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LM5050-1: [ELENTEC]

MJ Jeon
Genius 5240 points
Part Number: LM5050-1

Hi, TI Support Team

The following inquiries have been received from customers.

I am reviewing the LM5050-1 product and tested with the OUT pin floating for complete turn on of the FET.

At this time, the gate voltage rises to about 4.5V and does not rise any more.

As mentioned above, I want to raise the gate voltage to 12V because I'm aiming for a full turn on of the FET.

Q1. Can the OUT pin be designed in an open state (Floating, see the figure below)?

Q2. When the OUT pin is open, how much does the gate voltage rise?

Q3. What causes the gate voltage to only rise to 4.5V?

Q4. Please tell me how to increase the gate voltage to 12v.

Vin is about 40V.

Thanks.

Regards,

MJ

  • 0
    TI__Guru** 105831 points

    Hi MJ,

    We will get back on this by tomorrow. 

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    TI__Guru 57737 points

    Hi MJ,

    It is not recommended to keep the OUT pin floating. By doing so, you are disabling the reverse current blocking functionality of the IC which is the main feature of this device.

    In case you want to have a device which turns ON the gate fully, consider using LM74801-Q1. This device has  a comparator based gate ON/OFF control and pulls the GATE completely high. 

    For more understanding on this topic, please refer to section '6.1 Linear Regulation Control Vs Hysteretic ON/OFF Control' of  Basics of Ideal Diodes Application Note. 

  • 0 in reply to Praveen GD
    Genius 5240 points

    Dear, Praveen

    Thank you for reply.

    Please refer to the circuit diagram attached below for the part to prevent reverse current.

    It is expected that the reverse current will be solved by applying an external FET.

    Please check how to raise the gate voltage of LM5050 to 4.5V or higher (12V).

    Thanks.

    Regards,

    MJ

  • 0 in reply to MJ Jeon
    TI__Guru 57737 points

    Hi MJ,

    If the OUT pin is left floating, how will you detect reverse current and turn OFF LM5050 Gate ? In case you are going to handle reverse current blocking by any other means, you can make the gate of LM5050-1 high by using a diode between IN and OUT as shown below.

    But we highly recommend using LM74801-Q1 instead of the above work around.