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TMS320F28375S: TMS320F28375S: VDD reset threshold

Thuc Nguyen Duy
Prodigy 20 points
Part Number: TMS320F28375S

Hi Ti E2E,

I am using a TMS320F28375S in my project. To supply VDD (1.2V) to MCU, I used a BUCK converter.

I encountered a problem as follow: When I tried to download firmware to flash of the MCU, the process was failed. It was due to a sudden current draw from MCU, which caused a voltage dip on the VDD pin of MCU. The MCU detected this undervoltage, and generates a reset event, which caused the failure in downloading firmware to flash.

I decided to supply 1.2V from a external power supply instead of the buck converter, and the download process was successful.

So, my next task will be to improve the dynamic response of the BUCK converter so that it response better to the sudden load increase.

I tried to find the reset threshold of the VDD undervoltage in the MCU's datasheet and manual, but I couldn't find that value.

So my question is: What is the threshold of VDD, at which the MCU will generate a reset signal?

I am looking forward to your answer.

Best Regards,

Nguyen Duy Thuc.

  • +1
    TI__Guru* 77460 points

    Nguyen,

    The threshold on this device is not tuned to be precise, but more of a stop gap in case of big droop in the core voltage, it is ~1.01V vs the 1.2V nominal(and 1.14V Vmin).  If you are seeing the XRSn get driven due to this, then as you stated you'll need to increase your decap or bulk up the DC/DC to handled the current need.

    You can see the estimate of current consumption during flash programming here in the DS.

    Best,
    Matthew

  • 0 in reply to MatthewPate
    Prodigy 20 points

    Hi Matthew,

    Thank you for your answer.

    The recommended operating condition of VCC, from 1.14V to 1.26V corresponds to a 5% undershoot (or overshoot). I think this is achievable when the compensator of my regulator is well tuned.

    Have a nice day!

    Best Regards,

    Nguyen Duy Thuc.