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LM3409HV: The design issue for LM3409HV

Zhang Liang
Genius 4125 points
Part Number: LM3409HV

Tool/software:

Hi,

We are use the LM3409HV for the LED driver, the output current is 3.5A max., 

Now, the LED are turn on when the power on, and the LED will be turn off after 10mins, and we pull down the EN about 10s, the LEDs are turn on normally.

Plesae refer to below schematic diagram and advise how to solve this issue, thanks.

5775.LM3409HV.pdf

  • 0
    TI__Expert 3470 points

    Hi Zhang, 

    Sounds to me like the device is entering thermal shutdown. The threshold for thermal shutdown is 160°C with 15°C of hysteresis (both values typical). During thermal shutdown the PFET and driver are disabled. Does this phenomena if the IC is actively cooled?

    Thanks,

    Jaron

  • 0 in reply to Jaron Wilson
    Genius 4125 points

    Hi Jaron,

    The switching speed of the shunt NMOS is proportional to the value of the inductance.
    After the inductance increases, during the high level time of the NMOS, the LED is in the charging process (that is to say, the LED is not in the off stage).
    But if the inductance is too small, the LED will have a relatively long charging  time when the NMOS is turned on (which we don't want).
    So I hope you can help us configure the components or parameters.

    The switching speed of the shunt NMOS is proportional to the value of the inductance. After the inductance increases,

    during the high level time of the NMOS, the LED is in the charging process (that is to say, the LED is not in the off stage).

    But if the inductance is too small, the LED will have a relatively long charging time when the NMOS is turned on (which we don't want).

    So I hope you can help us configure the components or parameters.

  • 0 in reply to Zhang Liang
    TI__Expert 3470 points

    Zhang,

    I don't understand what is being asked here. Is this related to your original question or a new issue altogether? Can you be more specific?

    Thanks,

    Jaron

  • 0 in reply to Jaron Wilson
    Genius 4125 points

    Hi Jaron,

    Sorry, I mean can you help to promote the MOFSET and inductance spec. that we can aviod the MOSFET thermal shutdown issue, the below is the

    schematic diagram, thanks.

    2746.LM3409HV.pdf

  • 0 in reply to Zhang Liang
    Genius 4125 points

    Hi Jaron,

    Please kindly help to provide the MOFSET and inductance spec. to us that we can choose the suitable device for this design, thanks.

  • 0 in reply to Zhang Liang
    TI__Expert 3470 points

    Hi Zhang, 

    I still don't understand what you are asking. This device is a MOSFET controller there is no internal MOSFET and I'm not sure what inductance spec you are referencing. Please review datasheet section 9.2 Typical Applications and you can see some examples of different FETs used for different applications. 

    Thanks,

    Jaron