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TMS320F280025: Low temperature power on abnormal

Emma Wang
Expert 5290 points
Part Number: TMS320F280025


Hi expert,

I have a customer which is make the new project on F280025.

Recently , they are doing on high / low temperature test.

and they found at specific condition,

which temperature is -30 and VAC =165V, the 3.3V voltage will meet a drop, but did not have reset.

The temperature is -30 and VAC =220 or 265V, this phenomenon will not happen.

here is the two waveform and power train, the 12V is for another part and you can neglect it.

did you share some potential reason for this ?

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/171/low_5F00_temp_5F00_power_5F00_on.7z

BR

Emma

  • 0
    TI__Genius 15385 points

    Hi Emma,

    Give us couple of days to review the data that you send, one of our expert will respond to you in next day or two with more details.

    Best Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    TI__Mastermind 45606 points

    Hi Emma,

    I see in the waveforms provided that it's just the 3.3V rail experiencing the drop, 5V rail looks to ramp normally. What other circuitry (if any) is connected to the 3.3V rail, other than the F28002x device and its corresponding circuitry?

    Are the T_VDDIO-RAMP times different between the two waveforms? I can't tell since the time scale is different. Can you confirm that the VDDIO ramp datasheet spec is met for the case with the drop?

    Best,

    Kevin

    Edit: What is E17 component in the schematic? Not familiar with that symbol.

  • 0 in reply to Kevin Allen18
    TI__Expert 5290 points

    Kevin,

    It is Electrolytic capacitor 100uF/25V.

    BR

    Emma

  • 0 in reply to Kevin Allen18
    TI__Expert 5290 points

    kevin,

    Kevin Allen18 said:
    Can you confirm that the VDDIO ramp datasheet spec is met for the case with the drop?

    checked with customer engineer, the T_VDDIO-RAMP for both is matched with datasheet, which is 10ms at max.

    and they want to know, if the phenomenon can not be canceled, does it will influence F28002X working normally?

    they will go pilot run really soon, and this issue is very important for them.

    BR

    Emma

  • 0 in reply to Emma Wang
    TI__Mastermind 45606 points

    Emma,

    Emma Wang said:
    if the phenomenon can not be canceled, does it will influence F28002X working normally?

    The dip in the waveform looks like it goes into the device's BOR range (< 3.0V). It's possible they will have devices where the BOR trips and the device resets a few times during power up. It's up to their application whether potential BORs at start-up are an issue or not.

    Some notes and considerations we have below for identifying why the 3.3V occurs:

    • This could be related to the 5V supply not powering up fast enough for the 3.3V LDO. The LDO looks like it rises faster than the 5V rail. In this case the dropout voltage spec of the LDO may not be getting met, especially for the lower temp case (where dropout voltages are typically spec'd lower).
    • Possibility of other circuitry on the 3.3V rail suddenly consuming more power

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Expert 5290 points

    Kevin,

    thanks for your kindly suggestion! I have customer to test them.

    Kevin Allen18 said:
    The dip in the waveform looks like it goes into the device's BOR range (< 3.0V). It's possible they will have devices where the BOR trips and the device resets a few times during power up. It's up to their application whether potential BORs at start-up are an issue or not.

    so it means if in their application, there is no extra restrict on start-up precedure.

    then F28002X will work fine with no issues?

    BR

    Emma

  • 0 in reply to Emma Wang
    TI__Mastermind 45606 points

    Emma,

    You're welcome. Received those points and suggestions from others on the team as well.

    Emma Wang said:

    so it means if in their application, there is no extra restrict on start-up precedure.

    then F28002X will work fine with no issues?

    The F28002x will work properly once the power supplies are (and remain) stable and within the datasheet's Recommended Operating Conditions.

    The device could begin executing application code before a reset occurs, depending on how long VDDIO is in operating voltage range before the voltage drop. This may be a problem depending on the application. We would recommend they try and identify the root issue in their system.

    Best,

    Kevin