How to read datasheets
What is the main reason a datasheet for an IC with two supplies—1.0 V for the core and 3.3 V for I/O—specifies a power-up sequence?
- ABecause the power-up order determines the upper limit of the maximum operating frequency at which the product can run stably
- BBecause the wrong order can cause unintended internal current, leading to latch-up, damage or malfunction
- CBecause the order affects only power consumption at startup and has no effect on function or reliability
Show answer and explanation
Answer: B. Because the wrong order can cause unintended internal current, leading to latch-up, damage or malfunction
In an IC with multiple supplies, when only one supply is on, unexpected current can flow between supplies or through protection diodes on I/O pins. This can cause latch-up, device damage or malfunction due to undefined internal states. Datasheets give conditions such as "apply the core supply first and remove supplies in reverse order" or "keep the voltage difference between supplies below a certain value." On actual boards, the sequence is created using regulator enable pins and power-good signals.