Hi Everyone,
I am reviewing my application for safe operation at low voltage. It is on a MSP430F5438A.
I have the following configuration:
- SVS/SVM High and Low - disabled
- ADC12 measuring Vbatt using external resistor pair (fet switched) with Avcc as the reference
I want to make sure the voltage is sufficient to the msp430 for writing to the internal flash to avoid corruption.
How should I ensure that I only use the ADC12 when the voltage is greater than or equal to 2.2V as per the datasheet if I am using the ADC12 to measure the battery?
I have been looking at the SVS High to solve this problem - is that the right approach? I see I could pick the Reset Release to say 2.3V (typ - SVSMHRRL_3) to ensure when the msp430 wakes up from lpm the ADC12 reading can be trusted. In terms of the reset level, the highest 2.18V (typ) would still allow the ADC12 to operate at of specification (min 2.10V) - SVSHRVL_3.
In my application I think I have a way out of this, and this I choose not to stay awake for extended periods of time when the battery is less than 3V. This effectively means that I can rely on reset release. However, the device I am making can also be powered from a cable - and if the battery was flat (less than 2.2V) when the cable is removed, how could I determine whether I should run or not - reset and see if once again if Reset Release allows MSP430 to boot-up?
Writing this has helped me think about this - maybe the SVM High side flag would be set to indicate the voltage is lower than the reset release?
Hopefully this makes sense to someone who can help me straighten out my thinking.
Edit: If this thinking is looking okay, is SVSMHRRL_3 and SVSHRVL_3 valid - as I found my msp430 only worked with SVSHRVL_1... and also when the SVS holds the device in reset (above BOR) does it consume more current? I was seeing a 1mA.
Best Regards,James