I try to calculate R11& R7 by equation(24) & (25), but can't get right value in figure-9.
Please help, thank you.
Hi Jason,
I think I have derived the correct equation, but it does not result in the 46.4k R11 value that they have shown. I have reached out to the original designers but there is no promise that we'll hear back from them. I'll post my equation here:
This results in an R11 value of 37.7k. The equation for R7 will be the same, but I do not calculate the same value they have shown due to the different R11 value. In the case that I do hear back from the designers I will update you here.
Please let me know if you need any further assistance!
Best,
Katlynne Jones
Hi Katlynne,
Thank for your answer, but I still can't have the same value as yours. Here are my parameters and results of R11 & R7.
Could you help to check it, thank you!
Hi Jason,
You are using a Vref of 1.2V. Per section 4.2.2, the Vref voltage from the TPS54040A is 0.8V:
That is the value I used to calculate the 37.7k. You can use a different reference but the resistors will change in order stay within the max and min Vout voltage that you want.
Best,
Katlynne Jones
