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TPS62290-Q1: is it ok to choose smaller divider resistors

Hi team,

My customer uses below application. And I have two questions as below,

1. They want to use smaller resistor, R1=150k, R2=33k, is it ok? Then if they use these two resistors, could you please recommend the C1 value? 33pF?

2. As we know, the larger the divider resistance, the worse the immunity. If we choose R1=360K, R2=180K, how about the immunity?

Could you please help answer above two questions?

Thanks & Best Regards,

Sherry

  • Hi sherry,

    1.We recommend designing according to the datasheet,  which recommond using 180K or 360k resistor for R2 and the C1 is between 22pf to 33pf. You can change the resistor and CFF according to below application not, but we don't guarantee its performance .http://www.ti.com/lit/an/slva289b/slva289b.pdf 

    2. could you please explain the meaning of immunity, you can refer to the load transient result on datasheet PIC17~20.

    Best Regards,

    Kevin

    If this answers your question, Please click "This resolved my issue" button.
    ____________________________________________
    TPS62810-Q1 – New Automotive 6Vin, 2.25MHz buck family with 1% accuracy and SYNC-pin. 1-2-3-4A options.
    Smallest 2x3QFN package with wettable-flanks for optical PCB inspection.

  • Hi Kevin,

    The immunity means the ability to resist interference(抗干扰性).If the feedback resistor is large, it will be very susceptible to interference, isn't it?

    Thanks & Best Regards,

    Sherry

  • Hi Sherry,

    Yes,it is right, so we have limits on that.

    Best Regards,

    Kevin

    If this answers your question, Please click "This resolved my issue" button.
    ____________________________________________
    TPS62810-Q1 – New Automotive 6Vin, 2.25MHz buck family with 1% accuracy and SYNC-pin. 1-2-3-4A options.
    Smallest 2x3QFN package with wettable-flanks for optical PCB inspection.

  • Hi Sherry,

    Yes,it is right, so we have limits on that.

    Best Regards,

    Kevin

    If this answers your question, Please click "This resolved my issue" button.
    ____________________________________________
    TPS62810-Q1 – New Automotive 6Vin, 2.25MHz buck family with 1% accuracy and SYNC-pin. 1-2-3-4A options.
    Smallest 2x3QFN package with wettable-flanks for optical PCB inspection.

  • Hi Kevin,

    If the feedback resistors are smaller, what performance will be affected in addition to efficiency? I know this will reduce the efficiency, but my customer doesn't care about the efficiency, they only cares about the ability to resist noise.

    Now they want to use smaller resistor to improve chip's ability to resist noise, is it ok? Assume that a small resistor has only one disadvantage, that is the efficiency.  If I don't care about the efficiency, then I can use the smaller resistors, right?

    Is my assumption right? Below picture is my customer's feedback. 

    Looking forwarding to your reply!

    Thanks & Best Regards,

    Sherry

  • Hi Sherry,

    For the influence of resistor divider, you can refer to this application note: http://www.ti.com/lit/an/slyt469/slyt469.pdf

    You can use smaller resistor, at the same time you need to change the value of CFF according to this application note :http://www.ti.com/lit/an/slva289b/slva289b.pdf 

     Due to the change,  we don't guarantee its performance matches datasheet.

    Best Regards,

    Kevin

    If this answers your question, Please click "This resolved my issue" button.
    ____________________________________________
    TPS62810-Q1 – New Automotive 6Vin, 2.25MHz buck family with 1% accuracy and SYNC-pin. 1-2-3-4A options.
    Smallest 2x3QFN package with wettable-flanks for optical PCB inspection.