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LM51521-Q1: What is "HB-SW short protection" and how is it achieved?

Part Number: LM51521-Q1

Hi team, 

What is "HB-SW short protection" and how is it achieved?

In addition, do you have LM51521-Q1 EVM instead of LM5152EVM for BUB solution?


  • Hi Ochi,

    Thank you for using E2E forums, Please allow us some time to get back to you regarding this.

    Thank you for your pateince



  • Hello Ochi,

    If there is a short between the HB pin and the SW pin and CHB cannot be charged, the following happens: 

    The hiccup mode fault protection is triggered by the HB UVLO.
    If the HB-SW voltage is less than the HB UVLO threshold (VHB-UVLO), the LO turns on by force for 75 ns to replenish the boost capacitor.
    The device allows up to four consecutive replenish switching.
    After the maximum four consecutive boot replenish switching, the device skips switching for 12 cycles.
    If the device fails to replenish the boost capacitor after the four sets of the four consecutive replenish switching, the device stops switching
    and enters 512 cycles of hiccup mode off time. During the hiccup mode off time, SS is grounded.



  • There is no separate EVM for the LM51521. Please use the LM5152 EVM and replace the part.