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 2006 Semtech Corp.

www.semtech.com

SC486

POWER MANAGEMENT

Layout Guidelines (Cont.)

In Figure 8, all components referenced to VSSA have been placed and have been connected using a 0.020” trace.

Decoupling capacitor C12 is as close as possible to VCCA and VSSA and the VDDP decoupling capacitor C18 is as

close as possible to VDDP and PGND1. The feedback components R5, R8 and C1 along with the VDDQ sense

components, R4 and C2 are also located at the chip and the feedback trace from the VDDQ output should route

from the top of the output capacitors (C13 and C14) in a quiet layer back to these components. In Figure 8, the

VDDQ feedback trace would connect to the red trace.

+

C14

220u/15m

+

C13

220u/15m

VDDQ

R4 10R

C2

1u

R5 4k64

R8

23k2

C1

no-pop

PGND1

18

REF

8

EN/PSV

1

TON

2

VDDQS

3

VCCA

5

FB

6

PGD

7

VSSA

4

PGND2

17

DL

19

VDDP

20

ILIM

21

LX

22

DH

23

BST

24

VTTEN

11

VTT

15

PGND2

16

VTTIN

12

VTTIN

13

VTT

14

VTTS

10

COMP

9

PAD

U1

SC486

VDDQ FEEDBACK

Figure 9: VDDQ Feedback and Sense Components and Feedback Trace