I am developing a blasting monitoring sensor for which I have chosen to use the STM32L496 as my main chip. The application requires sampling from an external ADC at about 12kHz. When the uC will be reading the samples, it will have to perform a comparison and then decide whether to perform a recording for an interval of about 30 seconds or just store the samples on the SRAM of the uC. The SRAM would only need about 2 seconds of recording and will be constantly overwritten, this is done to ensure to a 1 second pre-trigger recording. The idea is to have the uC in a low-power mode and then wake it up when the external ADC is ready to send the sample. The uC would then go in active mode, do its processing, and then go back to the low-power mode unless it needs to record.
My main concern in developing this sensor is to save as much power as possible and thus, here are a few questions I have:
- What is the best low-power mode to use for my application? My intuition tells me I should be targeting the one with the lowest wake-up time that can retain the SRAM, which seems to be the Stop0 mode. However, the current consumption is much lower in Stop1 (~4.6uA) than in Stop0 (100uA) while the wakeup time only increases from 0.7us to 4us (with code in SRAM). Perhaps this Stop1 mode is more suited for my application? While it wakes up, is the uC consuming current as if in run mode or is it slowly transitioning from the low-power mode current consumption to the active mode current consumption?
- Speaking of wake-up time, would using external oscillators help in any way to reduce it or to reduce power consumption in general? It appears from reading application notes that the only purpose of the HSE external oscillator is to increase the accuracy of the clock but I am not sure whether or not that would be useful in my application. As for the LSE, the AN4555 mentions it being low-power so is that recommended in such an application?
Thanks for the help.
Xavier Lajoumard de Bellabre