AN2826 Freescale Semiconductor / Motorola, AN2826 Datasheet - Page 15

• Manufacturer Part Number: AN2826
• Description: DDR-SDRAM Layout Considerations for MCF547x/8x Processors
• Manufacturer: Freescale Semiconductor / Motorola

MCF547x/8x Validation Board DDR Layout
Figure 11. MCF547x/8x Validation Board Power Plane
Figure 11
shows one of the power planes (+3.3V) on the validation PCB. The other power planes (+1.5V
& +2.5V) are not shown in this document because they are almost identical to the one shown above. Most
importantly the plot above is a negative; white represents flood filled with copper. The holes shown in the
copper are to accommodate through board components and thermal relief. The most critical thing to notice
on this plot are the “boxes” around the footprint for the MPU and the DDR SDRAM DIMM. These areas
of copper are created to force the supply to the MPU and DDR SDRAM DIMM through the
de-coupling/bypass capacitors, thus increasing their effectiveness. If the reader refers back to the first
diagram, the top silkscreen for the PCB
(Figure
6), they will see that the decoupling capacitors for both
the MPU and the DDR SDRAM are positioned along the edges of these boxes.
DDR-SDRAM Layout Considerations for MCF547x/8x Processors, Rev. 1
Freescale Semiconductor
15