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TL4051A: Can I use the TL4051 like an "upside down" TL431?

Jason Cuadra35
Intellectual 260 points
Part Number: TL4051A
Other Parts Discussed in Thread: TL431

I will be using it in a switching power supply with an inverting feedback input.

TIA

  • 0
    TI__Mastermind 19400 points

    Hi Jason,

    I see your schematic. Can you give me voltage ranges on what you want for Vout and feedback? I am trying to better understand your circuit to give you a recommendation.

    -Marcoo

  • 0 in reply to Marcoo Z
    Intellectual 260 points

    The output voltage is 12V, and the control input range (output of the TL4051 circuit) needs to be 0-5V. 

  • 0 in reply to Jason Cuadra35
    TI__Mastermind 19400 points
    Hi Jason,

    can I see the rest of the circuit schematic?
    I do not understand where the voltage drop will be?
    What are you trying to control with the control input range?
    What do you mean by inverting feedback input?

    -Marcoo
  • 0 in reply to Marcoo Z
    Intellectual 260 points
    "Vout" is the output of a buck converter.
    "feedback" is its control input. Inverting means if you pull it up, the output goes down.
  • 0 in reply to Jason Cuadra35
    TI__Mastermind 19400 points

    Hi Jason,

    Sorry for the delay. Holiday time.

    The schematic is currently incomplete. The TL4051A would require a series resistor on V+ to Vin to regulate properly. I am not sure where Vin is.

    While the TL4051 reference is from Cathode to Feedback, anode does need to be grounded. I would not use  the TL4051 in a forward bias configuration like a diode. I would only use the TL4051 in a reverse voltage configuration like a zener diode.

    The TL4051 will always shunt current.

    The one way I can think of doing this would be to use a TL431 as in the TINA sim attached. If you pull the feedback pin low to GND then Vka goes up high and Voutput goes to ~0V. If you leave Vfeedback High Z so its close to floating, then the output will be based on the resistor configuration. The only issue is that the voltage regulation is based on the 12V rail and not GND.

    e2e.TSC

    -Marcoo