micrf507ymltr Micrel Semiconductor, micrf507ymltr Datasheet - Page 37

• Manufacturer Part Number: micrf507ymltr
• Description: 470mhz To 510mhz Low-power Fsk Transceiver With +10dbm Power Amplifier
• Manufacturer: Micrel Semiconductor

Layout Considerations
To ensure the best RF performance, a carefully planned
layout is essential. Grounding, RF path geometry, supply
routing, and layer definition all play a role in an optimal
design. These are discussed below, and a recommended
layout
(www.micrel.com).
Layer Definition
A typical MICRF507 PCB design consists of four layers,
with the following stack-up:
Layer1 – Component and RF routing
Layer2 – Ground
Layer3 – VDD Routing
Layer 4 – Non-RF Routing
While not the only acceptable definition, this example
provides a good foundation for the general techniques
discussed below.
Grounding
Design the layout to provide the shortest possible return
path for signals and noise sources. Place ground vias
close to all critical items such as ground pins on the RF IC,
decoupling capacitors, and matching components.
March 2010
Micrel, Inc.
can
be
found
on
the
Micrel
website
37
RF Traces
The ANT pin impedance is approximately 50Ω. To
minimize reflection due to impedance mismatch, RF traces
should be a controlled impedance of 50Ω as well. Refer to
the Micrel Development Board layout, or a transmission
line impedance calculator to verify a specific geometry’s
characteristic impedance.
Supply Routing
The radio system is sensitive to supply noise and signals
coupled from one section to another. Routing the supply
lines on an internal layer (below the ground layer)
separates them from potential noise sources such as the
reference oscillator, PA, charge pump, etc. Route supplies
separately and place bypass capacitors as close as
possible to the associated pin.
PLL Loop Filter
Place loop filter components close to each other and near
pins 27 and 29. Connection of the loop filter to VDD should
occur very close to VCOVDD, pin 31. Avoid routing
potentially noisy busses or traces near the loop filter.
M9999-032210-B
MICRF507