TMS320F28377S: Power on Reset Sequence problem

Your subject line says "TMS320F28377S", but the body of the post says "TMS320F28388SPTPT". I presume the latter is correct.

I have sent you a friendship request. Once you accept my request, you will be able to send the schematics privately to me.

Please clarify what you mean by “the CPU doesn't work”. Are you able to connect to the device through CCS? If so, are you able to run a simple code from RAM? Exactly what is not working? If there is a way to drive the -XRS pin low after the supply rails have stabilized, can you please induce a "warm reset" and see if that fixes the issue? if not, the issue is unlikely to be related to power sequencing.

Violation of power sequencing is likely to induce long-term reliability issues. In general, it should not prevent the device from working.

I have received a tiny snippet of the schematic as a low-resolution image. If I zoom it, I am not able to discern anything, so what you have sent is not useful. To properly analyze the issue, I need the complete schematic as a PDF file, not as an image. If you don’t want to send the complete schematics, at the very least, I need to see every connection to the MCU. Without this, I will not be able to do any meaningful debug. 

Please answer all questions below accurately: 

1. Please clarify what you mean by “the CPU doesn't work”. Are you able to connect to the device through CCS?
2. If so, are you able to run a simple code from RAM? Exactly what is not working?
3. If there is a way to drive the -XRS pin low after the supply rails have stabilized, can you please induce a "warm reset" and see if that fixes the issue?
4. How is VREGENZ tied?
5. What is the total capacitance on VDD & VDDIO pins?
6. Why does the VDD looks very noisy?
7. Can you check the current drawn from VDD?

Hi,

I'm sorry for the confusion.

The CPU works fine. However customer is worried that it could be a problem because the customer's reset waveform is different from the datasheet.

I asked the customer for a schematic as a PDF files.

And I'm checking your questions. I will reply as soon as possible. 

Thanks,

SY Yoon said:

The CPU works fine.

This is contradictory to what you said in the first post: "the CPU doesn't work".  OK, so the device works fine but the customer is worried that the power-up waveform is not matching what is mandated in the datasheet? I presume that answers questions 1, 2, 3 & 7 in my last post. If you send the schematics, that would answer 4 & 5. 

That leaves us with only #6. Can you please send a better image that clearly shows the ripple on VDD?

On a different note, please refer to 6.12.1 Power Management Module (PMM) in page 72 of www.ti.com/lit/SPRSP61. Understand it is the datasheet for a different device. Nevertheless, much of that section is applicable to TMS320F2838x as well.