MP2108 – 2A, 6V, 720KHz SYNCHRONOUS BUCK CONVERTER

INITIAL RELEASE – SPECIFICATIONS SUBJECT TO CHANGE

MP2108 Rev. 0.93

www.MonolithicPower.com

8

2/28/2006

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TM

Choose the compensation resistor to set the

desired crossover frequency. Determine the

value by the following equation:

FB

OUT

CS

EA

C

V

V

G

G

f

2

C

2

3

R

×

×

×

×

π

=

frequency (preferably 33KHz).

Choose the compensation capacitor to set the

zero below one fourth of the crossover

frequency. Determine the value by the following

equation:

C

f

3

R

2

3

C

×

×

π

>

Determine

if

the

second

compensation

capacitor, C4 is required. It is required if the

ESR zero of the output capacitor happens at

less than half of the switching frequency. Or:

1

f

R

2

C

SW

ESR

>

×

×

×

π

of the output capacitor.

If this is the case, then add the second

compensation capacitor.

Determine the value by the equation:

3

R

R

2

C

4

C

(max)

ESR

×

=

output capacitor.

External Boost Diode

It is recommended that an external boost diode

be added to help improve the regulator

efficiency. The diode can be a low cost diode

such as an IN4148 or BAT54.

MP2108

LX

BST

5V

BOOST

DIODE

10nF

1

3

MP2108_F03

Figure 3—External Boost Diode

This diode is also recommended for high duty

cycle operation (when

IN

OUT

V

V

>65%).