MP2106 – 1.5A, 15V, 800KHz SYNCHRONOUS BUCK CONVERTER

MP2106 Rev. 1.6

www.MonolithicPower.com

9

2/22/2006

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TM

Choose the compensation resistor to set the

desired crossover frequency. Determine the

value by the following equation:

FB

CS

EA

C

OUT

V

G

G

f

V

2

C

2

3

R

×

×

×

×

×

π

=

(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

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

For input voltages less than or equal to 5V, it is

recommended that an external boost diode be

added. This will help improve the regulator

efficiency. The diode can be a low cost diode

such as an IN4148 or BAT54.

MP2106

LX

BST

5V

8

6

BOOST

DIODE

10nF

MP2106_F03

Figure 3—External Boost Diode

This diode is also recommended for high duty

cycle operation (when

IN

OUT

V

V

>65%) and high

output

voltage

applications.

However, do not exceed the absolute maximum

voltage for these pins.