MICRF211 datasheet(14/18 Pages) MICREL

14 / 18 page

Micrel

MICRF211

March 2007

M9999-030107

(408) 944-0800

PCB Considerations and Layout

Figure 12 to 17 below show some of the printed circuit

layers for the QR211HE1 board. Use the Gerber files

provided (downloadable from Micrel Website) which

have the remaining layers needed to fabricate this

board. When copying or making your own boards,

make traces as short as possible. Long traces alter

the matching network and the values suggested are

no longer valid. Suggested Matching Values may vary

due to PCB variations. A PCB trace 100 mills (2.5mm)

long has about 1.1nH inductance. Optimization should

always be done with exhaustive range tests. Make

individual ground connections to the ground plane

with a Via for each ground connection. Do not share

Vias

with

ground

connections.

Each

ground

connection = 1 via or more vias. Ground plane must

be solid and possibly without interruptions. Avoid

ground plane on top next to the matching elements. It

normally adds additional stray capacitance which

changes the matching. Do not use phenolic material,

only FR4 or better materials. Phenolic material is

conductive above 200MHz. RF path should be as

straight as possible avoiding loops and unnecessary

turns. Separate ground and VDD lines from other

circuits (microcontroller, etc). Known sources of noise

should be laid out as far as possible from the RF

circuits. Avoid thick traces, the higher the frequency,

the thinner the trace should be in order to minimize

losses in the RF path.

Figure 12. QR211HE1 Top Layer.

Figure 13. QR211HE1 Bottom Layer, Mirror Image.

MICRF211 Datasheet(PDF) 14 Page - Micrel Semiconductor