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TPS54320: TPS54320 sink current limit definition

Mark Chen52
Expert 8045 points
Part Number: TPS54320

Hi Expert,

I saw the sink current limit show in Electrical Characteristics table of datasheet page 6, could you share more the sink current behavior and what's the condition to trigger sink current protection?

Best Regards,

Mark

  • 0
    TI__Mastermind 35185 points

    Hi Mark,

    Please review the section of the datasheet titled 7.3.15.2 Low-Side MOSFET Overcurrent Protection that describes this. Conditions that may be trigger this protection are ones where the output voltage is higher than what the part is trying to regulate the output to. In these scenarios the part will try to sink current to bring the output voltage into regulation. The usual scenario this could happen is after the output overshoots from a large load step down.

    The sinking current limit could also be tripped if an external voltage source forced the output voltage above the regulation voltage. However this is not something that should normally be happening in most applications.

    Anthony

  • 0 in reply to Anthony F
    TI__Expert 8045 points

    thanks Anthony,

    is it just like Body breaking protection? which is reduce the Vout overshoot and to improve transient response?

    if the ripple current of inductor is too large, maybe like peak to peak 6A, is it will be trigger sink current limit under without load condition? due to the negative current of inductor will be 3A. 

    is it correct of my understanding?

    Best Regards,

    Mark

     

  • 0 in reply to Mark Chen52
    TI__Mastermind 35185 points

    Hi Mark,

    The sinking current limit here would not be like body braking. Body braking turns off the LS FET while the inductor current is positive and the drop across the LS FET body diode helps the inductor current ramp down quicker. The sinking current limit of the TPS54320 turns off the LS FET while the inductor current is negative. The sinking current limit of the TPS54320 is meant to limit the amount of current the device sinks in order to protect it.

    The sinking current limit could take effect with too much inductor ripple so it should definitely be considered when selecting the inductance. The ripple current should be kept less than 2 A p-p to avoid hitting the 1 A minimum sinking current limit.

  • 0 in reply to Anthony F
    TI__Expert 8045 points

    Got it and thanks Anthony.

    Regards,

    Mark