MP8768 – 8A, 28V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFET

MP8768 Rev. 1.0

www.MonolithicPower.com

11

12/12/2013

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Table 3—BOM of Reference Design

Qty

Ref

Value

Description

Package Manufacturer Part Number

2

C1A, C1B

4.7µF

Ceramic Cap, 50V, X7R

1210

Murata

GRM32ER71H475KA88L

2

C2A, C2B

47µF

Ceramic Cap, 10V, X5R

1210

Murata

GRM32ER61A476KE20L

2

C3, C4

1µF

Ceramic Cap, 16V, X7R

0603

Murata

GRM188R71C105KA12D

0

C5

NS

1

C6

82pF

Ceramic Cap, 50V, COG

0603

Murata

GRM1885C1H820JA01D

1

R1

31.6k

Film Res., 1%

0603

Yageo

RC0603FR-0731K6L

1

R2

10k

Film Res., 1%

0603

Yageo

RC0603FR-0710KL

2

R3, R5

100k

Film Res., 5%

0603

Any

0

R4, R6, R8

NS

1

R7

10

Film Res., 5%

0603

Any

1

L1

1.5uH

10mΩ DCR, 14A

SMD

Wurth

744311150

1

M1

MOSFET, N-CH, 30V,

11.5mΩ

SO8

Fairchild

FDS6670AS

1

U1

Step-Down Converter

QFN14

MPS

MP8768DL

Also PCB layout is very important to achieve

stable operation. Please follow these guidelines

and take Figure 5 and 6 for references.

1) Keep the path of switching current short and

minimize the loop area formed by Input cap,

high-side and low-side MOSFETs.

2) Keep the connection of low-side MOSFET

between SW pin and input power ground as

short and wide as possible.

3) Place

the

feedback

resistors

and

compensation components as close to the

chip as possible.

4) Route SW away from sensitive analog areas

such as FB.

5) Connect IN, SW, and especially GND

respectively to a large copper area to

improve chip thermal performance and long-

term reliability.

6) It is suggested to add snubber circuit across

so as to reduce SW spikes.

R1

GND

BST

SW

IN

PG

FB

VCC

2

14

13

12

11

10

9

8

1

2

3

4

5

6

7

IN

IN

SW

SW

BG

C1A

R5

R2

C4

R7

EN

8

76

5

4

3

2

1

SGND

PGND

C2A

R3

R4

C5

R9

C6

R6

R8

C3

M1

C1B

C2B

AAM

Top Layer