MICRF507 datasheet(37/47 Pages) MICREL

37 / 47 page

Micrel, Inc.

MICRF507

October 2, 2013

Revision 2.2

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

can

found

the

Micrel

website

at:

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.

RF Traces

The ANT pin impedance is approximately 50

Ω. To

minimize reflection due to impedance mismatch, RF traces

should be a controlled impedance of 50

Ω 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.

MICRF507 Datasheet(PDF) 37 Page - Micrel Semiconductor

MICRF507 Datasheet(HTML) 37 Page - Micrel Semiconductor

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