IMX280 power on reset threshold voltage

[Cookie456]

Hello

I have a question with IMX280DVM4B power on reset voltage.

Application note "IMX28CEC" said  "Because the i.MX28 is a PMU and an SoC, power-on reset is generated internally and there is no timing requirement on external pins." 

But it didn't mention the specific power on reset threshold voltage.

Now we plan to add external reset circuit to control "RESETN" pin by monitoring VDD5V power source. so I would like to know the exact power on reset threshold value for i.MX280 internal design. Probably we are able to refer to the threshold voltage.

[Rita_Wang]

Recommend you to use our reference design.

[Cookie456]

There is a manual reset circuit in our current design. It is similar with NXP reference design. but it is not able to solve the problem we meet now. when VDD_5V falls below 4.75V due to power interuption, power supply recovers before VDD_5V falls to zero,but the system can't restart automatically. so we plan to add an external reset circuit by monitoring VDD_5V in order to realize system restart automatically.
So could you please check power on reset threshold voltage internally? or do you hanve any other recommendations to solve this problem?