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LMZ31520: LMZ31530 and LMZ31520 ILIM adjustment formula

Kazuhiko Hirano
Genius 11613 points
Part Number: LMZ31520
Other Parts Discussed in Thread: LMZ31530

Hello,

Due to delivery issue recently, my customer plans to replace LMZ31530 by LMZ31520, since Iout(max) = <20A at their design.
They would like to adjust current limit so that it will be the same value on both modules.
Could you tell them how to calculate the current limit by RILIM at LMZ31530 and LMZ31520 respectively, please?

And, any other things to take care about the replacement?

Best regards,

K.Hirano

  • 0
    TI__Expert 5310 points

    Hello,

    In both datasheets, the current limit in the electrical characteristics table can be reduced by a certain percentage based on the resistance selected from table 6. 

    Do you happen to know the approximate current limit the customer wishes to set using the LMZ31520? I would be happy to provide the value if so. 

    In the case of calculating the current limit, I would use a proportion with the values in table 6 as a reference.

    Regards,

    Alec Biesterfeld 

  • 0 in reply to Alec Biesterfeld
    TI__Genius 11613 points

    Alec,

    Thank you for your response.

    Current customer LMZ31530 design is Iout(max)~=14A, and RILIM=825Kohms.
    What if they replace LMZ31530 by LMZ31520 with the same peripheral components?

    What would be ILIM at LMZ31520 with RILIM=825Kohms?

    What else should be also considered to replace LMZ31530 by LMZ31520?
    Any other component changes to be considered when replacing LMZ31530 by LMZ31520 at their current design?

    Best regards,

    K.Hirano

  • 0 in reply to Kazuhiko Hirano
    TI__Expert 5310 points

    Hello,

    Using an 8256kohm resistor with the LMZ31530 reduces the current limit identified in the electrical characteristics table by 10% as noted in table 6 of the datasheet. This means that the overcurrent protection in the current design is set to 36A. The LMZ31520 supports a maximum current limit of 30A. I may suggest a 243kohm resistor, which will set the overcurrent protection to 21A using the LMZ31520. 

    In regards to the external component selection, there are no additional changes required when moving from the LMZ31530 to the LMZ31520 other than the current limit setting.

    Regards,

    Alec Biesterfeld