MP2303 – 3A, 28V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER

INITIAL RELEASE – SPECIFICATIONS SUBJECT TO CHANGE

MP2303 Rev. 0.92

www.MonolithicPower.com

10

5/2/2006

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2006 MPS. All Rights Reserved.

TM

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:

3

R

6

C

2

1

P

×

×

π

=

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.

Table 3—Compensation Values for Typical

Output Voltage/Capacitor Combinations

L

C2

R3

C3

C6

1.8V

4.7µH

100µF

Ceramic

5.6kΩ

5.6nF

None

2.5V

4.7µH -

6.8µH

47µF Ceramic

3.65kΩ 8.2nF

None

3.3V

6.8µH -

10µH

22µFx2

Ceramic

4.42kΩ 4.7nF

None

5V

10µH -

15µH

22µFx2

Ceramic

6.98kΩ 3.3nF

None

12V

15µH -

22µH

22µFx2

Ceramic

16.5kΩ 1.8nF

None

1.8

4.7µH

100µF/100mΩ

SP-CAP

8.4kΩ

2.2nF

None

2.5V

4.7µH -

6.8µH

47µF

SP-CAP

5.6kΩ

3.3nF

None

3.3V

6.8µH -

10µH

47µF

SP-CAP

6.8kΩ

2.2nF

None

5V

10µH -

15µH

47µF

SP CAP

10kΩ

2.2nF

None

2.5V

4.7µH -

6.8µH

560µF Al.

30mΩ ESR

10kΩ

12nF

1.8nF

3.3V

6.8µH -

10µH

560µF Al.

30mΩ ESR

10kΩ

10nF

1.5nF

5V

10µH -

15µH

470µF Al.

30mΩ ESR

15kΩ

8.2nF

1nF

12V

15µH -

22µH

220µF Al.

30mΩ ESR

15kΩ

10nF

390pF