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Any way to save power on boot-up (e.g. lower clock frequency)?

Jeff Stringer
Intellectual 320 points

I'm using a CC430x613x device and it looks like the default boot-up clock is 1MHz.  Is there any way to have the default boot-up clock be lower to save power on boot-up?  Or are there any other techniques to minimize the power required for boot?  In my application I'm powering the CC430 with an energy harvester.  Even though the energy harvester can put out 3.3V, when it first is able to do that the energy stored in the system isn't enough for boot.  It can take a longer time for it to have enough energy to boot even though it can provide the 3.3V.  One approach is to have an external circuit monitor the energy and then when there is enough for boot, release the processor reset.  However, I'd like to avoid the extra circuit cost.

Thanks,
Jeff

  • 0
    Guru 227245 points

    Jeff Stringer said:
    Is there any way to have the default boot-up clock be lower to save power on boot-up?

    No. But the first action you can do is setting MCLK to REFO or VLO. And the same for SMCLK, which wil allow the DCO to go off.

    To delay the boot, you may add a large capacitor on RST, which will delay the startup. However, this will collide with the usage of SBW for debugging - you'll need to do 4-wire JTAG instead.

    Anyway, at startup the internal voltage regulator has to start and charge the 470nF capacitor for the core. Which will require some current anyway.

    I suggest using a larger storage capacitor in front of the regulator, and a monitor chip that enables the MSP only if the storage capacitor is sufficiently charged.

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