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TPS53355: Possibility of having Vout lower than 0.6V

Oussama HADDAD
Prodigy 110 points
Part Number: TPS53355

Hello,

My question is about the possibility of having Vout lower than 0.6V,

Let's say that I need an output of about 0.25V

the VFB input is compared inside the chip with the reference (0.6V), to adjust a PWM which adjust in its turn the output voltage,

Let's say that I choose the external components to have 1V output (for example). and I add a stage at the VFB that multiply the voltage by 4 

So th VFB will be 4V.

In this case, will the DC DC converter adjust the PWM to have an output voltage of 0.25V (1V/4)?

I attached an image to more explain the question.

thanks.

  • 0
    TI__Guru 72785 points

    Although theoretically it might be work, I do not think it is a good idea.

    Placing anything in the feedback loop of the regulator an cause instability.

    Also, you may have issues with min on-time with such a low output voltage depending on you input voltage.

    You can experiment by lifting up the bottom FB resistor and putting a voltage on that node and adjusting

    for you output voltage.

  • 0
    TI__Guru**** 191445 points
    I'll look at this later today or tomorrow and let you know.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points
    Theoretically you could use an external error amplifier and configure it so that its output equals 0.6 V when the input equals whatever lower voltage you are trying to achieve. Another approach would be to inject current into the FB node. You can do that with a resistor between VFB and an appropriate voltage source.