PL904XXX Datasheet, PDF (8/15 Pages) Micrel Semiconductor – a small form-factor, high performance, programmable device

Micrel, Inc.
Power Supply Filtering Recommendations
Preferred filter, using Micrel’s MIC94300 or MIC94310 Ripple Blocker™:
Alternative, traditional filter, using a ferrite bead:
PL904xxx
VDDO and VDD pins can be connected directly to the VDD power plane. For VDDA and VDDI it is recommended to use a
power supply filter as described above.
Application Information
Power Supply Decoupling
Place the smallest value decoupling capacitor (4.7nF
above) between the VDD and VSS pins, as close as
possible to those pins and on the same side of the PCB as
the IC. The shorter the physical path from VDD to the
capacitor and back from the capacitor to VSS, the more
effective the decoupling. Use one 4.7nF capacitor for each
VDD pin on the PL904xxx.
The impedance value of the ferrite bead (FB) needs to be
between 240Ω and 600Ω with a saturation current
≥150mA.
VDDO pins connect directly to the VDD plane. All VDD
pins on the PL904xxx connect to VDD after the power
supply filter.
A Ripple Blocker has advantages over using a ferrite bead.
A Ripple Blocker filters much lower frequencies than a
ferrite bead, at least two decades lower. Most ferrite beads
cause peaking in the noise filter frequency response, so
some noise frequencies are actually made worse. The
Ripple Blocker is designed to not have any noise peaking.
Output Traces
Design the traces for the output signals according to the
output logic requirements. If LVCMOS is unterminated,
add a 30Ω resistor in series with the output, as close as
possible to the output pin, and start a 50Ω trace on the
other side of the resistor.
For differential traces, you can either use a differential
design or two separate 50Ω traces. For EMI reasons, it is
better to use a differential design.
LVDS can be AC-coupled or DC-coupled to its termination.
September 11, 2015
8
Revision 1.0
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