STM32H743 Failure behavior with external core SMPS
Greetings,
right know we are evaluating some strategies to reduces overall power consumption of our product, including two STM32H743 microcontrollers.
Due some other design restrictions the following options are not feasible:
- Switch to a low power µC
- Use the internal low power functions to reduce overall consumption
Basically it boils down to reduce the core voltage: Right know we simply provide 3,3V and the internal regulator feeds the core. With a Clock frequency of 400 MHz it runs at 1,2V resulting in 63% wasted energy from the regulator.
The reference manual mentions the possibility to feed the Core-Voltage from an external source with better efficiency ratio and we'd like to try this.
The design is part of a safety critical system and it is of paramount importance to have a defined output stage on one of our interfaces in case one mcu is defect.
Questions:
- Can you verify that when providing external core voltage of 1,2V the output voltages on all interfaces (GPIO, UART, SPI) are still the same 3,3V, stated that the controllers VDD pins are connected to the 3,3V rail?
- Can you explain what happens to the controller when the externally provided core power supply rises from 1,2V to a maximum of 3,3V? Is there some internal overvoltage protection that cuts the core and puts the µC in reset-state? Are the GPIO-output pins still in a defined state?
Greetings from Germany
Simon