Analog Devices ADSP-BF59x Blackfin, Hardware Reference Manual, Page: 705 / 772

ADSP-BF59x Blackfin Processor Hardware Reference 17-5
System Design
inside the package footprint of the processor (underneath it, on the bot-
tom of the board), not outside the footprint. A surface-mount capacitor is
recommended because of its lower series inductance.
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.
VDDINT
is the highest frequency and requires special attention. Two things
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
μ
F is
acceptable below 50 MHz, a mix of 0.1
μ
F, 0.01
μ
F, 0.001
μ
F and even
100 pF is preferred in the 500 MHz range.
Note that the instantaneous voltage on both internal and external power
pins must at all times be within the recommended operating conditions as
specified in the product data sheet. Local “bulk capacitance” (many micro-
farads) is also necessary. Although all capacitors should be kept close to
the power consuming device, small capacitance values should be the clos-
est and larger values may be placed further from the chip.