MP2374 Rev. 1.0

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6

1/23/2014

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The input capacitor value should be greater

than 10μF. The capacitor can be electrolytic,

tantalum or ceramic. However, since it absorbs

the input switching current it requires an

adequate ripple current rating. Its RMS current

rating should be greater than approximately 1/2

of the DC load current.

For insuring stable operation C1 should be

placed as close to the IC as possible.

Alternately, a smaller high quality ceramic

0.1μF capacitor may be placed closer to the IC

and a larger capacitor placed farther away. If

using this technique, it is recommended that the

larger capacitor be a tantalum or electrolytic

type. All ceramic capacitors should be placed

close to the MP2374.

Output Capacitor (C5)

The output capacitor is required to maintain the

DC output voltage. Low ESR capacitors are

preferred to keep the output voltage ripple low.

The characteristics of the output capacitor also

affect the stability of the regulation control

system. Ceramic, tantalum or low ESR

electrolytic capacitors are recommended. In the

case of ceramic capacitors, the impedance at

the switching frequency is dominated by the

capacitance, and so the output voltage ripple is

mostly independent of the ESR. The output

voltage ripple is estimated to be:

2

SW

LC

IN

RIPPLE

f

f

V

4

.

1

V

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

×

×

≅

switching frequency.

In the case of tantalum or low-ESR electrolytic

capacitors, the ESR dominates the impedance

at the switching frequency, and so the output

ripple is calculated as:

ESR

RIPPLE

R

I

V

×

Δ

≅

output capacitors.

Output Rectifier Diode (D1)

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 rectifier.

Table 2 lists manufacturer’s websites.

Table 2—Schottky Diode Manufacturers

#

Vendor

Web Site

1

Diodes, Inc.

www.diodes.com

2

Fairchild Semiconductor

www.fairchildsemi.com

3

General Semiconductor

www.gensemi.com

4

International Rectifier

www.irf.com

5

On Semiconductor

www.onsemi.com

6

Pan Jit International

www.panjit.com.tw

Choose a rectifier whose maximum reverse

voltage rating is greater than the maximum

input voltage, and whose current rating is

greater than the maximum load current.