[SOLVED] How far from the device can I place my bulk capacitor?

[lizsagzki]

If I have a propagation delay of 150ps/inch, where should I place my bulk capacitor (with respect to the device) that has a resonant frequency of 6MHz?

 

[malli_1729]

If we calculate wavelength of the capacitor's resonant frequency it is close to 1111 inches. There are different thumb rules like 0.005*Lamda or 0.1*lamda......
But this is not depending up on just capacitor's properties....IT depends on How it is connected to the circuit(Channel connected between Load and Decoupling capacitor and it's effectiveness), what is stack up etc.
It involves lots of equations as mentioned in
http://www.sigrity.com/papers/epep2001/web_decouplingRadius_final.pdf

Generally Bulk capacitors will be used either for filling lower value capacitor's(0.01uf,0.1uf..etc) charge during non-Transition period or to respond to big low frequency transients.
generally 1 or 2 inches from surrounding Chip is good estimate.

I recommend to follow manufacturer's recommendations.
refer
http://www.freelists.org/post/si-list/Effective-Radius-of-Decoupling-Capacitor
http://www.sigrity.com/papers/epep2001/web_decouplingRadius_final.pdf