nRF54 Debug Interface During Abrupt Power‑Off

[joey]

HI

    My gateway adopts CAT1 and nRF54, which communicate with each other via UART. The UART signals from the CAT1 module are 3.3 V level translated by the TXB0108 and fed directly to the nRF54.
    The 3.3 V supply for nRF54 and the 3.3 V supply for TXB0108 come from two separate LDOs, while both LDOs are fed from the same upstream DCDC converter.
    When the main power supply is abruptly removed, the nRF54 debug‑download interface gets locked up. Its internal storage becomes inaccessible and firmware fails to execute. This state persists even after a hardware reset.

    The only recovery method is a full mass erase followed by re‑flashing the firmware. This failure occurs almost every time the power cord is unplugged.
    I have added series diodes on the UART signal pins to mitigate back‑injection current, which improves the situation, yet the fault still occurs with low probability.

   

   This fault can be reproduced not only on my custom PCB design, but also with the off‑the‑shelf nRF54 demo board.  How should I resolve this issue?

Thanks!

[Simonr]

Hi

How is the power supply removed here on the nRF54L DK exactly? I think maybe the device could be trigging on the tamper controller, but I need more information on what you're doing exactly. You can check the TAMPC register if it's been triggered.

Can you potentially tell me how I can reproduce this on an nRF54L15 DK on my end so I can read out some registers to see what happens here?

Best regards,

Simon

[joey]

On the development board, the UART pins are directly connected to a module equipped with the TXB0108. The TXB0108 module is powered by a separate 3.3 V supply, while the development board itself draws power from its on‑board USB port. During normal operation, if the USB cable of the dev‑board is unplugged abruptly while the TXB0108 module remains powered, the system crashes with high probability.