MSP430F5659: LPM3, DCO stability and temperature

Willem Buitendyk

Part Number: MSP430F5659
Other Parts Discussed in Thread: MSP430F1612

The Family users guide suggests setting the DCO to its lowest value while in extended periods of low power mode?

How long is extended? Hours, Days, Weeks, Months? Is it more a question of temperature changes? In an older project (MSP430F1612), an engineer we used set our processor to wake up every 15 seconds to re-calibrate the DCO and then return to LPM3. Now that I'm designing this new project I wondering what the best, recommended course of action is? Ideally, I'd like to have as low power as possible and possibly for up to 8 months at a stretch through -10C to 30C temperatures

over 4 years ago

0 Allen Gao over 4 years ago

TI__Expert 7080 points

The period depends on the the range of temperature change and your expectation of your project. You can use energy trace to test the average power consumption of your project and evaluate the working time using battery.

0 Willem Buitendyk over 4 years ago

Prodigy 140 points

Ok I'm going to narrow my question down a little bit. I'm running at 20Mhz and have my initialization using DCORSEL_4 (first range where 20Mhz is apparent). If I set the DCO to its lowest value (DCORSEL_0) prior to entering extended low power mode do I need to change the DCO value again after coming out of LPM3? Do I need to set it back to DCORSEL_4 after exiting LPM3?

0 Willem Buitendyk over 4 years ago in reply to Willem Buitendyk

Prodigy 140 points

So it does appear I need to change it back to DCORSEL_4 in order to get back to 20MHz. Is that all there is to it in order to avoid an instability issue due to temperature?

+1 Allen Gao over 4 years ago in reply to Willem Buitendyk

TI__Expert 7080 points

Yes, you need to reset the DCORESL to the correct range. And check the FLLN and FLLD is the correct setting.

0 Willem Buitendyk over 4 years ago in reply to Allen Gao

Prodigy 140 points

Thank you. I also need to clear the DCO fault bit as well as that gets triggered when I lower the DCO before sleep.

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MSP430F5659: LPM3, DCO stability and temperature