MP4561 – 1.5A, 2MHz, 55V STEP-DOWN CONVERTER

MP4561 Rev. 1.0

www.MonolithicPower.com

11

11/5/2012

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Table 1—Inductor Selection Guide

Part Number

Inductance

(µH)

Max DCR

(Ω)

Current Rating

(A)

Dimensions

L x W x H (mm

Wurth Electronics

7447789004

4.7

0.033

2.9

7.3x7.3x3.2

744066100

10

0.035

3.6

10x10x3.8

744771115

15

0.025

3.75

12x12x6

744771122

22

0.031

3.37

12x12x6

TDK

RLF7030T-4R7

4.7

0.031

3.4

7.3x6.8x3.2

SLF10145T-100

10

0.0364

3

10.1x10.1x4.5

SLF12565T-150M4R2

15

0.0237

4.2

12.5x12.5x6.5

SLF12565T-220M3R5

22

0.0316

3.5

12.5x12.5x6.5

Toko

FDV0630-4R7M

4.7

0.049

3.3

7.7x7x3

919AS-100M

10

0.0265

4.3

10.3x10.3x4.5

919AS-160M

16

0.0492

3.3

10.3x10.3x4.5

919AS-220M

22

0.0776

3

10.3x10.3x4.5

Table 2—Diode Selection Guide

Diodes

Voltage/

Current

Rating

Manufacturer

B290-13-F

90V, 2A

Diodes Inc.

B380-13-F

80V, 3A

Diodes Inc.

CMSH2-100M

100V, 2A

Central Semi

CMSH3-100MA

100V, 3A

Central Semi

Input Capacitor

The input current to the step-down converter is

discontinuous, therefore a capacitor is required to

supply the AC current to the step-down converter

while maintaining the DC input voltage. Use low

ESR capacitors for the best performance.

Ceramic capacitors are preferred, but tantalum or

low-ESR electrolytic capacitors may also suffice.

For simplification, choose the input capacitor with

RMS current rating greater than half of the

maximum load current. The input capacitor (C1)

can be electrolytic, tantalum or ceramic.

When using electrolytic or tantalum capacitors, a

small, high quality ceramic capacitor, i.e. 0.1μF,

should be placed as close to the IC as possible.

When using ceramic capacitors, make sure that

they have enough capacitance to provide

sufficient charge to prevent excessive voltage

ripple at input. The input voltage ripple caused by

capacitance can be estimated by:

LOAD

OUT

OUT

IN

IN

SIN

IV

V

ΔV1

fC1

V

V

⎛⎞

=×

× −

⎜⎟

×

⎝⎠