CC1000-RTR2 datasheet(37/55 Pages) TI

37 / 55 page

CC1000

SWRS048A

Page 37 of 55

26. System Considerations and Guidelines

26.1 SRD regulations

International regulations and national laws

regulate the use of radio receivers and

transmitters. SRDs (Short Range Devices)

for licence free operation are allowed to

operate in the 433 and 868-870 MHz

bands in most European countries. In the

United States such devices operate in the

260–470 and 902-928 MHz bands.

CC1000

is designed to meet the requirements for

operation in all these bands. A summary

of the most important aspects of these

regulations can be found in Application

Note AN001 SRD regulations for licence

free transceiver operation, available from

Chipcon’s web site.

26.2 Low cost systems

In systems where low cost is of great

importance the

CC1000 is the ideal choice.

Very few external components keep the

total cost at a minimum. The oscillator

crystal can then be a low cost crystal with

50 ppm frequency tolerance.

26.3 Battery operated systems

In low power applications the power down

mode should be used when not being

active. Depending on the start-up time

requirement, the oscillator core can be

powered during power down. See page 28

for information on how effective power

management can be implemented.

26.4 Crystal drift compensation

A unique feature in

CC1000 is the very fine

frequency resolution of 250 Hz. This can

used

the

temperature

compensation

the

crystal

the

temperature drift curve is known and a

temperature sensor is included in the

system. Even initial adjustment can be

done using the frequency programmability.

This eliminates the need for an expensive

TCXO and trimming in some applications.

In less demanding applications a crystal

with low temperature drift and low ageing

could

used

without

further

compensation. A trimmer capacitor in the

crystal oscillator circuit (in parallel with

C171) could be used to set the initial

frequency accurately. The fine frequency

step programming cannot be used in RX

mode if optimised frequency settings are

required (see page 24).

26.5 High reliability systems

Using a SAW filter as a preselector will

improve the communication reliability in

harsh

environments

reducing

the

probability

blocking.

The

receiver

sensitivity and the output power will be

reduced due to the filter insertion loss. By

inserting the filter in the RX path only,

together with an external RX/TX switch,

only the receiver sensitivity is reduced,

and

output

power

remained.

The

CHP_OUT (LOCK) pin can be configured

to control an external LNA, RX/TX switch

or power amplifier. This is controlled by

LOCK_SELECT in the LOCK register.

26.6 Frequency hopping spread

spectrum systems

Due to the very fast frequency shift

properties of the PLL, the

CC1000 is also

suitable for frequency hopping systems.

Hop rates of 1-100 hops/s are usually

used depending on the bit rate and the

amount of data to be sent during each

transmission. The two frequency registers

(FREQ_A and FREQ_B) are designed

such that the ‘next’ frequency can be

programmed while the ‘present’ frequency

is used. The switching between the two

frequencies is done through the MAIN

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