mc9s12uf32 Freescale Semiconductor, Inc, mc9s12uf32 Datasheet - Page 96

• Manufacturer Part Number: mc9s12uf32
• Description: System Chip Guide V01.05
• Manufacturer: Freescale Semiconductor, Inc

System on a Chip Guide — 9S12UF32DGV1/D V01.05
22.2 PCB Design Recommendation
The PCB must be carefully laid out to ensure proper operations of the voltage regulator as well as the MCU
itself. The following rules must be observed:
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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 VSSR pin.
Use low ohmic, low inductance connections between VSSR, VSSX, VSS3X, VSSA and VSSA1.
Keep traces of VSSA, EXTAL and XTAL as short as possible and occupied board area for C7, C8
and X1 as small as possible.
Do not place other signals or supplies underneath area occupied by C7, C8 and X1, and the
connection area to the MCU.
Central power input should be fed in at the VDDR/VSSR pins.
Table 22-1 Recommended decoupling capacitor choice
Component
R21
R22
Q1
C1
C2
C3
C4
C5
C6
R1
R2
R3
R4
C7
C8
R5
X1
NMOS transistor
decoupling cap
decoupling cap
decoupling cap
decoupling cap
decoupling cap
decoupling cap
RREF resistor
OSC load cap
OSC load cap
DMH resistor
DMF resistor
DMF resistor
OSC resistor
RPU resistor
DPF resistor
Purpose
Quartz
choice of C6 cap depends on the
See Voltage Regulator Appendix
impedance matching resistors
X7R/tantalum
X7R/tantalum
ceramic X7R
ceramic X7R
ceramic X7R
See crystal manufacturer’s
depend on board design
type of NMOS transistor
Type
recommendations
>=100nF
>=100nF
100nF
100nF
100nF
Value
Freescale Semiconductor