converter circuit, output ripple voltage is determined

by inductor value, switching frequency, output

capacitor value and ESR. The output ripple is

determined by:

)

C

F

8

1

ESR

(

I

V

OUT

OSC

COUT

L

OUT















For a fixed output voltage, the output ripple is highest

input voltage. Two 22μF ceramic capacitors are

recommended value in typical application.

Inductor Selection

For high efficiencies, the inductor should have a low

DC resistance to minimize conduction losses.

Especially at high-switching frequencies, the core

material has a higher impact on efficiency. When

using small chip inductor, the efficiency is reduced

mainly due to higher inductor core losses. This needs

to be considered when selecting the appropriate

inductor. The inductor value determines the inductor

ripple current. The larger the inductor value, the

smaller the inductor ripple current and the lower the

conduction losses of the converter. Conversely, larger

inductor values cause a slower load transient response.

A reasonable starting point for setting ripple current,

ΔL, is 40% of maximum output current. The

recommended inductor value can be calculated as

below:

L

SW

MAX

,

IN

OUT

OUT

I

F

V

/

V

1

V

L











L

MAX

,

OUT

MAX

,

L

I

2

/

1

I

I









To avoid the saturation of the inductor, the

inductor should be rated at least for the

maximum output current of the converter plus the

inductor ripple current.

Layout Consideration

The layout design of

HM3412 regulator is relatively simple. For the best efficiency and minimum noise problems, we

1) Multi-layer board is suggested for HM3412 output current application. It is desirable to maximize the PCB copper area

connecting to GND pin to achieve the best thermal and noise performance. Reasonable vias are suggested to be placed

around GND pins to enhance the soldering quality and thermal performance.

3) The PCB copper area associated with SW pin must be minimized to avoid the potential noise problem.

layout to avoid the noise problem.

6V 6.0A 1.2MHz Synchronous Step-Down Regulator