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LM2673: 5V output from12V variant

Marvn Arcangel
Genius 14240 points
Part Number: LM2673
Other Parts Discussed in Thread: LMR33630, LM22673,

Hi Team,

The customer is using LM2673SX-ADJ/NOPB and would need an output of 5v, however, both LM2673SX-ADJ/NOPB and LM2673SX-5.0/NOPB are currently out of stock in their region. The use of alternative LMR33630 is not acceptable for the customer since it will generate a lot of design modifications on their part. 

Their idea is to use an LM2673SX-12/NOPB (which is available in their region) and then convert the 12V output to 5V by using resistors. I suggested adding a voltage divider to the output of LM2673SX-12/NOPB and use the Voltage Divider Calculator available on the TI website. Can you confirm that my suggestion is okay?

Suggested:

Customer design:

Thanks!

Regards,

Marvin

  • 0
    TI__Mastermind 19911 points

    Hello Marvin,

    Unfortunately, I don't think any of these two examples would work. 

    The LM2673-12 already includes internal FB resistors so the feedback voltage is regulated at 12V. They won't be able to generate lower voltages as-is. 

    The resistor divider after the regulator to "step down" the voltage is not a good suggestion. The voltage will heavily depend on the load. 

    Regards, 

    Denislav

  • 0 in reply to Denislav Petkov
    TI__Genius 14240 points

    Hi Denislav,

    Thank you for the correction. Do you have any suggestions on how can the customer can achieve this? a similar product with a similar package would be a great help.

    Regards,

    Marvin

  • 0 in reply to Marvn Arcangel
    TI__Mastermind 19911 points

    Hi Marvin, 

    The LM22673 is a slightly newer version of this family. It switches at higher frequency so some adjustment of the inductor and output capacitor may be necessary. If they are using the TO-263 version of the LM2673, then the LM22673 may be able to fit on the same footprint. 

    Regards, 
    Denislav