LPC540: Voltage at ADC input before VDD

[jana_beck]

Hi,
I have a design, where I am trying to measure voltages with a LPC54016.
One ADC input is a voltage, that will be on an ADC pin, before the MCU gets powered.

I have VCC_5V that gets converted into VCC_3V3 with a step down DCDC converter.
I have 5V going to an ADC input (with a voltage divider, so it is 2.25V at the pin).
That means, that the 2.25V will be on the ADC pin before 3.3V at the power supply pins.

Can this damage the MCU?

Thanks,
Jana

[Omar_Anguiano]

Hello Jana Beck

Due to the internal circuitry, it is not recommendable to apply voltage to the pins before powering the VDD, this may cause you trouble with the MCU.

I apologize for the inconvenience this is causing you, if you have more questions do not hesitate to ask me.

Best regards,

Omar