[bpiquette]

The mid level voltage on SYS_VDD3_3P3V are puzzling.

[bpiquette]

This is what I see on my PCBA.
It appears that the TL5209 output, SYS_VDD1_3P3V comes up before LDO4 (SYS_VDD3_3P3V)

Attachments:

1. 

   SYS_VDD1_3P3V_timing-scaled.jpg
   

[bpiquette]

Example of good power on sequence

Attachments:

1. 

   good_boot-OSD335x-1-scaled.jpg
   

[bpiquette]

Unfortunately we did not add a test point to the SYS_VOUT node so I don’t have access to it.
I see SYS_RTC_1P8V come up as expected even in this failure mode.

We have discovered that when the PCBAs don’t boot, we see some excessive ripple on SYS_VDD1_3P3V (TL5209 output).
See attachments for comparison of good and bad power on.

• This reply was modified 2 years, 8 months ago by bpiquette.

Attachments:

1. 

   bad_boot-OSD335x-scaled.jpg
   

[bpiquette]

I suppose we would see that SYS_VOUT would not be as expected even if we have applied the VIN_AC?

[bpiquette]

Unfortunately, we did not include test points on this USB inputs pins, so probing will be hard.

Do you know of any other evidence to look for that would suggest that this is what is happening with our problem boards?

Apparently we have 3+ PCBAs that exhibit this problem fairly regularly (like 1 in 10 power cycles) but our customer has seen it on more of the devices that are in the field though less regularly.

[bpiquette]

Did you ever find a root cause for this issue?

[bpiquette]

We’ve had success with the same approach!

Thanks so much for blazing the trail EricT!

 

[bpiquette]

Neeraj, What is the recommended process for getting the eeprom programmed?

[bpiquette]

Any suggestions on the best method to program the EEPROM? We are seeing a very similar issue.

When we compare the SDcard commands on our board to those of the RED Dev board, we see a a pretty different looking trace.

The SD CLK is running at ~120kHz on our board, compared to 400kHz on RED is a clear example of the differences.

Can a non-programmed EEPROM cause these differences?

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