According to Errata #13 (ENGcm12387) in MCIMX27CE.pdf (rev 0.7), iMX27 has the limitation condition when MPLL Is restarted.
Does anyone know that this issue gives any impacts to Bootstrap in iMX27 Rev2.2 ?
Any information or actual experience would be helpful, thanks in advance.
Yes, it does. Are you experiencing problems booting in 2.2? Did your system boot fine with 2.1 and older? You can determine if the problem is this errata by changing the QVDD and MPLLVDD default voltage. I'll be happy to help if you want me to, I'd just need some more details about your application.
Thank you for your prompt reply.
As you told, Bootstrap in the production board works successfully with QVDD=1.2V. However, QVDD=1.5V case is wrong.
MPLLVDD voltage is fixed at the range of 1.5 to 1.6V. (This voltage can't be changed due to PCB circuit.)
If you need more information, pls let me know.
I'm still not sure the relationship between QVDD voltage range and Errata.
Could you explain in detail ?
The thing is, in 2.2, we had to reduce the timing between MPLL restart and CSRC register clear to fix an old issue. This fix introduced errata ENGcm12387. Now, if you lower QVDD or MPLLVDD, the internal timings of the MX27 that are related to this errata are relaxed and the errata is fixed. From your description, seems like this is actually the cause of your issue. I'd suggest:
- Go back to 2.1, which is still being produced.
- Or lower QVDD just to be able to enter bootstrap mode and program your boards. And when the boards are programmed, go back to a proper QVDD level, boot normally and continue using your application with a QVDD value that's within the spec. Please note that 1.2V is out of spec, so we recommend to use it only to program the board, not for the final application.
Thank you for your kind assistance.
I understand your explanation and the reason why Bootstrap did work in the case of lower QVDD.
One thing is still opened for me.
"Please note that 1.2V is out of spec", I have a question for this statement.
According to MCIMX27EC.pdf ( datasheet ), Table 7 details Core Supply Voltage for QVDD.
In case of @266MHz, QVDD should be in the range from 1.2V to 1.52V. Does it mean that
QVDD accepts 1.2V ? Otherwise, MPLLVDD should be in the range from 1.35V to 1.6V.
For MPLLVDD, 1.2V level is out of spec as you told.
Let me confirm my understanding.
Thanks in advance.
You're right, I was confusing the voltages. MPLLVDD is the one that doesn't allow 1.2V. QVDD is fine at 1.2V.
Sorry about the confusion.