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TLV709: About Feedback Current

Ryu Yamashita
Genius 3705 points
Part Number: TLV709

Tool/software:

Hi team,

Can you tell me the IFB for this device?
I could not find any description in the datasheet.
Also, it says to select a feedback resistor R2 of 1MΩ or more, but if this is too low, is there any problem?
I read that if the resistor is too small, the current consumption will go up.
Are there any other problems?

Best Regards,
Ryu.

  • +1
    TI__Guru 50025 points

    Hi Ryu,

    I'm not sure why the IFB wasn't spec'd, but we can infer that the IFB current is less than 1.5uA / 100 = 15nA (max) because we normally recommend sizing the feedback resistors such that there is at least 100x the current through them to avoid inaccuracies due to the IFB leakage current. The recommendation to use a bottom resistor of 1MΩ is to help optimize the performance of the device to retain its accuracy while minimizing the biasing current drawn to operate the device. If you are not using a feedforward capacitor, then the only substantial difference in using a smaller resistor is that (as you mentioned) the current through the feedback divider increases and so the overall current consumption goes up. If you are using a feedforward capacitor, the relative sizes of the resistors along with the size of the feedforward capacitor determine where the zero and pole are.

    Regards,

    Nick