Hi people. I'm working with an FPGA and some other logic all in leaded packages. I was thinking about how can I provide a good decoupling, but I found myself with some existential thoughts. The first point I came with is that I can't decouple de PS beyond the limitations imposed by the lead inductance. I went to some IBIS models for the QFP and the inductance is about 10nH. Now, counting with 12 VCC pins then I may have an average 1nH inductance. So I thought how much effort I should put in thinking how to decouple this device if the voltage drop is already heavily affected by this inductance. At this point, I don't know if the device has embedded decoupling capacitors in the package, so I assume it doesn't. The manufacturer recommends to just estimate the required capacitance according to the power dissipated by the device, but he never considers the voltage drop due to the inherent inductance during the current spikes at the clock's edges. For low frequencies I assume the approach is correct since the inductance can be neglected. But what about for 150MHz frequencies and above? Or, maybe these packages aren't designed for such high frequencies, in which case I would have to move to BGA or smaller. And what about with the logic in TSSOPs and alike that has similar inductances (even lower) per pin? What I would like you to tell me is how much should I worry for decoupling such devices, and if for ~150MHz frequencies I definitely can't use QFP and TSSOPs. Any further recommendation is welcome. Thanks. geoffrey ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu