Before talking about the microcontroller, we need to know why we need power sequencing. Power sequencing ensures that different voltage rails (core, I/O, analog, memory, etc.) are powered up and down in a safe order. Incorrect sequencing can cause:
-
Latch-up or internal short circuits
- High inrush currents or over stress on I/O pins
- Improper initialization of peripherals or flash
- Unpredictable boot behavior
Yes, Microcontroller do have sequencing requirement. Sequencing depends on the architecture, voltage domains, and peripherals involved.
- It starts with a RESET signal, the RESET signal should not be released until the power supply reaches a desired level. Below is a RESET release requirement from RA4M1 datasheet. RESET is an active low signal.
- The sequencing must be in this order:
- Core voltage must be powered first
- I/O and Analog voltages to be applied after core voltage. Ensure that Core is powered while the I/O is applied else this might cause damage to the core
- Analog Reference voltage
- External peripheral connected to the microcontroller to be powered up only after above sequence.
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