m_w has joined ##openfpga
m_w has quit [Quit: leaving]
m_w has joined ##openfpga
talsit has joined ##openfpga
pie__ has quit [Changing host]
pie__ has joined ##openfpga
<azonenberg> pointfree: this seems like something that would be easily solved by looking at the silicon
Lord_Nightmare has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
m_w has quit [Quit: leaving]
Lord_Nightmare has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
kuldeep has quit [Quit: Leaving]
Lord_Nightmare has quit [Ping timeout: 246 seconds]
Lord_Nightmare has joined ##openfpga
<cr1901_modern> azonenberg: What's your rule of thumb for which freqs caps should block? 10 times the maximum speed signal you expect to see?
<cr1901_modern> (when making a PCB)
<azonenberg> cr1901_modern: for what, decoupling?
<azonenberg> bear in mind, discrete caps arent all that effective at decoupling beyond a few hundred MHz
Lord_Nightmare has quit [Ping timeout: 244 seconds]
<azonenberg> the parasitic L dominates at that point
kuldeep has joined ##openfpga
<cr1901_modern> azonenberg: I guess it's decoupling? I mean "filtering out transients and cleaning the power signal"
<azonenberg> yeah
<azonenberg> So, I typically start a bit below the SMPS cycle frequency (anything much lower is going to be handled by the SMPS feedback loop)
<azonenberg> then go up to circa 10x the max clock frequency of the component, but not to exceed ~500 MHz
<azonenberg> sometimes not even
<azonenberg> Most of the time if i have a high-speed part like an FPGA there's a recommended decoupling network in an appnote anyway, so i can get by with using that
<azonenberg> and forget the calculations
<cr1901_modern> Hmmm...
<azonenberg> But if you're over 500 MHz or so for decoupling, the parasitic L adds a few ohms of resistance and your decoupling is no longer really useful
<azonenberg> An ohm or two isnt a big deal for an RF signal, which is why pF range caps exist
<azonenberg> but in an ultra-low-impedance power trace/
<azonenberg> its practically an open circuit :p
<cr1901_modern> I should've taken RF electronics
<cr1901_modern> In any case, this board is powered by USB... it includes two buck regulators tho, so the capacitor network is important
<azonenberg> Input caps - watch inrush or the port may shut you down
<azonenberg> dont go TOO overboard
<azonenberg> or alternatively use an active inrush limitert
<azonenberg> limiter*
<cr1901_modern> Call it version 0.1 then I guess :P
<cr1901_modern> One thing I never really understood... what is the utility of an analog and digital GND plane if both of them must ultimately have the same return path?
<cr1901_modern> I can appreciate that an analog ground might be less noisy than a digital gnd, but I would think if you connect the two, those advantages would be lost
<cr1901_modern> (GND is stupid)
<azonenberg> I *think* the idea is to have a high-impedance connection between them
<azonenberg> such that in the long term they're at essentially the same voltage (and you don't have problems with them drifting apart)
<azonenberg> but high freq noise on one can't cross to the other
<azonenberg> Everything i've done has always had a common ground, though
<azonenberg> and if i wanted to isolate SMPS noise i did it in the power rail only
<azonenberg> you only have to add impedance at one point in the current path
<cr1901_modern> azonenberg: In this case, I have two components that want an analog ground: The FT232H has three (!) pins for AGND, and the PLL on the FPGA requires a not-noisy GND
<cr1901_modern> Everything else is fine being a digital GND
<azonenberg> I tie all the grounds together
<azonenberg> then add a pi filter between Vx and AVx
<cr1901_modern> So you essentially just filter at the high potential terminal instead of GND.
<cr1901_modern> ie Vx => filter => AVx => analog circuitry => GND
<cr1901_modern> And thus it doesn't matter if the voltage/GND fluctuates, the AVx portion won't "see" it thanks to the filter?
<cr1901_modern> Maybe I'll do that
<azonenberg> Yeah
<azonenberg> As long as AVx/gnd doesnt fluctuate i dont care
<azonenberg> now, a local bump in ground due to ground bounce is always possible
<azonenberg> but none of the stuff i've buitl has been sensitive enouhg for that to matter
Neuron1k has quit [Ping timeout: 248 seconds]
<azonenberg> esp given that the pi filter includes a cap to ground that acts to keep AVx/gnd constant
Lord_Nightmare has joined ##openfpga
DocScrutinizer05 has quit [Disconnected by services]
<cr1901_modern> Ground bounce was the scenario I was (poorly) trying to describe
DocScrutinizer05 has joined ##openfpga
<cr1901_modern> I would HOPE that the pi filter would make Vx less noisy ;)
Neuron1k has joined ##openfpga
<cr1901_modern> Tbh, I'm copying parts of the IceStick schematic for this design. I mean, everything I've thrown at my IceStick has worked fine
<cr1901_modern> (including using the PLL up to 240MHz, which is far beyond what I need)
Lord_Nightmare has quit [Ping timeout: 250 seconds]
Lord_Nightmare has joined ##openfpga
flaviusb has joined ##openfpga
azonenberg_work has quit [Quit: Leaving.]
