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WEBENCH® Tools/LMZ12003: quick voltage drop and power supply incompatibility

Stefan Langer1
Prodigy 20 points
Part Number: LMZ12003

Tool/software: WEBENCH® Design Tools

Hello,

we are using LMZ12003TZ-ADJ/NOPB 9.0V-17.0V to 5.00V @ 2.0A as power supply for a single board computer application. We use the schematics and circuit board layout from the Webench (as far as possible). Unfortunately we have some problems:

1. On some 12V power supplies the single board computer does not boot. The LMZ12003 outputs voltage, so that the LEDs of the SBC are turned on and also the backlight LEDs of the display. When using a 12V battery there is no problem.

2. When the input voltage of the LMZ changes quickly, e.g. an other big consumer load is turned on at a battery application, the SBC turns off immediately. After a few seconds the SBC boots again when the same load and voltage level is applied.

Do you have any recommendations how to improve these behaviours?

Thanks and best regards, Stefan

  • 0
    TI__Guru 50120 points

    Hi Stefan,

    Can you provide the webench share design or your schematic for review? Regarding your first question, can you probe the feedback pin and check if it is roughly 0.8V for both 12V power supply and 12V battery? 

    The LMZ12003 should not have any issues with varying input voltage because the device is tested for line regulation at full load and should still provide a stable output.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Prodigy 20 points

    Hi Jimmy,

    thank you for the quick reply.

    Please find attached the schematics, PCB layout and BOM.

    I failed replicate the power supply issue, because all our own power supplies work fine. There I measured the feedback pin and it´s between 0.79 V and 0.80 V, so that´s fine.

    Best regards,

    Stefan

    1732.schematics.pdfAdapterboard_SF_V34.zip

  • 0 in reply to Stefan Langer1
    TI__Guru 50120 points
    Hi Stefan,

    I've taken a look at the files and don't see anything that pops out that could be causing the issue that you are describing. Can you confirm that the power supply that doesn't work is not current limited in any way? What is the difference in power supply between when the board doesn't work and your own power supply that works fine?

    Regards,
    Jimmy
  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points

    Hi Stefan,

    I haven't heard back from you so I assume you were able to resolve your issue. If not, please reply below. 

    Regards,

    Jimmy