Path: ...!news-out.netnews.com!postmaster.netnews.com!eu1.netnews.com!not-for-mail X-Trace: DXC=oA:JOYU];Hf:iCDmkJ2@IdU5[F2hIijDo7J470dMQQ7kIW^IYg9S>^h Content-Language: en-US From: bitrex In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Lines: 36 Message-ID: <672297c3$1$18$882e4bbb@reader.netnews.com> NNTP-Posting-Host: 127.0.0.1 X-Trace: 1730320323 reader.netnews.com 18 127.0.0.1:46879 Bytes: 2264 On 10/30/2024 4:07 PM, john larkin wrote: > Things I've seen, and even done, in Spice sims... > > Bypassing voltage sources (not me!) > > Worrying about resistor power dissipation > > Using standard parts values, like 4.7K ohms or 33nF, when the control > loop will be mostly code anyhow > > Using +-12 or some such opamp supply voltages, and scaling signal > levels to fit. The LT Spice universal opamps will work with hundreds, > or thousands, of volt supplies. > > Drawing hideously ugly schematics without a title, author, date, or > named nodes. > > > So I'm rescaling a power supply sim (I'm waiting for a run to finish > now) to have everything in actual 1:1 units. Then we will write the > control loop code to work in those same real engineering units, not > some goofy scaled integers or anything like that. > > Keeping everything in true units as floats is ideal, but the RP2040 > floating point ops are kinda slow, so we may express things as 32-bit > values, 16 bits of signed integer and 16 bits of fraction, as a sort > of fast and cheap float. But 12.5 volts is still visibly 12.5, just > as if it were a float. That will be handy for debugging. > > S16.16 is plenty good to express voltages and currents in a power > supply. > Floating point sucks for low frequency systems with relatively long time constants, anyway