Werner Almesberger wrote: > Rene Harder wrote: > >> My main idea of using discrete filters though, was to keep new >> components (with different packages) as small as possible to reduce SMT >> assembly cost. >> > > Yes, I was hoping that we could have one "universal" filter that's > suitable for all low-frequency signals (audio, UART, etc.), given > that most of the noise lives >> 100 MHz and those low-frequency > signals are << 100 MHz. > > >> Also you are more flexible with a discrete filter than with a single >> component one; If we mess things up, we can just replace the caps or the >> inductor and fix the problem but with a single component filter we would >> need a different one and might need to change the pcb pattern as well. >> > > That's true, yes. Of course, I fervently hope that we can avoid the > joy of precision-tuning those filters ;-) > > >> However, I think we are better off using a single component filter, this >> decreases complexity and risk of possible misbehavior. >> > > Great ! > > When we discussed integrated filters, we came up with the following > components: > > Murata NFL18ST (0603, "T"): > http://search.murata.co.jp/Ceramy/image/img/PDF/ENG/L0112S0119NFL18ST.pdf > > Rohm MCF182CN102 (0603, "for power supply"): > http://www.rohm.com/products/databook/emi/pdf/mcf18.pdf > > TDK MEM2012P101R (0805, "Pi"): > http://www.tdk.co.jp/tefe02/e9617_mem_p.pdf > > Which one would be closest to the kind of "universal" filter we're > looking for ? As usual, smaller would be better :-) > >
I'm still in favor of the pi-filter but let me do another search. Maybe I'll find a smaller one with similar characteristics ;-) >> I've no idea what the purpose of this resistor is/was. This seems to be >> an ordinary pull-down resistor but for what I can't tell for sure. >> Nothing makes completely sense to me. >> > > Are we talking about the same part ? R4401 is 220 Ohm and series, while > the pull-downs in the area (R4416, R4117) are 10 k. Looks more like a > current-limiter for problem conditions to me. > > Ups my bad. Unfortunately, I mixed up R4401 with R4404! Yes this one looks pretty much like a current limiter. _______________________________________________ gta02-core mailing list [email protected] https://lists.openmoko.org/mailman/listinfo/gta02-core
