mc9s12xs128 Freescale Semiconductor, Inc, mc9s12xs128 Datasheet - Page 708

• Manufacturer Part Number: mc9s12xs128
• Description: Hcs12 Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

PCB Layout Guidelines
Appendix C
PCB Layout Guidelines
C.1
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:
Example layouts are illustrated on the following pages.
708
•
•
•
•
•
•
•
Component
C10
C11
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 C7,
C8, and Q1 as small as possible.
Do not place other signals or supplies underneath area occupied by C7, C8, and Q1 and the
connection area to the MCU.
Central power input should be fed in at the VDDA/VSSA pins.
Q1
C1
C2
C3
C4
C5
C6
C7
C8
C9
General
Table C-1. Recommended Decoupling Capacitor Choice
S12XS Family Reference Manual, Rev. 1.10
V
V
V
V
V
V
OSC load capacitor
OSC load capacitor
DDPLL
V
DDX2
DDX1
DDA1
DDR
DDF
DD
filter capacitor
Purpose
filter capacitor
filter capacitor
filter capacitor
filter capacitor
filter capacitor
Quartz
filter capacitor
N/A
N/A
X7R/tantalum
X7R/tantalum
X7R/tantalum
Ceramic X7R
Ceramic X7R
Ceramic X7R
Ceramic X7R
From crystal manufacturer
Type
—
—
—
Freescale Semiconductor
>=100 nF
>=100 nF
>=100 nF
>=100 nF
220 nF
220 nF
220 nF
Value
—
—
—