CC1000
SWRS048A Page 38 of 55
27. PCB Layout Recommendations
Chipcon provide reference layouts that
should be followed in order to achieve the
best performance. The Chipcon reference
design (CC1000PP and
CC1000uCSP_EM) can be downloaded
from the Chipcon website.
A two layer PCB is highly recommended.
The bottom layer of the PCB should be the
“ground-layer”.
The top layer should be used for signal
routing, and the open areas should be
filled with etallization connected to
ground using several vias.
The ground pins should be connected to
ground as close as possible to the
package pin using individual vias. The de-
coupling capacitors should also be placed
as close as possible to the supply pins
and connected to the ground plane by
separate vias.
The external components should be as
small as possible and surface mount
devices are required. The VCO inductor
must be placed as close as possible to the
chip and symmetrical with respect to the
input pins.
Precaution should be used when placing
the microcontroller in order to avoid
interference with the RF circuitry.
In certain applications where the ground
plane for the digital circuitry is expected to
be noisy, the ground plane may be split in
an analogue and a digital part. All AGND
pins and AVDD de-coupling capacitors
should be connected to the analogue
ground plane. All DGND pins and DVDD
de-coupling capacitors should be
connected to the digital ground. The
connection between the two ground
planes should be implemented as a star
connection with the power supply ground.
A development kit with a fully assembled
PCB is available, and can be used as a
guideline for layout.
28. Antenna Considerations
CC1000
can be used together with various
types of antennas. The most common
antennas for short range communication
are monopole, helical and loop antennas.
Monopole antennas are resonant
antennas with a length corresponding to
one quarter of the electrical wavelength
(λ/4). They are very easy to design and
can be implemented simply as a “piece of
wire” or even integrated into the PCB.
Non-resonant monopole antennas shorter
than λ/4 can also be used, but at the
expense of range. In size and cost critical
applications such an antenna may very
well be integrated into the PCB.
Helical antennas can be thought of as a
combination of a monopole and a loop
antenna. They are a good compromise in
size critical applications. But helical
antennas tend to be more difficult to
optimise than the simple monopole.
Loop antennas are easy to integrate into
the PCB, but are less effective due to
difficult impedance matching because of
their very low radiation resistance.
For low power applications the λ/4-
monopole antenna is recommended giving
the best range and because of its
simplicity.
The length of the λ/4-monopole antenna is
given by:
L = 7125 / f
where f is in MHz, giving the length in cm.
An antenna for 869 MHz should be 8.2
cm, and 16.4 cm for 434 MHz.
The antenna should be connected as
close as possible to the IC. If the antenna
is located away from the input pin the
antenna should be matched to the feeding
transmission line (50 Ω).
For a more thorough primer on antennas,
please refer to Application Note AN003
SRD Antennas available from Chipcon’s
web site.
