CC2480 datasheet(34/48 Pages) TI

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CC2480

10.11 System Considerations and Guidelines

10.11.1

SRD regulations

International regulations and national laws

regulate the use of radio receivers and

transmitters. SRDs (Short Range Devices) for

license free operation are allowed to operate

in the 2.4 GHz band worldwide. The most

important regulations are ETSI EN 300 328

and EN 300 440 (Europe), FCC CFR-47 part

15.247 and 15.249 (USA), and ARIB STD-T66

(Japan).

10.11.2

Frequency hopping and multi-channel systems

The 2.4 GHz band is shared by many systems

both

industrial,

office

and

home

environments.

CC2480 uses direct sequence

spread spectrum (DSSS) as defined by [1] to

spread the output power, thereby making the

communication link more robust even in a

noisy environment.

10.11.3

Crystal accuracy and drift

A crystal accuracy of ±40 ppm is required for

compliance with IEEE 802.15.4 [1]. This

accuracy

must

also

take

ageing

and

temperature drift into consideration.

A crystal with low temperature drift and low

aging

could

used

without

further

compensation. A trimmer capacitor in the

crystal oscillator circuit (in parallel with C191 in

Figure 5) could be used to set the initial

frequency accurately.

For non-IEEE 802.15.4 systems, the robust

demodulator in

CC2480 allows up to 140 ppm

total frequency offset between the transmitter

and receiver. This could e.g. relax the

accuracy requirement to 60 ppm for each of

the devices.

Optionally in a star network topology, the full-

function device (FFD) could be equipped with

a more accurate crystal thereby relaxing the

requirement on the reduced-function device

(RFD). This can make sense in systems where

the reduced-function devices ship in higher

volumes than the full-function devices.

10.11.4

Communication robustness

CC2480 provides very good adjacent, alternate

and co channel rejection, image frequency

suppression and blocking properties. The

CC2480 performance is significantly better than

the requirements imposed by [1]. These are

highly

important

parameters

for

reliable

operation in the 2.4 GHz band, since an

increasing number of devices/systems are

using this license free frequency band.

10.11.5

Communication security

The hardware encryption and authentication

operations

CC2480

enable

secure

communication, which is required for many

applications. Security operations require a lot

of data processing, which is costly in an 8-bit

microcontroller system. The hardware support

within

CC2480 enables a high level of security

with minimum CPU processing requirements.

10.11.6

Low cost systems

As the

CC2480 provides 250 kbps multi-

channel performance without any external

filters, a very low cost system can be made

(e.g.

two

layer

PCB

with

single-sided

component mounting).

A differential antenna will eliminate the need

for a balun, and the DC biasing can be

achieved in the antenna topology.

10.11.7

Battery operated systems

In low power applications, the

CC2480 should

be placed in the low-power modes PM2 or

PM3 when not active. Ultra low power

consumption may be achieved since the

voltage regulators are turned off.

CC2480 Data Sheet SWRS074

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