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LM5122: Hiccup mode

Bo Zeng Peng
Prodigy 130 points
Part Number: LM5122

Hello,

I would like to check the hiccup-mode of LM5122. In my application, we would expect LM5122 goes into hiccup protection mode but we also want it can recover from that mode when the overload condtion is removed. In the datasheet, it states that after 8 cycles charge and discharge on RES pin, the controller should restarts. But in  our spice simulation on Tina, I do not see the restart behaviour. 

I want to know if recovery from hiccup over current protection is supported.

I also try to set a cycle on uvlo pin after the overload condition is removed. During simulation, I do not see the recovery of the controller. 

So my question is that if it is possible to recover from hiccup protection and how to achieve that?

Thansk,

Bo 

  • 0
    TI__Mastermind 21720 points

    Hi Bo Zeng Peng,

    Thanks for reaching out with your questions and for considering the LM5122 in your design.

    Yes, the LM5122 will support recovery from hiccup mode operation. As shown in figure 26 of the datasheet when hiccup mode peak current limit detection is triggered the SS pin is pulled low. After the 8 cycles of of the RES pin being charged and discharged the SS pin will begin to rise, and recover the output voltage. If the output short/over load condition is still applied the hiccup mode peak current limit will be trigged again.

    In the simulation, please make sure that the RES pin is connected to a capacitor. This will set the timing for hiccup mode operation. 

    Please let me know if you have any questions.

    Thanks,

    Garrett 

  • 0 in reply to Garrett Roecker
    Prodigy 130 points

    Hi Garrett,

    I do conect the capacitor on RES pin. But after 8 cycles, I do not see the LM5122 back to operation.

    But I will redo the simulation and upload the result here.

    Now I have another question:

    Will shut down cycle on UVLO restart the operation?

    I do the simulation with shutdown cycle on UVLO but LM5122 does not restart. 

    The simulation circuit is shown in the following picture. 

    The siwtch SW1 will close at 100 ms and open at 120 ms.

    The switch SW2 will open at 130 ms and close at 140 ms. 

    But the output voltage does not recover and voltage on SS pin is still low. 

    Best regards,

    Bowebench_design_4621751_96.TSC

  • 0 in reply to Bo Zeng Peng
    Prodigy 130 points

    Hello,

    I did another simulation. I can see the charge and discharge circle on RES pin. But after 8 cycle, I do not see the recovery voltage on output and SS pin keeps low voltage.

    Does the spice model include the recovery from HICCUP mode?

    During simulation, SW1 will close at 40 ms and open at 60 ms.

    The simulation circuit is following.

    Best regards,

    Bo 

    2845.webench_design_4621751_96.TSC

  • 0 in reply to Bo Zeng Peng
    TI__Mastermind 21720 points

    Hi Bo,

    I am looking into the model and will get back to you in a few days.

    Please be aware that the silicon will operate as described by the datasheet. 

    I saw your other post and I don't think for the application that hiccup mode is going to be needed. The RES pin can be tied to ground to disable hiccup mode. This way the large output capacitor can always be charged with out the LM512 entering hiccup mode.

    Please let me know if you have any questions.

    Thanks,

    Garrett 

  • 0 in reply to Garrett Roecker
    Prodigy 130 points

    Hi Garrett,

    Thanks for your reply. I will try to test it on the devkit.

    Best regards,

    Bo

  • 0 in reply to Bo Zeng Peng
    TI__Mastermind 21720 points

    Hi Bo,

    Please let me know if you have another questions. For right now I am going to close the thread, but if anything else comes up please let me know.

    Thanks,

    Garrett