CC1100-RTY1 datasheet(58/100 Pages) TI1

58 / 100 page

CC1100

SWRS038D

Page 58 of 92

32.2 Frequency

Hopping

and

Multi-

Channel Systems

The 433 MHz, 868 MHz, or 915 MHz bands

are shared by many systems both in industrial,

office, and home environments. It is therefore

recommended to use frequency hopping

spread spectrum (FHSS) or a multi-channel

protocol because the frequency diversity

makes the system more robust with respect to

interference from other systems operating in

the same frequency band. FHSS also combats

multipath fading.

CC1100 is highly suited for FHSS or multi-

channel systems due to its agile frequency

synthesizer

and

effective

communication

interface. Using the packet handling support

and data buffering is also beneficial in such

systems as these features will significantly

offload the host controller.

Charge pump current, VCO current, and VCO

capacitance array calibration data is required

for

each

frequency

when

implementing

frequency hopping for

CC1100. There are 3

ways of obtaining the calibration data from the

chip:

1) Frequency hopping with calibration for each

hop. The PLL calibration time is approximately

720 µs. The blanking interval between each

frequency hop is then approximately 810 us.

2) Fast frequency hopping without calibration

for each hop can be done by calibrating each

frequency at startup and saving the resulting

FSCAL3

, FSCAL2, and FSCAL1 register values

in MCU memory. Between each frequency

hop, the calibration process can then be

replaced by writing the FSCAL3, FSCAL2and

FSCAL1

next RF frequency. The PLL turn on time is

approximately

90 µs. The blanking interval

between

each

frequency

hop

then

approximately 90 us. The VCO current

calibration result available in FSCAL2 is not

dependent on the RF frequency. Neither is the

charge

pump

current

calibration

result

available in FSCAL3. The same value can

therefore be used for all frequencies.

3) Run calibration on a single frequency at

startup. Next write 0 to FSCAL3[5:4] to

disable the charge pump calibration. After

writing to FSCAL3[5:4] strobe SRX (or STX)

with MCSM0.FS_AUTOCAL=1 for each new

frequency hop. That is, VCO current and VCO

capacitance calibration is done but not charge

pump current calibration. When charge pump

current calibration is disabled the calibration

time is reduced from approximately 720 µs to

approximately 150 µs. The blanking interval

between

each

frequency

hop

then

approximately 240 us.

There is a trade off between blanking time and

memory space needed for storing calibration

data in non-volatile memory. Solution 2) above

gives the shortest blanking interval, but

requires more memory space to store

calibration

values.

Solution

gives

approximately 570 µs smaller blanking interval

than solution 1).

Note that the recommended settings for

TEST0.VCO_SEL_CAL_EN

will change with

frequency. This means that one should always

use SmartRF

® Studio [7] to get the correct

settings for a specific frequency before doing a

calibration, regardless of which calibration

method is being used.

It must be noted that the TESTn registers (n =

0, 1, or 2) content is not retained in SLEEP

state, and thus it is necessary to re-write these

registers when returning from the SLEEP

state.

32.3 Wideband

Modulation

not

Using

Spread Spectrum

Digital modulation systems under FFC part

15.247 includes 2-FSK and GFSK modulation.

A maximum peak output power of 1W (+30

dBm) is allowed if the 6 dB bandwidth of the

modulated signal exceeds 500 kHz. In

addition, the peak power spectral density

conducted to the antenna shall not be greater

than +8 dBm in any 3 kHz band.

Operating at high data rates and frequency

separation, the

CC1100 is suited for systems

targeting compliance with digital modulation

system as defined by FFC part 15.247. An

external power amplifier is needed to increase

the output above +10 dBm.

32.4 Data Burst Transmissions

The high maximum data rate of

CC1100 opens

up for burst transmissions. A low average data

rate link (e.g. 10 kBaud), can be realized using

a higher over-the-air data rate. Buffering the

data and transmitting in bursts at high data

rate (e.g. 500 kBaud) will reduce the time in

active mode, and hence also reduce the

average current consumption significantly.

Reducing the time in active mode will reduce

the likelihood of collisions with other systems

in the same frequency range.

CC1100-RTY1 Datasheet(PDF) 58 Page - Texas Instruments

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