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LM5161: Protection mode

Michiaki Tanii
Expert 4560 points
Part Number: LM5161

Hi team,

 

Could you kindly advise the conditions to recover from any protection ?

Please check customer’s understanding as following.

 

  1. Shutdown (V_EN/UVLO < 0.35V typ) -> Exceeding VCC(UV) and 1.24V at EN/UVLO pin ?
  2. Standby (V_EN/UVLO < 1.24V typ and > 0.35V typ) -> Exceeding VCC(UV) and 1.24V at EN/UVLO pin ?
  3. VCC UVLO -> Exceeding VCC(UV) 3.98V ?
  4. H-side current limit protection (> Typ 1.61A) -> Pass TOFF(CL) ?
  5. L-side current limit protection / source (> Typ 1.6A) -> Customer cannot find the description.
  6. L-side current limit protection / sink (> Typ 3.0A) -> Customer cannot find the description.
  7. Thermal shutdown (Tj > 175C typ) -> Falls below 155 C
  8. If there are another protection, please let me know.

 

Thank you and best regards,

Michiaki

  • 0
    TI__Mastermind 27045 points

    Hi Michiaki,

    I will check and update you later.

    B R

    Andy

  • 0 in reply to Andy Chen
    TI__Mastermind 27045 points

    Hi Michiaki,

    1. Shutdown (V_EN/UVLO < 0.35V typ) -> Exceeding VCC(UV) and 1.24V at EN/UVLO pin ?-----YES
    2. Standby (V_EN/UVLO < 1.24V typ and > 0.35V typ) -> Exceeding VCC(UV) and 1.24V at EN/UVLO pin ?------YES
    3. VCC UVLO -> Exceeding VCC(UV) 3.98V ?-------YES
    4. H-side current limit protection (> Typ 1.61A) -> the present ON-time period is immediately terminated, followed by TOFF period
    5. L-side current limit protection / source (> Typ 1.6A) -> inductor current peak is limited by HS switch, low side FET is free wheel path of inductor current, so no need to limit the source current on  L-side FET
    6. L-side current limit protection / sink (> Typ 3.0A) -> Only limit sink current peak at FPWM mode, turn-off L-side FET immediately if trig the limitation.
    7. Thermal shutdown (Tj > 175C typ) -> Falls below 155 C------YES
    8. If there are another protection, please let me know.----BST also has UV protection, exceed 2.93V enable switching

  • 0 in reply to Andy Chen
    TI__Expert 4560 points

    Hi Andy,

     

    Regarding low side current limit protection by skink current, please kindly advise the condition of recovery ?

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 27045 points

    HI Michiaki,

    L-side current limit protection / sink (> Typ 3.0A) -> Only limit sink current peak at FPWM mode, turn-off Low-side FET immediately if the sink current trig the limitation 3A, then HS FET will be turn-on.

     

    B R

    Andy

  • 0 in reply to Andy Chen
    TI__Expert 4560 points

    Hi Andy,

     

    It means that even if only the sink current limit is triggered, LM5161 only turns on HS FET and will not stop SW operation.

    In other words, LM5161 will stop SW operation only if source current limit at HS FET is triggerd.

     

    Is my understanding correct ?

     

    L-side current limit protection / source (> Typ 1.6A) -> inductor current peak is limited by HS switch, low side FET is free wheel path of inductor current, so no need to limit the source current on L-side FET

     

    Regarding the above, why is sourcing current limit at LS FET specified ?

    Please give us background information on the above.

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 27045 points

    Hi Michiaki,

     if the low-side sink current limit is triggered, LM5161 only turns on HS FET and turn-off low side FET, not stop SW operation.

    In other words, LM5161 will turn-off high-side FET once source current limit at HS FET is triggerd, HS will be turn-on again at next cycle

    After HS is turn-off, inductor current can't be changed and will flow in loop of output and low-side FET, so no need to limit the source current on L-side FET as it's limited by high-side FET when HS is turn-off

    B R

    Andy