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LM73605: About short circuit protection

Tsukui Yusuke
Guru 21930 points
Part Number: LM73605
Other Parts Discussed in Thread: LM76003, LM73606EVM-5V-400K

Hi,

Could you tell me about LM73605 overcurrent and short-circuit protection?

Now we're competing with LT8614.
Customer is expecting a function of the following wording in LM73605/6.

"During overload or short-circuit conditions the LT8614 safely tolerates operation
with a saturated inductor through the use of a high speed peak-current mode architecture."

Customer wants to use an inductor whose rating is lower than the current limit value.
Therefore, such a function is indispensable.
Is it possible to achieve this in the LM73605/6?

Customer usage example:
Vin=19.5V,Vout=5V,Iout≒3.6A, Used Inductors  in combination with LT8614 = FDSD0420-H-2R2M


Best Regards,
Yusuke

  • 0
    TI__Genius 11040 points
    Hello Yusuke-san,

    The LM73605/6 will enter into hiccup protection. The device will shut off and reattempt soft-start after approximately 46ms. Once the short is removed the device will start up again. This will prevent the device from heating up during short circuit operation.

    This will partially depend on the inductor paired with the LM73605/6. With a soft saturation current (not hard which turns to a short) then a lower saturation current can be used.

    I would also recommend using a device with a lower maximum output current for this application. Two options would be the LM53635 or the LM76003.

    Please let me know if you have any additional questions.

    Best Regards,
    Katelyn Wiggenhorn
  • 0 in reply to Katelyn Wiggenhorn
    Guru 21930 points

    Katelyn-san,

    Thank you for your response and support.
    I conducted a short circuit test with evm to check the behavior of the soft saturation current pattern.
    I will write test conditions. And Attach the test situation.

    □Vin=19.5V,Vout=5V,Fsw=500kHz, L: FDSD0420-H-2R2M, EVM:LM73606EVM-5V-400K
    □Test situation
    LM73606 test condition.pdf

    The device broke a few seconds after starting the test.
    Can this device withstand short circuit tests when the inductor is saturated?

    I propose LM73605/6 for replacing LT8614.
    LT can clear the short test even when L is saturated.
    Could you give me your advice and support?


    Best Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Genius 11040 points
    Hello Yusuke,

    Since we have continued the conversation through e-mail, I am going to close this thread.

    Best Regards,
    Katelyn
  • 0 in reply to Katelyn Wiggenhorn
    Guru 21930 points

    Hello Katelyn-san,

    I appreciate your cooperation.
    I will check email with shidara-san.

    Best Regards,
    Yusuke