Analog Devices ADSP-BF506F Hardware Reference Manual page 1201

Connect the power plane to the power supply pins directly with minimum
trace length. A ground plane should be located near the component side of
the board to reduce the distance that ground current must travel through
vias. The ground planes must not be densely perforated with vias or traces
as their effectiveness is reduced.
is the highest frequency and requires special attention. Two things
VDDINT
help power filtering above 100 MHz. First, capacitors should be physically
small to reduce the inductance. Surface mount capacitors of size 0402 give
better results than larger sizes. Secondly, lower values of capacitance will
raise the resonant frequency of the LC circuit. While a cluster of 0.1
acceptable below 50 MHz, a mix of 0.1
pF is preferred in the 500 MHz range.
CASE 1:
BYPASS CAPACITORS ON NON-
COMPONENT (BOTTOM) SIDE OF
BOARD, BENEATH PACKAGE
Figure 25-1. Bypass Capacitor Placement
ADSP-BF50x Blackfin Processor Hardware Reference

F, 0.01
a
B
ADSP-BF50x
CASE 2:
BYPASS CAPACITORS ON
COMPONENT (TOP) SIDE OF
BOARD, AROUND PACKAGE
System Design
 
F, 0.001 F and even 100

F is
25-7