I'm working on a microcontroller design where the mcu is placed in hibernation mode, and can only be awoken by a pulse(high-low-high) signal on the reset pin. (active low)
As a wake-up source i'm using an accelerometer or an external RTC.
The idea is to have the accelerometer trigger an interrupt, that drives an interrupt pin low. The same goes for the RTC. It will pull an interrupt pin to logic low signal. However, this won't wake the mcu from hibernation mode. I need to use this sleep-mode to save as much power as possible.
I'm wondering how I can create a toggle signal from the interrupt-pin signal form the wakeup sources. The toggle must only happen once, since its the reset-pin of the mcu. Is there any kind of latches of logic circuits/components that create this kind of signal?
Edit: Pulse of (High-low-high) signal, not toggle(low-high-low)
I'm using an Energy Micro Gecko (EMF32G890F128) with a Cortex-M3 core.
My energy budget is low, my design should stay as low as <100µA active, and currently with RTC and accelerometer this is achieved.
Edit2: The interrupt signals from both accelerometer and RTC stays low until reset by mcu. Usually this is done by reading a register in the peripheral unit. And for this to happen the mcu must be awake.
Best Answer
A monostable multivibrator circuit can provide the pulse (not toggle) that the question seems to describe, and can be triggered as per requirement.
Monostables can be made in many ways, such as using bipolar junction transistors as per the schematic above, or using the venerable 555 timer as shown below.
If you must use a 555, consider the ultra low power CSS555C timer, which has a supply current of 5 to 10 µA. Even this may be well over the power budget for the application.
Specifically, note the "C" at the end of the part number: This indicates an internal capacitor integrated on the chip, thus reducing current consumption further.