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LM5122: Transfer function clarification

Jejomar Ildefonso
Genius 9500 points
Part Number: LM5122

Hi Team,

Need your clarifications for this query from our customer. The feedback transfer function of LM5122 was defined as -V_COMP / V_OUT on page 26 of the datasheet, which was the same with the feedback transfer function of Table 2. However, the open loop response formula on the same table does not have this negative sign. The function was positive instead. Can you help us with the reason for the difference? When simulating the system, should they use the positive or negative transfer function?

Thanks in advance!


Kind Regards,

Jejomar

  • 0
    TI__Expert 7450 points

    Hi Jejomar,

    The feedback transfer function Vcomp/Vout should be negative by definition because it's negative feedback. The open loop formula, T(s), should be positive. This is also how it's defined.

    As for the simulation, what kind of simulation are they doing? If it's circuit-based, they don't need to worry about the sign because the model on TI.com already accounts for that.

    Please let me know if there is any question.

    Thanks,
    Yinsong