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Hi, I am designing a Step-up Booster based on LT1680, for some reasons:
1)Suitable for high power;
2)Through hole package;
3)Simple external architecture.
However, there is a discrepancy between the Datasheet and the LTspice component.
It seems there is a mistake with the LTspice file that has only 14 pins while the real component has 16 and some pin names in LTspice are called differently.
Can anyone please help me?
Thanks
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You may get help here, but you should report
your problem the ADI's Engineer Zone, because the different pin
numbers is clearly ADI's problem.
On 2025-05-19 21:49, Pietro via
groups.io wrote:
Hi, I am designing a Step-up Booster based on LT1680, for
some reasons:
1)Suitable for high power;
2)Through hole package;
3)Simple external architecture.
However, there is a discrepancy between the Datasheet and the
LTspice component.
It seems there is a mistake with the LTspice file that has only
14 pins while the real component has 16 and some pin names in
LTspice are called differently.
Can anyone please help me?
Thanks
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
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I have not looked at yet - but it is very common for SPICE models to have fewer pins than actual pins.? Also, pin names often vary.
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Andy
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Se vuoi dare un'occhiata, ho caricato un file immagine nella sezione foto.
Ok, va bene, ma poi, quando dovrò progettare e costruire il tutto, come collegherò i pin mancanti?
E ??poi, funzionerà correttamente?
Questi sono i miei dubbi.
?
[Mod note:? Please use only English in this group.? A translation to English is below:]
?
If you want to take a look, I uploaded an image file in the photo section.
Okay, that's fine, but then, when I have to design and build it all, how will I connect the missing pins?
And then, will it work properly?
These are my doubts.
?
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That is OK for simulation: commoned pins and
NC pins can be left of the symbol and model, but it is a problem
when passing data to a PC layout app.
On 2025-05-19 21:59, Andy I via
groups.io wrote:
I have not looked at yet - but it is very common for SPICE
models to have fewer pins than actual pins.? Also, pin names
often vary.
?
Andy
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
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Sorry, but please use English only in this group.
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FYI, many op-amp's have Balance adjustment pins, but most of their SPICE models omit them.? Most circuits that used them did not connect to those pins anyway.
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Andy
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LTspice is not meant for circuit layout.? When it is used for that, it MUST be assumed that "touch-up" is probably needed.
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Andy
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Your upload is helpful, but you must post in
English. Google Translate is your friend.
On 2025-05-19 22:04, Pietro via
groups.io wrote:
Se vuoi dare un'occhiata,
ho caricato un file immagine nella sezione foto.
Ok, va bene, ma poi, quando
dovrò progettare e costruire il tutto, come collegherò i pin
mancanti?
E ??poi, funzionerà
correttamente?
Questi sono i miei dubbi.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Sì, scusa. Mi sono confuso.
?
[Translation to English by Moderator:]
?
Yes, sorry. I got confused.
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Lunedì 19 maggio 2025 alle 23:12, John Woodgate ha scritto:
If you want to take a look, I uploaded an image file in the photo section.
Okay, that's fine, but then, when I have to design and build it all, how will I connect the missing pins?
And then, will it work properly?
These are my doubts.
|
On Mon, May 19, 2025 at 05:28 PM, Pietro wrote:
Okay, that's fine, but then, when I have to design and build it all, how will I connect the missing pins?
And then, will it work properly?
These are my doubts.
Who is the design engineer?? If that is you, then you must be the master of your design.? You need to take full responsibility for understanding what the circuit does and how every part of it works.
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If you seriously don't know what to do with the extra two pins because you couldn't include them in your LTspice simulation, then it is your job to understand how those two pins work, and how they should be connected, and whether they can be ignored by not connecting to them.? Chances are they can't be ignored, and probably should be connected to something.
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When I compared the datasheet with the LTspice symbol, the only two pins I could not match up with the symbol were:
- Pin 8 = Vref
- Pin 15 = SYNC
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Now here is where your engineering skills become important.? What do those two pins do?? What does the datasheet say about them?? In one figure in the datasheet it shows one pin connected to ground, and the other pin connected to a bypass capacitor.? But it is your job to read the datasheet and understand what is the right thing to do with those two pins.
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Most datasheets from Analog Devices have fairly detailed about what every pin does, and how to use it.? Read the datasheet to find out.
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Did you have questions about the naming differences with any of the other pins?
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Andy
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Oops, my reply was sent prematurely.? I started writing:
Did you have questions about the naming differences with any of the other pins?
I concluded that "Iavg" and "Iave" were probably the same, and that "Vfb" and "FB" are probably the same.? But again, it is your job to understand what each of those pins actually does and how to use them.? That should make it obvious which pin is which.
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Are there other pin names you found confusing?
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Andy
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Andy I
I studied the datasheet, I know that it is my final responsibility to make design choices according to my skills, but I believe that the community serves the purpose of sharing problems and solutions and maybe this problem has already been solved by some other member since it is a component from the year 2004 (21 years).
I am writing this post not because I do not know how to connect the 2 missing pins but because I have doubts that the component in LTspice LT1680 is wrong and maybe there is a valid file to replace in the simulation.
(As often happens).
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I mentioned this already, but I think it is worth a bit more elaboration.??John Woodgate wrote:
... but it is a problem when passing data to a PC layout app.
SPICE/LTspice simulations are never meant to constitute the full and complete design database for a circuit layout.? Yes, you can take a schematic in LTspice and export it to a file that can be read by a PC layout program, and that's fine.? But you should ALWAYS assume that the LTspice-generated netlist does not have some things that are necessary for the physical layout, because they were not needed to simulate the circuit.? It should ALWAYS be assumed that modifications and touch-ups will be needed, after the circuit is ported into a PCB layout system.? Anyone who takes an LTspice simulation, exports it to a layout program, and blindly uses it that way is "shooting themselves in the foot".
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The SPICE models for many ICs are not 100% complete and do not include some physical pins.? Some LTspice models omit pins and the functions that connect to those pins, because almost no design engineer ever needs to simulate those parts of the circuit.? So they are omitted from the LTspice model and from the LTspice simulation.? But the real IC has them, and you may need to do something with those pins in the physical design even though they were not a part of the simulation.
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On Mon, May 19, 2025 at 06:02 PM, Pietro wrote:
I am writing this post not because I do not know how to connect the 2 missing pins but because I have doubts that the component in LTspice LT1680 is wrong and maybe there is a valid file to replace in the simulation.
I am not employed by Analog Devices, but I can say with high confidence that the LTspice LT1680 model is correct and it simply did not include those two pins because they aren't needed in the simulations.
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Vref is an internally generated DC voltage that needs a bypass capacitor connected to it, so it has a pin where you can connect one.? You won't use it for anything else, and the SPICE simulation doesn't need it.
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I do not know much about the SYNC pin, except that it seems to be optional, and they recommend grounding it if it is not used.? From the signal name, I am guessing it may have something to do with synchronizing multiple LT1680 parts together.? If you are doing that, then make sure to read the datasheet carefully.? My guess is that they did not include it in the SPICE model because it is rarely ever used, and it likely won't affect the simulation of your DC voltages.
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It is not unusual for SPICE models to omit pins that are rarely used.? I guess this is the first time you saw that.
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Andy
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Pietro
John Woodgate