MC9S12KG128_10 Datasheet, PDF (601/606 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Appendix B Recommended PCB Layout
The PCB must be carefully laid out to ensure proper operation of the voltage regulator as well as of the
MCU itself{Statement}. 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 (C1 - C6).
• Central point of the ground star should be the VSSR pin.
• Use low ohmic low inductance connections between VSS1, VSS2 and VSSR.
• VSSPLL must be directly connected to VSSR.
• 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.
Component
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
R1
Q1
Table B-1. Recommended Components
Purpose
VDD1 filter cap
VDD2 filter cap (80
QFP only)
VDDA filter cap
VDDR filter cap
VDDPLL filter cap
VDDX filter cap
OSC load cap
OSC load cap
PLL loop filter cap
PLL loop filter cap
PLL loop filter res
Quartz
Type
ceramic X7R
ceramic X7R
ceramic X7R
X7R/tantalum
ceramic X7R
X7R/tantalum
Value
400nF
400nF
100nF
>=100nF
200nF
>=100nF
See PLL specification chapter
MC9S12KG128 Data Sheet, Rev. 1.16
Freescale Semiconductor
601