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

INITIAL RELEASE – SPECIFICATIONS SUBJECT TO CHANGE

MP2303 Rev. 0.92

www.MonolithicPower.com

11

5/2/2006

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2006 MPS. All Rights Reserved.

TM

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:

FB

OUT

CS

EA

C

V

V

G

G

f

2

C

2

3

R

×

×

×

×

π

=

34KHz.

2. Choose the compensation capacitor (C3) to

achieve

the

desired

phase

margin.

For

applications with typical inductor values, setting

the crossover frequency provides sufficient

phase margin. Determine the C3 value by the

following equation:

C

f

3

R

2

4

3

C

×

×

π

>

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 340KHz switching

frequency, or the following relationship is valid:

2

f

R

2

C

2

1

S

ESR

<

×

×

π

If this is the case, then add the optional

at the location of the ESR zero. Determine the

C6 value by the equation:

3

R

R

2

C

6

C

ESR

×

=

Soft-Start Capacitor

To reduce input inrush current during startup, a

programmable soft-start is provided by

connecting a capacitor (C4) from pin SS to

GND. The soft-start time is given by:

A

6

V

8

.

0

4

C

µ

×

=

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.

MP2303

SW

BS

10nF

5V

MP2303_F02

Figure 2—External Bootstrap Diode

This diode is also recommended for high duty

cycle operation (

IN

OUT

V

V

>65%) and high output