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TMS320F28066: MCU gets hanged during unstable powering on

Wayne Huang
Genius 16635 points
Part Number: TMS320F28066


Dear Champs,

I am asking this for our customer.

They used to use F28066 well.

But recently, they modified some design with larger load so that 3.3V powering-on (ramping) became unstable, which made F28066 hang even the supply became 3.3V. 

It seems the watchdog code could not work either when F28066 hanged.

Please see the below oscilloscope snapshots during power-on.

CH1: Power supply input from PV ; CH2: F28066 Pin11(XRS) ; CH3: 3.3V

Questions:

1. As there are POR and BOR, why does F28066 hangs after the 3.3V is finally stable?

2. Do you think it is possible to solve this issue by F28066 FW alone without modifying their HW?

Wayne Huang

  • +1
    TI__Guru* 95315 points
    Wayne Huang said:
    they modified some design with larger load so that 3.3V powering-on (ramping) became unstable

    Modifications in the power stage (controlled by the MCU) should not impact the input supply ramp for the MCU. This indicates a potential design anomaly.

    Wayne Huang said:
    1. As there are POR and BOR, why does F28066 hangs after the 3.3V is finally stable?

    POR has nothing to do with the issue you are describing. I doubt if this has anything to do with BOR either based on the second figure where -XRS appears to be asserted repeatedly even when 3.3v is stable.

    Wayne Huang said:
    2. Do you think it is possible to solve this issue by F28066 FW alone without modifying their HW?

    I don't have enough information about the problem but, in general, H/W issues related to power-supply ramping are not fixable in firmware.