Freescale Semiconductor Demonstration Board for Freescale MC9S12XHY256 Microcontroller DEMO9S12XHY256 DEMO9S12XHY256 用户手册

Freescale Semiconductor

765

The PCB must be carefully laid out to ensure proper operation of the voltage regulator as well as of the
MCU itself. The following rules must be observed:

•

Every supply pair must be decoupled by a ceramic capacitor connected as near as possible to the
corresponding pins .

•

Central point of the ground star should be the VSS3 pin.

•

Use low ohmic low inductance connections between VSS1, VSS2 and VSS3.

•

VSSPLL must be directly connected to VSS3.

•

Keep traces of VSSPLL, EXTAL, and XTAL as short as possible and occupied board area for
C12,C11, and Q1 as small as possible.

•

Do not place other signals or supplies underneath area occupied by C12,C11, and Q1 and the
connection area to the MCU.

•

Central power input should be fed in at the VDDA/VSSA pins.

Example layouts are illustrated on the following pages.

C1

V

DDX1

 filter capacitor

X7R/tantalum

>=100 nF

C2

V

DDM1

 filter capacitor

X7R/tantalum

>=47 uF

C3

V

DDM2

 filter capacitor

X7R/tantalum

>=47 uF

C4

V

DDPLL

 filter capacitor

Ceramic X7R

220 nF

C5

V

LCD

 filter capacitor

Ceramic X7R

>=100 nF

C6

V

DDX2

 filter capacitor

X7R/tantalum

>=100 nF

C7

V

DDA

filter capacitor

Ceramic X7R

>=100 nF

C8

V

DDR

 filter capacitor

X7R/tantalum

>=100 nF

C9

V

DD

filter capacitor

Ceramic X7R

220 nF

C10

V

DDF

filter capacitor

Ceramic X7R

220 nF

C11

OSC load capacitor

From crystal manufacturer

C12

OSC load capacitor

Q1

Quartz

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