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CC430 - Do we need VCore Level 2 for Radio?

Other Parts Discussed in Thread: CC430F6125, CC430F6135, CC430F5135, RF430F5978, CC430F5137, CC430F5133, CC430F6126, CC430F6127, CC430F6137, CC1101

Hi all,

In CC430 RF Examples, there are these lines:

// Increase PMMCOREV level to 2 for proper radio operation
SetVCore(2);

I tried using level 2 as the example suggests. The transmitter worked fine with a new battery but it went into BOR state (kept resetting) very early when the battery got just a little bit low.

I tried level 0 (just use the default setting) and my transmitter worked fine in a wide voltage range (could go as low as 1.9).

The transmitter was running at 5.01MHz, the battery was a coin cell CR2477 (3V).

So my question is:  Do we really need to set VCore to level 2 for proper radio operation? Why isn't this mentioned anywhere in the user guide?

Someone has posted a similar question but had no final answer yet.

Thank you.

  • If the transmitter works down to 1.9V, it doesn't mean it works within the specification. Maybe output power is significantly less, maybe frequency stability is worse, maybe some devices fail earlier, some later.
    PMMCOREV_2 will reset the device if DVCC falls below 2.2V and allow up to 16MHz CPU speed. PMMCOREV_= will allow operation down to 1.8V and limit speed to 8MHz. However, proper transmitter operation is not guaranteed.
    The datasheet specifies required supply voltage to be 2.0 to 3.6V, which would only exclude PMMCOREV=0, but in the next line it demands PMMCOREV=2 or 3.
    So the information is there and it is where it belongs. The users guide is not the place for device-specific voltages or levels. This kind of information belongs to the device-specific datasheet (as maybe a different CC430 could well be designed for operation on PMMCOREV=0).
    And it is there, right at the start of the RF module specifications.
  • Thank you. I see it now. I did not look close enough. It is mentioned in CC430F6137, CC430F6135, CC430F6127, CC430F6126, CC430F6125, CC430F5137, CC430F5135, CC430F5133 datasheet and in RF430F5978 datasheet.

    We have different products that use CC430, one of them use 3V coin cell battery as I mentioned. It is quite impossible for us to use VCore Level 2. Reason:
    During transmission, voltage drops 0.3V. So the minimum battery voltage has to be 2.5 to use VCore Level 2, to be safe it should be 2.6. The coin cell battery will go from 3V to 2.6V really quickly especially the thin ones. So customers will have to replace their batteries too frequently. Do you have any recommendation on how to solve this? Older versions of our products use MSP430 with CC1101, we are able to set low battery threshold at 2.2V. If we use VCore Level 2 on our new products, the battery threshold has to be 2.6 or higher (battery is measured during transmissions).
  • You can use a buck/boost regulator to output 2.6V from any battery voltage, from 3.0V down to ~0.8V. This drains a bit more current for the regulator, but allows to squeeze much more energy out of the battery, extending effective use time. Using some more µF buffer capacitance relaxes the peek current form battery during transmission.

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