17

 2005 Semtech Corp.

www.semtech.com

SC1485

POWER MANAGEMENT

The layout can be considered in two parts, the control section referenced to VSSA1/2 and the power section.

Looking at the control section first, locate all components referenced to VSSA1/2 on the schematic and place

these components at the chip. Connect VSSA1 and VSSA2 using either a wide (>0.020”) trace. Very little current

flows in the chip ground therefore large areas of copper are not needed.

R8

10R

0402

0402

0402

0402

C15

56p

0402

0402

0603

0603

VOUT2

EN/PSV1

22

TON1

23

VOUT1

24

VCCA1

25

FB1

26

PGD1

27

VSSA1

28

PGND1

1

DL1

2

VDDP1

3

ILIM1

4

LX1

5

DH1

6

BST1

7

EN/PSV2

8

TON2

9

VOUT2

10

VCCA2

11

FB2

12

PGD2

13

VSSA2

14

PGND2

15

DL2

16

VDDP2

17

ILIM2

18

LX2

19

DH2

20

BST2

21

U1

SC1485

C9

1uF

R4

R3

VOUT

VBAT

C4

1nF

R1

PGOOD

5VSUS

C10

1uF

5VSUS

R2

10R

0402

0402

0402

0402

C7

0402

0402

0603

0603

VOUT1

VSSA2

VSSA1

C19

1uF

R9

20k0

R13

20k0

VOUT

C18

1nF

5VSUS

R7

1M

VBAT

PGOOD

C20

1uF

5VSUS

Figure 9: Components Connected to VSSA1 and VSSA2