover frequency to approximately one-tenth
of the switching frequency. Switching frequency
for the MP2303 is 340KHz, so the desired
crossover frequency is 34KHz.
Table 3 lists the typical values of compensation
components for some standard output voltages
with various output capacitors and inductors. The
values of the compensation components have
been optimized for fast transient responses and
good stability at given conditions.
MP2303 Rev. 0.92
5/2/2006
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