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CC430F5137: CC430 Frequency Drift over Temperature

Colton Parks
Prodigy 20 points
Part Number: CC430F5137

We are running a CC430 at 433MHz with a CW test. Changing the temperature from 25C to 85C we see large deviations in frequency, around a few hundred kHz. Based on oscillator tolerances and stability, our tolerance should only be 36kHz. Doing a hard reset on the unit fixes the problem and the frequency tracks exactly where it's supposed to be. The same happens when moving from 85C to 25C. The ramp rate of the change is 3C/min and the RH is set to 35%. 

I would be interested to know what the CC430 or C1101 does under the hood for frequency calibration and how vulnerable it is to temperature changes when running a CW test. 

  • 0
    Guru 46710 points

    CC430 is packet radio, CW test across temperature range is meaningless. What it does under the hood - written in the user manual. Calibrate regularly is mentioned all over the document. Few excerpts:

    25.3.3.7.2 Active Modes The radio has two active modes: receive and transmit. These modes are activated directly by the CPU by using the SRX and STX command strobes. The frequency synthesizer must be calibrated regularly. There is one manual calibration option (using the SCAL strobe), and three automatic calibration options, controlled by the MCSM0.FS_AUTOCAL setting: • Calibrate when going from IDLE to either RX or TX (or FSTXON) • Calibrate when going from either RX or TX to IDLE automatically • Calibrate every fourth time when going from either RX or TX to IDLE automatically

    25.3.3.10.1 VCO and PLL Self-Calibration The VCO characteristics vary with temperature and supply voltage changes, as well as the desired operating frequency. To ensure reliable operation, the radio includes a frequency synthesizer selfcalibration circuitry. This calibration should be done regularly, and must be performed after turning on power and before using a new frequency (or channel).

    [edit] CC430 is cc-series radio with MCU in single package, so good idea is to ask radio-related questions in radio-related forum:

    https://e2e.ti.com/support/wireless_connectivity/proprietary_sub_1_ghz_simpliciti/

  • 0 in reply to Ilmars
    Prodigy 20 points

    Thank you! That answers my question perfectly!

    [also an edit] I thought it was originally the sub 1GHz forum, but if I input the part number and select the issue, it limits the forums to a subset of the original that doesn't include the sub 1GHz forum :(

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