MFR4300_07 Datasheet, PDF (259/266 Pages) Freescale Semiconductor, Inc – FlexRay Communication Controllers

Printed Circuit Board Layout Recommendations
Appendix C
Printed Circuit Board Layout Recommendations
The PCB must be laid out carefully to ensure proper operation of the voltage regulator and the CC. 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 (Cd).
• The central point of the ground star should be the VSSR pin.
• Low-ohmic low-inductance connections should be used between VSSX and VSSR.
• VSSOSC must be directly connected to VSSR.
• Traces of VSSOSC, EXTAL and XTAL must be kept as short as possible. Occupied board area for
C1, C2, C3 and Q should be as small as possible.
• Other signals or supply lines should not be routed under the area occupied by C1, C2, C3, and Q
and the connection area of the CC.
• The central power input should be fed in at the VDDA/VSSA pins.
Figure C-1 shows a recommended PCB layout (64-pin LQFP) for standard Pierce oscillator mode, while
Table C-1 provides suggested values for the external components.
Table C-1. Suggested External Component Values
Component
C1
C2
C3
C4
Cd
Cload
R_B
R_S
Q
Purpose
OSC load cap
OSC load cap
VDDOSC filter cap
VDDA filter cap
VDDR, VDDX filter cap
VDD2_5 filter cap
OSC resistance
OSC resistance
Quartz
Type
ceramic X7R
ceramic X7R
ceramic X7R
ceramic X7R
ceramic X7R/tantalum
ceramic X7R
NDK NX8045GA
Value
2pF
2pF
100– 220nF
100– 220nF
100– 220nF
100– 220nF
1 MΩ
0 Ω (i.e. short-circuit)
40 MHz
MFR4300 Data Sheet, Rev. 3
Freescale Semiconductor
259