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Original question:

TPL7407L: TPL7407L

TPL7407L: TPL7407L

Daniel Adolf
Prodigy 20 points
Part Number: TPL7407L

In the meantime I made some tests regarding this Topic and I had the following idea.

Here you can see the control of the fan. Yellow is the PWM Signal and purple is the FAN ON/OFF Signal. In the off state of the fan there is always a pwm. Assuming we have an emc issue and the always on pwm could this be the reason of the failure or the damage?

  • 0
    TI__Genius 13300 points

    Hello Daniel,

    Could you show the schematic surrounding the TPL7407L? I just want to confirm my understanding- you're saying you have the PWM(yellow signal) on the input of the TPL7407L and the fan on the output, but the fan itself has an on/off switch which is the purple signal? 

    Regards,

    Kalin Burnside

  • 0
    Prodigy 20 points

    Hello Kalin,

    sorry for the missing schematic. I have made another post with the same problem a few moth ago. I just wanted to add a new related question, but it was not possible.

    You are Right:

    Yellow = PWM

    Purpe: on/off Signal

    BR

    Daniel

  • 0 in reply to Daniel Adolf
    TI__Genius 13300 points

    Hello Daniel,

    Are you able to get a scope shot with output current as well? Also, could you not test whether the device is damaged from your assumption by leaving the fan ON and observing the event? 

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Prodigy 20 points

    Hello Kalin,

    i will scope the current. The other Topic is not possible, because we are switching on the fan and the failure occures at the customer side. It was not possible to reproduce the failure in the lab.

    Could it be possible that the TPL will be destroyed by the inrush current of the fan? The manufacturer of the fan did some measurements with the result of about 5,728A over 4,5us? Is this ok for the internal mosfet?

    BR

    Daniel Adolf

  • 0 in reply to Daniel Adolf
    TI__Genius 13300 points

    Hello Daniel,

    Thank you for providing the inrush current. I will need to get in touch with my team to see if it's possible that this short transient event could damage the device. I'll be in touch before the end of the week.

    Regards,

    Kalin Burnside 

  • 0 in reply to Kalin Burnside
    TI__Genius 13300 points

    Hello Daniel,

    It is unsurprising if the inrush current is causing the damage since each channel is rated to 600mA. If your PWM control is independent of your power on control you can use a by-pass capacitor on the PWM power node to provide the inrush current, so that the majority of the current comes from that. You could also combine channels to handle the inrush current.

    Regards,

    Kalin Burnside