nRF52840 Power FAIL

[Oleg]

    Hi Engineers!
    We made our own ten (10) PCB's with nRF52840 MCU onboard fully according to "Circuit configuration no. 3":
    1. LDO only mode (VDDH connected to VDD  connected to +3.3v).
    2. EXTSUPPLY (UICR) bit = 0.
    
    all tens MCU's do not start.
    at all DECx pins ~6Mhz signal exist of ~2,8V amplitude (see pic)
    What wrong ?

osc_6M.JPG

[FormerMember]

Could you upload the schematic and layout?

[Oleg]

here are TOP PCB layer and SCHEMA.

PCB_BLE.JPG

[Oleg]

attached here

[Oleg]

Another problem, QIAA case is VERY expensive for our Fabric. if any schedule to use another one package in the future ? actualt case dont fit us anyway and should be changed.

[Oleg]

Problem Solved by soldering all N.C. capacitors (DEC2 and DEC5) to 104.