MP2482 – 5A, 30V, 420kHZ STEP-DOWN CONVERTER

MP2482 Rev.1.4

www.MonolithicPower.com

10

9/21/2011

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

Preliminary Specifications Subject to Change

© 2011 MPS. All Rights Reserved.

APPLICATION INFORMATION

The schematic on the front page shows a typical

MP2482 application. The IC can provide up to 5A

output current at a nominal output voltage of 3.3V.

For proper thermal performance, the exposed pad

of the device must be soldered down to the

printed circuit board.

Setting the Output Voltage

The external resistor divider is used to set the

output voltage (see the schematic on front page).

The feedback resistor R1 also sets the feedback

loop bandwidth with the internal compensation

capacitor (see Figure 1). Choose R1 to be

around 40.2kΩ for optimal transient response. R2

is then given by:

1

V

8

.

0

V

1

R

2

R

=

Table 1—Resistor Selection for Common

Output Voltages

R1 (kΩ)

R2 (kΩ)

1.8

40.2 (1%)

32.4 (1%)

2.5

40.2 (1%)

19.1 (1%)

3.3

40.2 (1%)

13 (1%)

5

40.2 (1%)

7.68 (1%)

Selecting the Inductor

A 1µH to 10µH inductor with a DC current rating

of at least 25% percent higher than the maximum

load

current

is

recommended

for

most

applications. For highest efficiency, the inductor

DC resistance should be less than 15mΩ. For

most designs, the inductance value can be

derived from the following equation.

OSC

L

IN

OUT

IN

OUT

f

I

V

)

V

V

(

V

L

×

Δ

×

−

×

=

Choose inductor current to be approximately

30% of the maximum load current, 5A. The

maximum inductor peak current is:

2

I

I

I

L

LOAD

)

MAX

(

L

Δ

+

=

Under light load conditions below 100mA, larger

inductance is recommended for improved efficiency.

Output Rectifier Diode

The output rectifier diode supplies the current to

the inductor when the high-side switch is off. To

reduce losses due to the diode forward voltage

and recovery times, use a Schottky diode.

Choose a diode whose maximum reverse voltage

rating is greater than the maximum input voltage,

and whose current rating is greater than the

maximum load current. Table 2 lists example

Schottky diodes and manufacturers.

Table 2—Diode Selection Guide

Diode

Voltage/Current

Rating

Manufacture

B530C

30V, 5A

Diodes Inc.

MBRD630CT

30V, 6A

On Semi

Selecting the Input Capacitor

The input capacitor (C1) reduces the surge

current drawn from the input and the switching

noise from the device. The input capacitor

impedance at the switching frequency should be

less than the input source impedance to prevent

high frequency switching current from passing to

the input. Ceramic capacitors with X5R or X7R

dielectrics are highly recommended because of

their low ESR and small temperature coefficients.

For 5A output applications, a 22µF capacitor is

sufficient.

Selecting the Output Capacitor

The output capacitor (C2) keeps output voltage

small and ensures regulation loop stability. The

output capacitor impedance should be low at the

switching frequency. Ceramic capacitors with

X5R or X7R dielectrics are recommended.