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CC1101: Operation outside datasheet frequencies

Tim Kerby
Prodigy 10 points
Part Number: CC1101

Hi

I've noticed some devices operate this chip outside the officially supported datasheet frequencies. I'm presuming they have done extended testing and within the operating voltage/temperature they are confident of the performance.

From my experiments, the risk here is that the chip may fail to lock the pll although I have seen some concerns that the output amplifier may be damaged outside these ranges.

Could someone from TI perhaps comment on the risks of unofficial operating frequencies?

I'm interested in a few things

- What are the risks if operating outside datasheet bands - can it cause damage or is it pll lock issues, frequency drift etc?

- If the pll doesn't lock correctly, does the device still apply power to the antenna (e.g. risk of transmitting way off band)

- What are the risks of antenna mismatch? If the antenna doesn't present a normal 50 ohm load (i.e. poor SWR) can the output amplifier be damaged and if so, whats an acceptable mismatch?

Many thanks

  • 0
    Prodigy 10 points

    I should add too that this isn't for any production device - it's for an in-house development setup in an EMC chamber where we think we may need to send some signals on a wider range of frequencies, and we already have this transceiver on the board. We just don't want to break our existing boards!

  • 0
    TI__Mastermind 33190 points

    Hi Tim,

    The frequency range of the chip is always tested in the verification tests and there is always some design margin included before the VCO and/or PLL has problems operating for a specified frequency range. Working outside the frequency range can cause issues with the VCO and/or PLL and/or divider not operating correctly. If the VCO is operating outside it's standard frequency range, there are risks of unwanted emissions and no oscillation. The PLL can also fail to lock if operating outside it's standard frequency range and will still apply power to the antenna.

    Risks with antenna mismatch are increased harmonics, reduced output power and increased current consumption. Generally, the antenna mismatch can be large and the output stage will not be damaged when presented with a large mismatch for short periods of time. However, if the antenna mismatch is very poor for long periods of time, then this can effect the longevity of the chip especially if further stressed with maximum voltage and maximum temperature. Recommend to keep the VSWR better than 5:1 for worst case scenarios.

    Best regards,

       Richard