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TLV709: Clarification on TLV70901 feedback divider current recommendations and design considerations for higher divider current

Conor
Guru 12165 points
Part Number: TLV709

Tool/software:

Hi,

We are currently evaluating the TLV70901 for use in our design, and we would like to confirm a few points regarding the feedback resistor divider configuration.

  1. On page 14 of the datasheet (Table 7-1), the example setting for 5.0 V output uses R1 = 3.16 MΩ and R2 = 1 MΩ. In this configuration, the current flowing through the feedback divider (Vfb ≈ 1.2 V) would be approximately 1.2 μA. However, in section 7.2.2.1 (page 15), it is stated that the resistor divider should be selected to allow approximately 1.5 μA to flow. This seems inconsistent with the example. Is this a mistake in the datasheet, or should we interpret this as a design recommendation rather than a strict requirement?

Also, is it acceptable if the current through the feedback divider is less than 1.5 μA? Conversely, is it permissible to allow more than 1.5 μA through the divider network? The datasheet suggests using R2 = 1 MΩ as a design guideline, but we would like to understand the acceptable range.

  1. In our current design, we are considering using R1 = 150 kΩ and R2 = 24 kΩ to achieve an output voltage of approximately 8.7 V. With these values, the divider current would be around 50 μA (Vfb ≈ 1.2 V / 24 kΩ). Are there any concerns or limitations when designing with such high divider current relative to the recommended 1.5 μA? For example, would this impact regulation accuracy or the stability of the feedback loop?

We appreciate your support in confirming these design points.

Thanks,

Conor

  • +1
    TI__Expert 5301 points

    Hey Conor,

    1. The 1.5 µA figure is a design guideline, not a hard limit. Lower or higher divider currents are acceptable as long as you understand the tradeoffs 

    • Lower than 1.5 µA:
      • Accuracy error increases (IFB / IDIV). Example: at 1 µA, 40 nA leakage introduces 4 % VOUT error worst-case.  The high-impedance node is more sensitive to coupled noise.
      • Startup can become slightly slower because the divider charges through a very high R.
    • Higher than 1.5 µA:
      • Wastes a bit more static current but improves accuracy and noise immunity.
      • No negative impact on stability as long as the output capacitor and ESR stay within the recommended region of the datasheet’s stability curves.

    2.The network you propose is acceptable. The only concern would be the extra 50µA static current on your supply,

    Hope this helps, let me know if you have any more questions

    Thanks,

    Vahnroy