peak to peak voltage ripples

[DimaKilani]

I designed a switched capacitor and i need to measure the voltage ripples. I assume that the Vripple=5%Vout_avg.

when i simulate the circuit, i consider Vripples as peak to peak output voltage that is: Vripple= Vout_max - Vout_min. Should not i have to divide by 2 because am taking the peak to peak ?

Thanks

 

[KlausST]

Hi,

Peak to peak means: The complete value of the max_voltage_peak - min_voltage_peak.
Don' t divide by 2

Klaus

 

[D.A.(Tony)Stewart]

Peak ripple would of course be (Max-min)/2 which is closer to rms noise, but depends on if your interest is thermal noise, clock feedthru or some other noise in the signal. Normally if it is fundamental f or 2f , we call it ripple, otherwise just "noise p-p" covers all types including transient noise.

https://www.seas.ucla.edu/brweb/teaching/AIC_Ch12.pdf

 

[crutschow]

What do you mean by "Vripple=5%Vout_avg"? Is that the maximum ripple you want?
Whether you need to divide the pk-pk value by 2 or not depends upon the definition of Vripple.

 

[DimaKilani]

For example, I have an output voltage that has ripples so I took the average Vavg. and then I assume that the expected Vripple= 5%Vavg. This means that Vout= Vavg+Vripple or Vout= Vavg-Vripple ? Does that true ? Then Vripple= V_max-Vmin/2 .. what do you think ?

 

[KlausST]

Hi,

its a problem of definitions.:

ripple can be seen as AC. With AC you usually talk of RMS voltage. The average of a ripple should be near zero.
But how RMS and peak voltage of a "undefined" ripple is nobody can tell. Peak/RMS can be 0.5 or it can be 0.05 or inbetween or even worse....

With a pure sine the RMS value is 0.707 of the peak, but the average of the sine is zero.

With a pure DC signal then RMS = peak = average.

I know it is all that complicated.....


Hope this helps.

Klaus