i.MX 8M Incorrect PCIE Supply Configuration

[territao]

The PCIE_VPH power supply is selectable in software between 1.8V and 3.3V. When the PCIE_VPH supply is configured to operate at 3.3V, the 1.8V internal regulator (disabled by default) must be enabled to prevent overstress conditions on the PCIe PHY. If the 1.8V internal regulator is left disabled when the PCIE_VPH supply is configured to operate at 3.3V, it could potentially impact the product lifetime of the device. Here is the link to this patch:

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/i-MX-8M-Dual-8M-QuadLite-8M-Quad-Incorre...

I am trying to understand the impact of the statement below taken from the link you provided.

"If the 1.8V internal regulator is left disabled when the PCIE_VPH supply is configured to operate at 3.3V, it could potentially impact the product lifetime of the device."

For example, if I operate the i.MX8M 24 hours a day for 2 years how much has the product lifetime been affected? -50%, -75%, -100%?

 Also, because the regulator is initially bypassed (default) there is always some time during the boot cycle where the circuitry downstream of the regulator is being stressed until software enables the regulator. How significant is this sequence of events to the product lifetime? Assume 4 power cycles per day.

In addition to my questions in the previous post, we have found in one case when enabling the 1.8VDC internal regulator caused the PCIe PHY to stop working. Are there any side effects to enabling the regulator after the device has been stressed for a long period of time (regulator off and 3.3VDC applied to VPH)?

[jimmychan]

>> How significant is this sequence of events to the product lifetime? Assume 4 power cycles per day.

So far, i.MX Expert only provides solution and patches, and there is no data to quantify the problem you mentioned.

>> Are there any side effects to enabling the regulator after the device has been stressed for a long period of time (regulator off and 3.3VDC applied to VPH)?

As experts say, this will affect the life of the CPU.

[territao]

Thank you for the feedback, here are some new findings:

1. 1 unit with regulator off and 3.3VDC applied to VPH for about two years, PCIe link failed on this unit after the 1.8V applied to VPH, and PCIe link back to work after we apply 3.3V to VPH on this unit.

2. 3 units with regulator off and 3.3VDC applied to VPH for about 1.5 years, PCIe link failed on these units. We thought these 3 units were permanently broken, but after we applied 1.8V to VPH on these units, the PCIe link back to work.

We cannot explain these two findings, and we are unable to determine whether to apply the 1.8V patch to our shipping products or not, could you help to have the i.MX Expert have a look at this issue?

[jimmychan]

I got the reply from the expert:

The PCIE_VPH power supply is selectable in software between 1.8V and 3.3V. When the PCIE_VPH supply is configured to operate at 3.3V, the 1.8V internal regulator (disabled by default) must be enabled to prevent overstress conditions on the PCIe PHY.

If the 1.8V internal regulator is left disabled when the PCIE_VPH supply is configured to operate at 3.3V, it could potentially impact the product lifetime of the device.

For case 1, they are in normal situation.

For case 2, please check if 3.3 to 1.8 regulator works normally after patches applied.