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TLV62095: FB resistance

Hirotaka Matsumoto
Guru 27585 points
Part Number: TLV62095

Hi all

Would you mind if we ask TLV62095?

There is the description "Larger currents through R2 improve noise sensitivity and output voltage accuracy." on the datasheet P13.
By decreasing of FB resistance, feedback current increases.
In this case, we guess as follows;
-Current consumption increases, as the result, the efficiency decrease.
-Responsiveness improves, so, should we note the occilation in case of transient responsiveness?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Expert 3465 points
    Hello Hirotaka,

    Thanks for asking, it's a pleasure to support you!

    Your guesses on increased feedback resistor's current are not totally correct:
    -yes, the efficiency decrease, but it can demonstrated that if your total FB resistance is 1000 times the load current, the efficiency decrease is less than 0.1% (which is comparable with the variations due to the tolerances of the passives i. e.)
    -"Responsiveness improves" is a very general sentence. Maybe you want to refer to the phase margin (which is the one related to oscillations)? If so, It depends. If you are not using a feedforward capacitor (Cff), the FB resistor's influence on the loop is minimal, as soon as you "use a minimum of 5
    µA for the feedback current" (TLV62095 datasheet, pag.13). When you are using a Cff the story is different, because the frequency of the pole-zero couple introduce by it depends also on the values of the FB resistors. So, the smaller they are, the higher the pole-zero. To compensate this shifting and maintain the position, Cff must be higher.

    I hope my explanation is clear, but you are welcome to ask for any other clarification.