MICRF218 datasheet(19/23 Pages) MICREL

19 / 23 page

Micrel

MICRF218

November 2011

M9999-111111

(408) 944-0800

PCB Considerations and Layout

Figures 14 to 17 show top, bottom and silkscreen

layers of printed circuit board for the QR218HE1

board.

Gerber

files

are

provided

and

are

downloadable from Micrel Website: www.micrel.com,

to fabricate this board. Keep traces as short as

possible. Long traces will alter the matching network,

and the values suggested will not be 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. Use 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 14. QR218HE1 Top Layer.

Figure15. QR218HE1 Bottom Layer, Mirror Image.

MICRF218 Datasheet(PDF) 19 Page - Micrel Semiconductor