#avr Logs

May 06 2022

08:33 AM specing_ is now known as specing
09:02 AM LeoNerd: So. I need a programmable output voltage for a logic signal. The signal will come from probably a 74LVC1G125, which I can power from anything from 1.2V to 5V. I have a choice on how to get that voltage
09:03 AM LeoNerd: The usual choices are external DAC, or PWM to generate the voltage then opamp. But given that even something simple and cheap like the MCP4725 can source 25mA, it's probably looking like the easiest choice. I'm already using a lot of I²C for my other peripherals anyway, so I get that for free.
09:04 AM LeoNerd: Even the simplest PWM-DAC output would need an opamp to buffer the voltage, and that opamp is probably at least a SOT-25-5, which is about the size/cost of the MCP4725 anyway. So.. probably just that? Unless anyone has any other ideas
09:04 AM LeoNerd: The tiny1616's own DAC module doesn't go up to VCC so I can't do 5V output, and anyway I need two separate ones so that's no good
09:15 AM rue_mohr: did you see what they did with the TL866?
09:17 AM LeoNerd: Oooh no?
09:18 AM rue_mohr: are you doing a chip programmer?
09:18 AM LeoNerd: No
09:18 AM rue_mohr: or chip tester?
09:18 AM rue_mohr: or bench equip?
09:19 AM LeoNerd: bench stuff
09:19 AM rue_mohr: hmm
09:20 AM LeoNerd: A little programmable clock-rate generator. It's basically just the Si5351 in a box
09:20 AM rue_mohr: yup
09:20 AM LeoNerd: A bit of a display and control interface.. also some switchable voltage output
09:20 AM rue_mohr: mine only does 5V out
09:21 AM LeoNerd: I think I'd have enough need for 3.3V also, that making it switchable is good. At which point, a DAC for anything is quite easy
09:21 AM rue_mohr: but I go 10MHz - 0.01Hz
09:21 AM LeoNerd: Getting the Si5351 down that low is tricky.. it's not really made for lower frequencies
09:21 AM rue_mohr: I used an array of 7490
09:22 AM rue_mohr: the DDS runs 1MHz - 10MHz, and its picked off depending on the range
09:22 AM rue_mohr: http://ruemohr.org/~ircjunk/projects/freqGen/slide.htm
09:23 AM rue_mohr: I had a hell of a time trying to make an osc that went from 1-10MHz, gave up
09:23 AM LeoNerd: The Si is a good chip for that
09:23 AM rue_mohr: when I got there, it wasn't stable
09:27 AM rue_mohr: I learned that, for a normal oscillator 10:1 is insane
09:30 AM rue_mohr: huh, I have that state machine now...
09:31 AM rue_mohr: but I got a chineese one and it can do variable duty
09:31 AM rue_mohr: .... and sine waves
04:52 PM LeoNerd: Ugh. Trying to buy ICs currently. Half the things I want are out of stock at Mouser, expected sometime in 2023
04:52 PM LeoNerd: One here even expected 29th May, ... 2023. That's OVER A YEAR AWAY
04:53 PM exp: ah yes, microchip parts?
04:53 PM exp: basically everything of theirs is like this
04:53 PM exp: LeoNerd: hwat do you need?
04:53 PM LeoNerd: 74-series logic gates. little tiny SOT-23-5-sized ones
04:53 PM LeoNerd: 74LVC1G125
04:54 PM exp: oh yes, i have an 6 xor gate backorder that keeps getting pushed back
04:54 PM exp: but there's still dozens of others available
04:54 PM exp: although maybe that's down to singles now
04:54 PM LeoNerd: Hah! That exact part number on Mouser: 41 results. Filter by "normally stocked", 34. Filter by "actually in stock right now" - only 5
04:55 PM exp: Mfg Part Number: NC7SV86P5X
04:55 PM exp: Revised Delivery Date*
04:55 PM exp: 02/27/2023
04:55 PM LeoNerd: Mmm.. The only ones they actually have are this absolutely microscopically-sized XSON-6 package
04:56 PM exp: do you really need ttl logics?
04:56 PM exp: do you have tight level requirements?
04:56 PM LeoNerd: I need something LVC... I'm using it as a 3.3 -> (anywhere from 1.2 to 5V) level shifter
04:58 PM exp: surprised if there's nothing available at all
05:00 PM LeoNerd: I wonder if I can find/get/make an XSON-6 breakout board
05:00 PM exp: oof 0.35mm pitch
05:00 PM exp: that is expensively tight
05:00 PM exp: use a cheap fabricator that won't check their lithography properly lol
05:01 PM LeoNerd: It is teeeeenytiny
05:01 PM exp: yes i have one part this fine and my tech HATES it
05:38 PM LeoNerd: OK, well I think I can make a breakout board for this, but it's almost all pin header. :P The chips are so small in comparison
06:16 PM qu1j0t3: LeoNerd: i'm planning to use these for level shifting https://www.digikey.ca/short/4r8czn2d
06:44 PM qu1j0t3: oh lol out of stock and i didn't even notice ._.
06:45 PM qu1j0t3: i did buy some before the end but not enough to retire on
06:52 PM qu1j0t3: tht that is. there is smd in stock
06:52 PM qu1j0t3: 14soic
07:25 PM rue_mohr: you ALWAYS have to check the in-stock box
07:32 PM qu1j0t3: yes.
07:32 PM qu1j0t3: i do.
07:32 PM qu1j0t3: except this time. in any case there are over 7K of this nice level shifter in SMD
08:33 PM specing_ is now known as specing