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LM5060-Q1: C1 Turn-On Time Extension

hideyuki sakai
Mastermind 6250 points
Part Number: LM5060-Q1
Other Parts Discussed in Thread: LM5069

Dear, Sir.

I would like to make sure about the turn-on time extension using C1 capacitor.

Sorry to disturb your jon. Please give your advice.

1. Is there a recommendation value or limitation on the value as C1 capacitor?

2. The datasheet explains the damage due to peak power loss on slow turn on.

    Too much capacitor value will influence at turn off time also because the higher Gate

    voltage will remain long time against lower Vin voltage.

    I wonder my guess is correct?

Best Regards,

H. Sakai

  • 0
    TI__Guru** 102661 points

    Hi Sakai,

    1. You can use capacitance up to ~22nF on the GATE. Beyond that I would recommend to use "external dvdt circuit mentioned in the first page of LM5069 datasheet".

    2. Higher the GATE capacitance, longer the startup time. It helps by minimizing the inrush current for purely capacitive load. For constant power or constant current loads, longer startup time would stress the MOSFET.

    Can you share your application details. Is it for automotive.? what are the system specs?

    BR, Rakesh

  • 0 in reply to Rakesh
    Mastermind 6250 points

    Dear, Rakesh-san. 

    Thank you so much for your advice. 

    I tried to check using the simulation model to add 22nF capacitor on GATE. 

    It looks the gate voltage is clamped by the internal 16.8V zener at turn off time. 

    I wonder this behavior will be expected as the normal & reasonable?

    Please give your advice one more time. 

    PS) 

    It is automotive & related to RMA case you know. The running is 30k.month. 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Guru** 102661 points

    Hi Sakai-san,

    When the supply Vin =0, the GATE should be fully discharged.

    Do you mean error in the simulation file ?

    BR, Rakesh

  • 0 in reply to Rakesh
    Mastermind 6250 points

    Dear, Rakesh-san. 

    Thank you so much for your reply. 

    I will send my message for your private mail attaching the confidential

    information. Shall we talk via private mail. 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Guru** 102661 points

    Hi Sakai-san,

    Closing thread here as we are taking discussion forward on email.

    BR, Rakesh