IMXRT1062 POR_B fails and stays pulled low

[odd_bikes]

Hi,

We have this incredibly odd situation whereby the whole POR_B line gets pulled low. There's no real pattern, happens in maybe 0.5% of power-up cases for our product. The effect we notice is as shows in the screenshot attached, essentially even though the supervisor chip should pull the line high and allow the MCU to start, the line stays low. The real oddity is that, if we leave the product powered for anywhere between 5-60 minutes, it will recover and resume functioning as usual. 

There is one thing in the design which strays from the official EVK schematic: the pull-up for POR_B is to 3V3, while VDD_SNVS_IN is connected to 3V3 through a diode. But we don't use SNVS mode.

[Omar_Anguiano]

Could you share some scopes of the POR_b along with the power sources? Ideally, the external IC should control the POR_b status at power-up so if it stays stuck the issue may be on the IC.

Best regards,
Omar