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LM5122: LM5121 replace LM5122

Part Number: LM5122
Other Parts Discussed in Thread: LM5121

Hi Team,

Our customer got LM5122 shortage and tried use LM5121 to replace, customer would like confirm with us if LM5121 can direct replace LM5122 by floating Pin1/Pin2?

Appreciate your suggestions and comments,

Thanks & Regards

Eddie

  • Hi Eddie,

    Thank you for using E2E forums, Regarding your question, LM5121 Provides the disconnection switch control which gives inrush current limit and stronger protection, whereas LM5122 is used for multiphase application for higher power and output current. LM5122 and LM5121 are practically same in terms of boost operation, the main difference is as you pointed out the pin 1 and 2, in LM5122 they are used to configure multiple LM5122 in parallel to support high power application, whereas LM5121 uses it for inrush current limiting.

    You can replace LM5122 with a LM5121, and if you do not want the inrush current limit protection feature of the LM5121 and want to remove the Qd MOSFET, then please place a 100pF capacitor in between the DG and DS pin (pin 1 and 2) and then place a 500kOhm resistor from DS pin to GND if disconnection switch is not used.  

    BR,

    Haroon

  • Hi Haroon,

    Thanks a lot for your support, attached is customer LM5122 schematic, can customer direct change to LM5121 without change PCB layout?

     

    Thanks & Regards

    Eddie

  • Hi Eddie,

    If the PCB layout worked and was fitting for LM5122, it should also work with LM5121 as well, if you want me to review the schematic design in fully, please send me the full image of the design alongside the design specs Vin, Vout etc.

    BR,

    Haroon