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UCD3138: Reset condition after starting UCD3138

Masazumi Ishii
Genius 3945 points
Part Number: UCD3138


Hello.

I have a question about UCD3138 RGCT.

１　Please tell me all the conditions for RESET operation after normal start (operation).

２　When the voltage difference between DGND and AGND becomes 0.3 V or more,What kind of problem will you encounter?

Thank you.

  • 0
    TI__Mastermind 18370 points

    1) After power up the VDD should go below VGL in order for the device to reset.

    For more details please look at the section: "5.7 Power SupplySequencing" in the data sheet:

    www.ti.com/.../ucd3138.pdf

    2) The voltage difference between DGND and AGND should stay zero (minimal) at all times.

    That is why we recommend single ground plane in layout around UCD3138.

    For more details please review the UCD3138 Practical Design Guidlines:

    www.ti.com/.../slua779a.pdf

    Regards,

  • 0 in reply to Yitzhak Bolurian
    Genius 3945 points

    Hi.
    Yitzhak-san

    Thank you for answering.

    It is confirmation again.
    Is it only when the VDD is lower than VGL that the reset takes place after startup?
    Is there any other understanding that there is nothing?

    Thank you.

  • 0 in reply to Masazumi Ishii
    TI__Genius 17090 points

    The UCD is also sensitive to power supply and other noise.  This can cause reset as well.  We have some layout and power supply capacitor guidelines to help prevent this in the Practical Design Guidelines that Yitzhak linked to above. 

  • 0 in reply to Ian Bower
    Genius 3945 points

    Hello.

    I have additional questions on UCD3138.

    It was pointed out that there is a possibility of being reset by noise.

    In the previous reference layout, AGND and PGND were taken from separate GND lines, but AGND and PGND have been changed to connect to solid GND at the latest.
    Is there a reason?

    Also, please tell me the guidelines. (Please have it if there is material.)
    Thank you.

  • 0 in reply to Masazumi Ishii
    TI__Mastermind 18370 points
    Depending on how many layers your PCB consist of, the previous reference layout may work as well.
    But our experience with all derivatives of UCD3138 shows that a unified GND plane offers a more versatile solution.

    But this is not the only thing to follow.
    There are several helpfull tips in the document below that need to be carefully followed:

    www.ti.com/.../slua779a.pdf

    Regards,