SC173AEVB datasheet(19/26 Pages) SEMTECH

19 / 26 page

Layout Guideline

Since the SC173A has integrated switches, special con-

sideration should be given to board layout. Let us use the

schematic shown above as an example. The board level

layout is illustrated in the following four layers.

As shown on the top layer layout, U1 is the switching

regulator SC173A. C1 and C11 serve as the decoupling

capacitor for the buck converter power train. C11, with a

value between 1nF and 10nF, is the high frequency filter-

ing capacitor. It is recommended to put C1 and C11 as

close as possible to the SC173A to get the best decou-

pling performance, with C11 closest. C1, with a value of

10uF, should be placed no more than 3mm away from

the VIN pin. L1 is the output filtering inductor. C2, C3 and

C4 are the output filtering capacitors. C5 is the boostrap

capacitor. Pin 10 (VDD) is the input bias power for the

internal circuits. It is recommended to get the power

from VIN through an RC filtering network consisted of R1,

C6 and C10. The value of R1 can be between 3.01W and

10W and the capacitance of C10 should be above 1mF.

C6, with a value of 1nF, is the high frequency filtering ca-

pacitor. The locations of C6 and C10 should be as close as

possible to pins 9 and 10, with C6 closest, to get the best

possible filtering result. R2 is the on-time programming

resistor. R2 should be located as close as possible to pin

8 and it should return to analog ground. Pull EN high

(above 1V) or permit it to float to enable the part with

automatic power save enabled. Connect EN to AGND to

disable the switching regulator.

Since there are two integrated MOSFETs inside the

SC173A that will dissipate a lot of power, to help spread

the heat out of the IC more efficiently, there is a thermal

pad underneath the SC173A serving as a heat sink. To

enlarge the heat sinking area, a large copper plane un-

der the thermal pad as shown on the top layer is recom-

mended.

On inner layer 2, a large analog ground plane (AGND) on

the right hand side is connected to the thermal pad un-

derneath the SC173A using vias. Thus the heat generated

inside the SC173A can be spread through the vias to the

BST

VIN

PGND

TON

AGND

VDD

PGOOD

Enable

VIN+

VIN-

VO+

VO-

SC173A

C10

C11

Schematic for layout illustration

SC173A

SC173AEVB датащи(PDF) 19 Page - Semtech Corporation

SC173AEVB датащи(HTML) 19 Page - Semtech Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

датащи скачать

ссылки URL