Hello everybody i am trying to set the frequency of a 3525 with this formula 1/(1,10^-9*(0,7*15000+3*22))=94643HZ
where ct =µf
rt=ohms
my results=-1,05!
thank you for helping me!

 

Your number is close to -1 so there must be at least 2 problems. Should be positive and should be a large number.
"^-9" I think you are not doing that right. 1.10^-9 is a very small number.
Where did you find the formula? What is a 3525?

 

What is a 3525?

I'm assuming it is a SG3525. https://www.st.com/en/power-management/sg3525.html

 

I get 94.643Khz.

15000* 0.7= 10500
+66 = 10566
* 1exp-9 = 1.05exp-5
1/ 1.05exp-5 = 94643..

 

ronsimpson: yes a SG3525!

 

hello dodgydave and thankyou for this formula!
best regards

 

this formula 1/(1,10^-9*(0,7*15000+3*22))=94643HZ

That's not a formula, its a numerical expression. I get 86039Hz if you take 1.1E-9 for the first element in bold, though I can see it could be misread as 1 x 10E-9.. What was your value for \(C_t\)?

The formula is:
\(f(Hz) = 1/C_t (0.7R_t + 3R_d)\), where \(R_t\) and \(R_d\)are in ohms and \(C_t\) in F

With \(R_t\) and \(R_d\) in ohms and \(C_t\) in uF the result is in MHz

 

Hello irving sorry i am late! the value for ct is 1NF
so: 1/0,001*(0.7*15000+3*22)=105660

 

No, you must get the top & bottom right, its:

\(f(MHz)=1/C_t(0.7R_t+3R_d)\), where \(R_t\) and \(R_d\) are in ohms and \(C_t\) in uF NOT

\(f(MHz) = 1/C_t . (0.7R_t + 3R_d)\)

f = 1/( 0.001 * (0.7 * 15000 + 3 * 22)) = 0.0946431MHz = 94.64kHz

NOT

f = 1/(0.001) * (0.7*15000 + 3 * 22) = 10566000 ???

 

hello irving ok ! thank you
best regards!