TMS570LC4357: NERROR during bootup

Ryan Wang

Part Number: TMS570LC4357

Experts,

During TMS570LC4357 bootup, occasionally , NERROR pin change from low->high->low->high, totally in 15us. Vcore voltage is 0.9V by then. After bootup, everything looks fine. Is it normal? and why?

thanks

over 5 years ago

0 QJ Wang over 5 years ago

TI__Guru**** 197336 points

Hi Ryan,

The nERROR has default pull (pull-down) enabled while nPORRST is low, and the pull is disabled immediately after nPORRST goes High.

If the nERROR pin has a external pull-up resistor, the nERROR pin is LOW until nPORRST is released.

low->high->low->high --> is not normal.

0 Ryan Wang over 5 years ago in reply to QJ Wang

TI__Expert 7495 points

QJ,

thanks for your feedback.

So where I should check for this abnormal phenomenon?

0 Sunil Oak over 5 years ago in reply to Ryan Wang

TI__Mastermind 49120 points

Please ensure nPORRST is driven low until the I/O and core supplies are within the recommended operating range for at least the minimum duration specified in the datasheet.

0 QJ Wang over 5 years ago in reply to Sunil Oak

TI__Guru**** 197336 points

This is the waveform of nERROR and nPORRST. Both pin have an external pull-up resistor.

As sunil suggested, please ask your customer to checking the timing nPORRST, and VCC/VCCIO.

0 Ryan Wang over 5 years ago in reply to QJ Wang

TI__Expert 7495 points

QJ, Sunil,

great thanks for suggestion. I will check

0 user4919786 over 5 years ago in reply to Sunil Oak

Prodigy 120 points

Thanks sunil，

I have confirmed nPORRST is driven high before core supply within the recommended operating range，this would lead to any other problems？

0 Sunil Oak over 5 years ago in reply to user4919786

TI__Mastermind 49120 points

Yes, this will cause issues. Please make sure that datasheet requirements for nPORRST timings are followed strictly.

Regards, Sunil

0 Ryan Wang over 5 years ago in reply to Sunil Oak

TI__Expert 7495 points

Sunil,

some questions:

1. what will happen if nPORRST is driven high before core supply within the recommended operating range.

2. NERROR abnormal phenomenon is caused by item 1, right?

3. In picture 6.1 of datahsheet, it is said nPORRST need to drive low 2us after 1.2V voltage drop to below 1.14V. However, Chapter 6.3.2 said there is no power down sequence requirement. Could you comment on this? what will happen if power down sequence doesn't be met?

thanks

0 Sunil Oak over 5 years ago in reply to Ryan Wang

TI__Mastermind 49120 points

Ryan,

We cannot predict the behavior of the part if the core supply is not within the recommended operating range.

Picture 6.1 says that nPORRST must be driven 2us before core supply drops below 1.14V. Most system designers meet this requirement by tuning the core supply up (e.g. 1.26V nominal instead of 1.2V), and setting the low-threshold higher than 1.14V.

The section 6.3.2 says that there is no strict sequencing requirement between the core and I/O supplies. This still requires the nPORRST timing requirements to be strictly met.

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TMS570LC4357: NERROR during bootup