tecepe has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 268 seconds]
pie__ has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
Felix__ has joined ##openfpga
Lord_Nightmare has quit [Excess Flood]
Lord_Nightmare has joined ##openfpga
felix_ has quit [Ping timeout: 244 seconds]
clifford has quit [Ping timeout: 260 seconds]
Lord_Nightmare has quit [Ping timeout: 240 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 245 seconds]
Lord_Nightmare has joined ##openfpga
tecepe has quit [Remote host closed the connection]
Lord_Nightmare has quit [Excess Flood]
Lord_Nightmare has joined ##openfpga
kuldeep has quit [Ping timeout: 268 seconds]
kuldeep has joined ##openfpga
F1nger has joined ##openfpga
<openfpga-github> [yosys] azonenberg pushed 7 new commits to master: https://git.io/v18vX
<openfpga-github> yosys/master 88b9733 Clifford Wolf: Added "yosys-smtbmc --aig"
<openfpga-github> yosys/master 52c243c Clifford Wolf: Added support for partially initialized regs to smt2 back-end
<openfpga-github> yosys/master 5fa1fa1 Clifford Wolf: Added "write_aiger -zinit -symbols -vmap"
massi has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 250 seconds]
kuldeep has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 248 seconds]
kuldeep has joined ##openfpga
kuldeep has quit [Ping timeout: 250 seconds]
kuldeep has joined ##openfpga
lain has quit [Quit: WeeChat 1.6]
bibor has quit [Ping timeout: 244 seconds]
lain has joined ##openfpga
bibor has joined ##openfpga
Lord_Nightmare has joined ##openfpga
marcus_c has quit [Ping timeout: 260 seconds]
marcus_c has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 245 seconds]
Lord_Nightmare has joined ##openfpga
Bike has quit [Quit: halal]
clifford has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 246 seconds]
tecepe has joined ##openfpga
Lord_Nightmare has joined ##openfpga
pie_ has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 250 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 244 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
pie_ has quit [Ping timeout: 265 seconds]
pie_ has joined ##openfpga
maaku has quit [Quit: No Ping reply in 180 seconds.]
maaku has joined ##openfpga
pie_ has quit [Ping timeout: 244 seconds]
Lord_Nightmare has quit [Ping timeout: 258 seconds]
Lord_Nightmare has joined ##openfpga
Felix__ is now known as felix_
Lord_Nightmare has quit [Ping timeout: 265 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 250 seconds]
firebird_ has joined ##openfpga
firebird_ is now known as cosmobird
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 260 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 260 seconds]
pie_ has joined ##openfpga
Lord_Nightmare has joined ##openfpga
tecepe has quit [Remote host closed the connection]
Lord_Nightmare has quit [Ping timeout: 240 seconds]
pie_ has quit [Ping timeout: 244 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 245 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 250 seconds]
tecepe has joined ##openfpga
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 258 seconds]
tecepe has quit [Ping timeout: 256 seconds]
Lord_Nightmare has joined ##openfpga
Lord_Nightmare has quit [Ping timeout: 260 seconds]
pie_ has joined ##openfpga
Lord_Nightmare has joined ##openfpga
tecepe has joined ##openfpga
pie_ has quit [Ping timeout: 260 seconds]
pie_ has joined ##openfpga
maaku has quit [Quit: No Ping reply in 180 seconds.]
maaku has joined ##openfpga
digshadow has quit [Quit: Leaving.]
Bike has joined ##openfpga
F1nger has quit [Quit: Leaving]
amclain has joined ##openfpga
azonenberg_hk has joined ##openfpga
azonenberg_hk has quit [Quit: Leaving.]
tecepe has quit [Ping timeout: 245 seconds]
digshadow has joined ##openfpga
azonenberg_hk has joined ##openfpga
azonenberg_hk has quit [Remote host closed the connection]
tecepe has joined ##openfpga
digshadow has quit [Ping timeout: 256 seconds]
tecepe has quit [Remote host closed the connection]
digshadow has joined ##openfpga
massi has quit [Remote host closed the connection]
digshadow has quit [Quit: Leaving.]
sharebrained_ has joined ##openfpga
sharebrained has quit [*.net *.split]
pointfree has quit [Ping timeout: 268 seconds]
m_w has joined ##openfpga
Lord_Nightmare has quit [Quit: ZNC - http://znc.in]
Lord_Nightmare has joined ##openfpga
azonenberg_hk has joined ##openfpga
azonenberg_hk has quit [Remote host closed the connection]
pointfree has joined ##openfpga
pointfree has quit [Ping timeout: 265 seconds]
pointfree has joined ##openfpga
pointfree has quit [Ping timeout: 250 seconds]
pointfree has joined ##openfpga
pointfree has quit [Ping timeout: 245 seconds]
pointfree has joined ##openfpga
pointfree has quit [Remote host closed the connection]
pointfree has joined ##openfpga
cosmobird has quit [Ping timeout: 245 seconds]
azonenberg_hk has joined ##openfpga
azonenberg_hk has quit [Ping timeout: 260 seconds]
pie_ has quit [Ping timeout: 258 seconds]
pie_ has joined ##openfpga