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LM5021: Cut off LM5021 OUT from following circuit

Sambhav Deshmukh
Prodigy 60 points
Part Number: LM5021

We are using LM5021MM-2 NOPB PWM IC in a flyback circuit. 

 

We are planning to  disconnect PIN4 from the following circuit which is a MOSFET gate by using a transistor and a soft signal to turn of the flyback.

 

We need a clarification on if this is practically possible or not. And challenges we may face doing so.

 

Also let us know if you any other verified solutions to turn OFF flyback using a 5V signal.

  • 0
    Prodigy 60 points

    Pin 4 is the output of IC LM5021 and there is 6.8 ohm resistor in series which is then connected to gate voltage of MOSFET. If another MOSFET is connected as shown in image then, will U1 turn of ?

    Please let me know if it is possible practically?

  • 0
    Prodigy 60 points

    Pin 4 is the output of IC LM5021 and there is 6.8 ohm resistor in series which is then connected to gate voltage of MOSFET. If another MOSFET is connected as shown in image then, will U1 turn of ?

    Please let me know if it is possible practically?

  • 0 in reply to Sambhav Deshmukh
    TI__Genius 17935 points

    Hello Sambhav,

    Thank you for your patience. Based on the diagram you have shown me, U1 will not turn on.The first MOSFET you have it connected to (BSS138) will short U1. It is not practically possible as it will damage parts and this configuration will only short Pin 4, not disconnect it. 

    The TI Reference Design Library,(TI Reference Designs Library), may be able to assist you as well. 

    Best Regards,

    Alexis