MCIMX8M-EVK - Hardware Design Understanding

[Haider_Ali]

Hello,

I was going through the schematic / hardware design of MCIMX8M-EVK (Evaluation Kit for the i.MX 8M Applications Processor) as a reference to make our custom board.

While reviewing power section, I came across following which is bugging me:

As I understood, the board is designed to be powered from 5V-20V, (12V adapter or USB PD ranging from 5V to 20V).

Now from the schematic, page 10, section "PMIC", the regulator "MP8759GD" with reference number "U701" is converting / stepping down the input voltage (net name "VSYS") to 3.3V output.

As per the datasheet of "MP8759GD" the voltage on EN pin cannot exceed 4.5V (Absolute rating) but from the schematic what I see is when the "VSYS" will be 20V the voltage on EN pin will be 5.7V which exceeds the 4.5V absolute rating. (Snaps below from the schematic of Eval board & datasheet of regulator). (I have also measured the voltage on EN pin and when input is 20V the voltage on EN pin is 5.4V approx..)

My question is if my understanding is correct or not and what can be the solution to this if I want to keep the input voltage range (VSYS) to be same as 5V to 20V range?

links to resources:
EVAL Board: https://www.nxp.com/design/design-center/development-boards-and-designs/i-mx-evaluation-and-developm...

Datasheet of "MP8759GD":https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datash...

[AldoG · Accepted solution]

Hello,

This is indeed correct, since the MP8759GD have an internal PD(600K) on EN pin, so if you apply simple math you'll see that at 20V the EN pin goes beyond the maximum allowed.

For this kind of approach I would suggest to take a look to either i.MX8MM or i.MX8MN base board schematic, it has the same IC and it has the correct resistor configuration that allows to use 20V as VSYS.

Best regards/Saludos,
Aldo.