ML4865

9

DESIGN EXAMPLE

In order to design a boost converter using the ML4865,

it is necessary to define the values of a few parameters.

For this example, assume the following design

parameters:

Shutdown required

First, it must be determined whether the ML4865 is

capable of delivering the output current without an

external Schottky rectifier. This is done using Equation 1:

I

V

V

V

OUT MAX

IN

OUT

IN

()

..

.

@™

™

+

™

005

0 4

0 65

16

27

ImA

OUT MAX

()

.

..

.

.

@™

™

+

™

=

525

12

0 05 5 25

0 4

0 65 188

05

27

Next, select an inductor. As previously mentioned, the

recommended inductance is 22µH. Make sure that the

peak current rating of the inductor is at least 1.5A, and

that the DC resistance of the inductor is in the range of

110 to 220m

W. A Sumida CD75-220 meets these

requirements.

Finally, the value of the output capacitor is determined

using Equation 2:

C

L

V

H

V

F

OUT

OUT

=

™ = ™

=

10

10 22

12

18 3

m

m

.

The closest standard value would be a 22µF capacitor

with an ESR rating of 200m

W. An AVX

TPSD226M025R0200 would be a good choice.

As mentioned previously, the use of an input supply

bypass capacitor is highly recommended. Since the

output capacitance meets the minimum input

capacitance recommended it can also be used for the

input.