8

ML4871

1.8

386.2

286.2

2.0

451.9

332.1

2.2

521.5

379.1

2.4

585.9

430.0

2.6

651.0

479.0

2.8

716.5

525.4

3.0

782.0

571.8

3.2

618.5

3.4

665.0

3.6

711.7

3.8

758.7

4.0

805.3

4.2

851.9

4.4

899.0

4.6

946.1

4.8

992.7

EFFICIENCY PERCENTAGE

1.0

82.0

2.0

84.4

5.0

87.0

10.0

87.6

20.0

87.9

50.0

88.3

100.0

88.6

200.0

88.2

586.0

65.1

1.0

84.4

2.0

87.0

5.0

87.7

10.0

88.4

20.0

88.9

50.0

89.1

100.0

88.9

200.0

87.5

485.0

71.6

DESIGN EXAMPLE

In order to design a boost converter using the ML4871, it

is necessary to define a few parameters. For this example,

First, it must be determined whether the ML4871 is

capable of delivering the output current. This is done using

Equation 1:

I

V

V

AA

OUT MAX

()

.

.

.

..

125

30

50

07

0 53

Next, select an inductor. As previously mentioned, the

recommended inductance is 10µH. 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 50

to 100m

W.

Finally, the value of the output capacitor is determined

using Equation 2:

C

H

V

F

™

=

44 10

50

88

m

m

.

The closest standard value would be a 100µF capacitor

with an ESR rating of 100m

W. If such a low ESR value

cannot be found, two 47µF capacitors in parallel could

also be used.

Figure 9. Typical Application Circuit

ML4871

VOUT

100µF

100µF

VIN

10µH

(Sumida CD75)

VL1

VIN

GND

DETECT

PWR GND

RESET

VL2

VOUT

The complete circuit is shown in Figure 9. As mentioned

previously, the use of an input supply bypass capacitor is

highly recommended.