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LMZM33603: WEBENCH Recommended Schematic for LMZM33603

Part Number: LMZM33603
Other Parts Discussed in Thread: LMR38020, LMR36520

Hello,

I'm reaching out for support regarding an inverting application using the LMZM33603. I've utilized the WEBENCH tool for my design, and there are two points of concern where I could use your guidance:

1- As observed in the attached screenshots from the WEBENCH application, the EN pin of the LMZM33603 is left floating. However, the documentation advises against leaving this pin unconnected. Could you provide insight into why WEBENCH suggests this configuration and how it might impact the performance or reliability of the application?

2- The switching frequency is calculated by WEBENCH to be approximately 750kHz, as seen in the visuals. Typically, I would expect to select this frequency via the RT pin in the schematic, yet the RT pin is left floating in this design. Could you clarify why this might be the case and if there's an aspect of the configuration I might be overlooking?

3- Additionally, I believe the recommended schematic might exceed the LMZM33603's maximum voltage limit. (42V in total)

Thank you for your assistance. I'm looking forward to your expert advice on these matters.

Best regards.

  • Hi Harun,

    Yes for 27V to -15V/1A application, a device with minimum 42V Vin can work. Suggest you can design with LMR36520 or LMR38020. 

    You can also refer to this application note for the design of IBB. Link here

    Regards,

    Hongjia