what circuit it this? is it a LC filter?

[nathan80]

The following circuit is a 3.3V filter circuit provided by my PCB maker. I have been using this circuit in the evaluation boards for my analogue IC. the 3.3V is supplied with a programmable digital power supply which does not have much ripple. my chip is supposed to run with high frequency (around 3.125Gbps).

1st of all what filter circuit is this? c18, N1 and c19 together form a 1st order LC filter. i cant seem to figure out what is the function of c20. 1) can some one tell me wat is c20's function?

Do you guys think, I can simpify the following circuit by removing c18. cause if it is a LC filter then the C18 functions to filter the high frequency noise since my power supply produces voltage with less ripple.

anyone have any other sample filter circuits to share?


thank you in advanced

 

[Wenye]

Hi Nathan,

It just a de-coupling circuit for your power supply. To provid more clearly power for your analog IC.


Best Regards,
Wenye

 

[Kral]

nathan80,
C19 is a large value capacitor, probably an aluminum electrolytic or tantalum. These capacitors provide large capacitance in a small case. However, the ESR (equivalent Series Resistance) of these capacitor types is relatively high at high frequencies. C20, which is connected in parallel with C19, provides low ESR ast high frequencies.
Regards,
Kral