No. I'm saying you missed the two words I underlined. Up to. As in from something less than UP TO 3V. As shown on the graphs of several DS.neil.johnson wrote: ↑Mon Sep 14, 2020 8:25 amTI LM317: https://www.ti.com/lit/ds/symlink/lm317.pdfI suspect the author meant (and is clear from the rest of that paragraph) that the device requires a minimum 3-V headroom. So you're saying TI are making false statements?8.4.2 Operation With Low Input Voltage
The device requires up to 3-V headroom (VI–VO) to operate in regulation. The device may dropout and OUTPUT voltage will be INPUT voltage minus dropout voltage with less headroom.
ST is speaking about their device, I covered that aready in my reply. I didn't say all DS were the same. In fact, I said the opposite. Suely you already know this as does anyone who lived through the development of TTL and CMOS with all the differences that caught the collective 'us' up unexpectedly. and apparently still do catch some people unexpectedly.ST LM317: https://www.st.com/resource/en/datasheet/lm317.pdf
Figure 3 shows that at 1A load the LM317 requires a voltage differential of 3V (by eye), dropping to around 2.5V at minimum load. So is ST also making false statements?
It shows what you're trying so hard to ignore and save face about. That the device does *not* require a 3V drop.ON: https://www.onsemi.com/pub/Collateral/LM317-D.PDF
Figure 10 shows that for 1A load the dropout voltage is a smidge under 2V at 50'C silicon temperature, rising to just above 2.0V at room temp (less likely scenario once it starts passing current). Nice plot, but what does it really show?
So when they agree with you, they're good examples, like the ST above. But when they don't, you go after them is sideways? "Pay no attention to the man behind the curtain"? These graphs are -according to you now- only a "guide" but the spec which has *no* minimum value -only showing a *test* voltage, is gospel enough fo ryou to keep figthing for your false belief? Test voltage spec which is of course common in DS -and often supported by plots-graphs. They need to let us know the parameters around which their testing was done. Can't you just admit you were -at least partially- wrong?Fairchild: https://neurophysics.ucsd.edu/lab/LM317.pdf
Figure 3 shows that, again for 1A load, you need a minimum headroom of around 2.3V. At full rated current it is more like 2.5V, but these graphs are rather a guide than law (how many devices did they test? across how many batches? what's the distribution? etc)
Yes,. That's what I said. But then the ones which *do* go further SHOW that 3V is *not* a minimum. Again, I would think with all your expertise you'd be familiar with copied and selectively edited and shortened 'shared' DS. Bob Pease and Jim Williams cautioned us about that over and over again. Closer to the synth world so did Serge and many others in early Electronotes. Especially WRT Norton amps and OTAs DS.In almost all of these datasheets the test conditions in the Electrical Characteristics tables quote the Vo-Vi as between 3V and 40V.
That's a whole lot of words which *are* mostlyv -if not fully- true but which have NO BEARING ON THE PRESENT DISCUSSION. Because the DS in the present discussion DO NOT limit themselves to 3V. Maybe ST does. i didn't read it. Taking your word for that one. The DS in THIS discussion give graphs which show that the dropout is variable and show us how the various parameters we'd be concerned about change with different choices we'd make. Like I already said. And you just repeated above. The problem -for your argument- is your words "if you step outside of that range" do. not. apply. Because 3V is not an absolute minimum value for the device.What that is saying is that these are the ranges of operation that the device is guaranteed to perform over. If you step outside of that range then you're on your own. And what that means is: it may work for you, it may also work for your best buddy, but if you go into production with a circuit that operates outside of those parameters and you start having products fail due to marginal parts, if you then go crying to the manufacturer of the particular LM317 (or whatever) part you are using the Apps Engineer will simply point out you violated the rules so the parts are behaving as advertised and you're on your own. Or, if you were sensible and involved the Apps Engineer in your design before going into production they would simply request you increase the input voltage or change your design (e.g., LDO regulator).
I forget what kind of false argument your words above are called? Straw dog? Red herring? No. But there's a name for that kind of wordy truth spoken as if it applies.. misdirection?And by production, I also mean releasing a board for other DIYers to make. They will buy or make the board, they will buy the parts, they will spend time putting it all together.
I'll vouch for the single module design. Probably the larger one too. But it 'might' be well to put a note for maximum draw on that one. Again you've given nothing but more more 'sideways' words to put us off the fact that your first statement is more often than not as false as I said it was -accounting for the ST DS which according to your report does agree with your initial assertion.
it's funny to me that it's ST, as I've had more problems with that brand -along this exact type of difference- over the decades than any other. They always seem to be just a little different than nearly everyone else. Of course that's TOTALLY anecdotal, and may only apply to my personal experience. But since it does, it's funny to me that it's ST. When they were still SGS Thomson I didn't have the same experience as after they became ST. *I too can use a lot of words that don't really apply to the discussion at hand!" And a search here and Electro-music will show mumerous examples of ST devices not working in certain synth circuits. Of course that's also true for some other mfrs.
Harald doesn't need 'luck'. From what I've observed -over several years now- Harald is a careful and gracious provider of well-engineered, robust and useful modules. Moreso than many you could choose to go after the way you did this design.But, heh, good luck to the OP, looks like he's having fun.
That's probably a good idea.I'm signing off, have too many projects needing attention as it is