13

© 2003 Semtech Corp.

www.semtech.com

POWER MANAGEMENT

SC2616

Applications Information (Cont.)

Guidelines for Layout of DDR Supply Using SC2616 DDR

Controllers on Typical Motherboards

Signals of arbitrary importance (signals that can be routed

last, such as SLP_S3, SLP_S5, 5VCC) have been omitted

for simplicity.

Parameters of importance in the Layout of the DDR power

section are as follows (in order of importance):

1. The VTT decoupling cap,C15, must be placed less than

0.25 inch from Controller.

2. The power rail decoupling cap,C4, must be placed

less than 0.25 inch from Q2 drain.

3. The decoupling caps for 5VSBY AND 12Vcc,C13 and

C8, must be placed very close to the controller(0.25inch

or less)

4. The VDDQ sense lines must be routed from a distant

load point (do not connect to the inductor output at the

VDDQ plane near the controller/FETS. Place the voltage

divider at the load point and route the divider center and

the sense ground close together as a differential pair.

Connect the AGND and the sensed ground and LGND at

the chip.

5. The VTTSNS must be connected to a distant load

point.

6. Adequate copper area must be allocated to both

VDDQ and VTT. The copper coverage must be uniform, i.

e. it provides low resistance to all areas around the

DIMMs. VDDQIN traces (and vias if used to carry current)

must be adequate for 2.0Amps.

7. Make the phase node area, which connects the

Inductor, Top FET and the Bottom FET, as small as

possible to prevent EMI, and ringing. Avoid making this

Evaluation Board Schematic

C13

1uF

0

R6

2R2

C12

R8

1k

5VSBY

5VCC

12VCC

Q1

0

U1

SC2616

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

FB

VTTSNS

LGND

5VSBY

VTT

VTT

VDDQSTBY

VDDQIN

5VCC

SLP_S5

SLP_S3

AGND

PGND

BG

TG

12VCC

COMP

SS/EN

0

C16

1n

C11

FB

R3

2R2

VTT

L1 3uH

Q2

5VCC

0

VDDQ

C9

SLP_S3

R9

2R2

R4

2R2

C14

R13

2.2R

0

C2

0

C17

1uF

C7

D1

0

FB

C10

C5

5VCC

VDDQ

0

0

C8

1uF

R2

43K

R1

2R2

C6

15n

C4

0

0

Q3

C1

C15

4.7uF

R5

1k

C3

R7

2R2

C18

1uF

12VCC

SLP_S5

0

C19