OSD3358-512M-ICB hung up during power-up

[Sktz]

Have a very intermittent issue where the OSD3358-512M-ICB SIP gets hung up during power-up.
Device seems to not complete power-up cycle and begin operation.

Have not been able to recreate but receiving reports from offsite firmware developers working on the hardware.
Power is applied, device is hung for a period of time (10-20 seconds or so) and then completes power cycle and begins operation.
A quick power down/up cycle does not solve problem.

Key consideration – the OSD3358-512M-ICB is powered by an isolated DC/DC converter, +5V output, that has a unique power-up waveform.
See attached image, BLUE is isolated +5V in to OSD3358 at pins C18-C20, YELLOW is SYS_VOUT at pins F14-15/G15-15.

Could the rise/fall of the +5V in to OSD3358 during the initial 400mS be the cause?
Is the internal OSD3358 power monitoring reacting to this and causing the delay?

Thanks.

Attachments:

1. 

   5V_ISO_In_SYS_5V_Out.bmp
   

[Neeraj Dantu]

Sktz,

It seems like +5V input to OSD3358 experiences a glitch during power up. For the 5V power input(AC) there are 2 main requirements:
1. Rise time is < 50ms 2. Inrush is ~1500mA The scope shot indicates that the PMIC detects first power up and begins the internal power on sequence by switching SYS_VOUT ON. Then, +5V experiences a glitch resulting in a shutdown of the PMIC. It seems that +5V input does not go all the way down to 0V. In the scope shot, it only goes to ~2.7V. This is below the UVLO(default is set to 3.3V for the PMIC). So, PMIC is able to detect the next positive edge of the +5V signal for Auto turn-on. The suspicion is that in some cases, the +5V input does not go all the way down below UVLO voltage resulting in a lockup condition. Please take a look at https://www.ti.com/lit/an/slva901/slva901.pdf for more information on this type of brownout.

I think this glitch will need to be addressed in order to get reliable boot. Please also take a look at Sheet 1 of the SM-RED schematics: https://octavosystems.com/docs/osd3358-sm-red-schematics-pdf/ for a good power monitoring circuit that implements a solution to address brownout of the power input by adding a voltage monitor and switch.

Best,
Neeraj

[Sktz]

Thank you for your prompt response.
Just seeing this now as email notification didn’t work.
Will review.

[Author]

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