MC9S12DT256 Device User Guide — V03.07
83
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 (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, C11 and Q1 as small as possible.
•
Do not place other signals or supplies underneath area occupied by C7, C8, C10 and Q1 and the
connection area to the MCU.
•
Central power input should be fed in at the VDDA/VSSA pins.
Component
Purpose
Type
Value
C1
VDD1 filter cap
ceramic X7R
100 .. 220nF
C2
VDD2 filter cap
ceramic X7R
100 .. 220nF
C3
VDDA filter cap
ceramic X7R
100nF
C4
VDDR filter cap
X7R/tantalum
>=100nF
C5
VDDPLL filter cap
ceramic X7R
100nF
C6
VDDX filter cap
X7R/tantalum
>=100nF
C7
OSC load cap
C8
OSC load cap
C9 / C
S
PLL loop filter cap
See PLL specification chapter
C10 / C
P
PLL loop filter cap
C11 / C
DC
DC cutoff cap
Colpitts mode only, if recommended by
quartz manufacturer
R1 / R
PLL loop filter res
See PLL Specification chapter
R2 / R
B
Pierce mode only
R3 / R
S
Q1
Quartz
Содержание MC9S12A256
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