I can use your help.

I need a high precision capacitor to implement the RC match filter across an inductor to measure the current through it.

enter image description here
Picture taken from (IC is not relevant in this question): http://www.ti.com/product/LM27403/datasheet/detailed_description

You can imagine that the capacitor needs to be very precise in order to effectively match the L/DCR of the inductor to the R*C time constant.

What I'm asking is, can you recommend any material or type of capacitor that I can use the best. [Deleted own requirements, question will be obsolete for others] I know that this technique is not rock solid because of environmental influences, that why a high precision capacitor here is mandatory.

Thanks for your time and support :)

  • \$\begingroup\$ The datasheet doesn't say it has to be precise, and it's not a match filter; it just says "Choose the capacitance of CS greater than 0.1 µF". Capacitor precision is not easy to achieve, anyway. \$\endgroup\$ – pjc50 Oct 14 '15 at 9:01
  • \$\begingroup\$ Indeed, Cs is only there to suppress the (switching) noise that is present on the voltage across the inductor. No need for it to be accurate, you can use any capacitor larger than 100 nF. \$\endgroup\$ – Bimpelrekkie Oct 14 '15 at 9:14
  • \$\begingroup\$ Sorry to give the wrong idea. The link is to indicate that it is not a picture of my own making. It has nothing to do with the IC on that specific page. (I will edit it) Anyway thanks for your support. \$\endgroup\$ – Weaverworm Oct 14 '15 at 9:14
  • \$\begingroup\$ So the circuit isn't your actual circuit? Am I understanding this incredible fact correctly? \$\endgroup\$ – Andy aka Oct 14 '15 at 10:07
  • \$\begingroup\$ No you do not. This ís my circuit. Exactly like this (buck converter). I just don't use the IC which they mention at the site of Texas Instruments. \$\endgroup\$ – Weaverworm Oct 14 '15 at 10:14

Use an NP0 ceramic capacitor for good precision at a reasonable price.

For example, a C0805C223F5GACTU 22nF 1% is about $2 usd in 100's and if you can live with 2% there is a Murata part that is about $0.35 ea.

  • \$\begingroup\$ See, this is an answer I can work with. Thanks a lot! \$\endgroup\$ – Weaverworm Oct 14 '15 at 10:24

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