Custom Board not Powering Up

[jcc273]

Hello,

We have created a custom board using the OSD3358-SM and it is not powering up.  We followed the information in the app notes for the power so I am not sure what the problem is.  I have attached the page showing the wiring for the part.  We are powering through USB only, there is no short and the whole board is drawing > 50mA from the 5V supply right now.  When I apply power I can see it start to power up momentarily but then it shuts back down.  SYS_RTC_1P8V goes to 1.8V shortly as does PMIC_LDO_PGOOD, PMIC_PWR_EN, and for a briefer time PMIC_WAKEUP and SYS_VDD1_1P8V but then they all drop back low.  I have tried using a button across R12 to hold the PMIC_PM_IN low to see if that would power it up but it was also no good.  Any suggestions where to go from here????

Thanks,

Jarrod

Attachments:

1. 

   OSD335xSchematic.png
   

[jcc273]

Figured it out.  So i followed the power up sequence chart in order and found that no rails after the SYS_VDD_1P8V came up.  I then examined other parts on that rail and found one that was in backwards and causing that rail to drag down which must have stopped and shut-off the PMIC.  So all is well now : )

[Greg Sheridan]

Great.  Glad you got it working!  Let us know if you need anything else.

[Author]

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