• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 338 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS7B4253-Q1: Acceptable Cfb(capacitor between out and FB pins) value

Shota Mago
Expert 6580 points
Part Number: TPS7B4253-Q1
Other Parts Discussed in Thread: TPS7B4253EVM

Hi team,

My customer will employ TPS7B4253 and he provided a question.

His question is "What is acceptable capacitor value between out-pin and fb pin?"

My customer is designing refer to Figure.25(please see below figure).

It shows just 47uF seems to be for phase compensation.

Is it possible to change that value to 0.1uF?

or is there any tool to simulate TPS7B4253 stability?

I'm looking forward to hearing back from you.

Best regards,

Shota Mago

 

  • 0
    TI__Guru 55940 points
    Hi Shota,

    A feedforward capacitor can help improve stability, output noise, load transient response, and PSRR. As noted the TPS7B4253-Q1 recommends a 47 nF feedforward capacitor when the desired output voltage is greater than the reference. A 0.1 uF capacitor may be suitable for your specific application; however, prototyping is recommended before committing to the change. The following Application Report goes into details on what you need to consider when selecting a feedforward capacitor. It discusses the benefits of a feedforward capacitor as well as discusses what can happen with too large of a feedforward capacitor. It also links to additional Application Reports if you would like to know even more.

    www.ti.com/.../sbva042.pdf

    Application specific factors including board layout will impact the stability of a regulator and simulations are often idealized; therefore, we recommend performing load transients while monitoring the output on a scope. By performing the worst case load transients for your specific application, you will be able to check the stability of your application. While this bench test will be most meaningful on your actual application board, the TPS7B4253EVM can be used during initial testing. The following Application Report goes into more detail on how load transients can be used to check stability:

    www.ti.com/.../slva381b.pdf

    Very Respectfully,
    Ryan