Whats wrong with this ADG1633 SPDT analog SW in LTSpice ? - Page 1
Forum section: electronics / projects

author: MathWizard
author_rank: Super Contributor
timestamp: August 08, 2020, 10:05:12 am
content: [ Specified attachment is not available ]I'm using the ADG1633 SPDT analog sw (under ) which is the most similar thing to a CD4053 I can find in LTSpice. IDK if the ADG came with LTS or not, I have extras.https://www.analog.com/media/en/technical-documentation/data-sheets/ADG1633_1634.pdfhttps://www.ti.com/lit/ds/symlink/cd4051b.pdf?ts=1596836124263&ref_url=https%253A%252F%252Fwww.google.com%252FThe test fixture of the part works, but when I put it in a schematic, I'm getting uA of leakage current from the side that supposed to be off. Even if I ground the toggle control, and just run DCopp, I still get 5V/1Meg=5uA. But it's supposed to be off, and only have nA or pA of leakage, like in the test fixture.The test fixture is on the left w/ waveformThe right side is an example circuit just at DC, the 1k is suposed to be on, and has 5mA , but the 1Meg has 5uA, and giving 5V over it. Stepping that R gives a JFET type roll off current. Starting at 135uA w/ 10k, and down to 10uA w/ 500k and 5uA w/1Meg. And changing Vss=-9V to GND did nothing either.But again the built in ADG1633 test works as it should, with only pA of leakage.Notice the extra GND on the ADG in the test, by Vss, adding it does nothing, there's no connectino box there either.

author: Ian.M
author_rank: Super Contributor
timestamp: August 08, 2020, 11:28:36 am
content: Locate the ADG1633 subcircuit in lib\sub\ADG.lib, and study its netlist. Trace back from node 2 (aka: SA or your Ay) to figure out where the pin voltage is coming from. You can plot internal node voltages and part currents from the subcircuit by 'Add Trace' in the plot window - refer to the SPICE Error Log to map them back to the subcircuit.If that doesn't help, you can reverse engineer the subcircuit as a hierarchical schematic from its netlist by adding the parts one at a time in netlist order to a new schematic called myADG1633.asc, labelling each new node you encounter. After each part has been added, check the resulting netlist matches the subcircuit. Finally, create a new instance of the symbol (as myADG1633.asy) in your working directory, flip its type from 'Cell' to 'Block' and strip *all* attributes, then rename the pin nodes in your myADG1633.asc sub-schematic to the pin names defined in the new symbol.However, I think your time would be better spent finding an actual 4053 SPICE model, porting it to LTspice and constructing a symbol for it.

author: MathWizard
author_rank: Super Contributor
timestamp: August 08, 2020, 06:53:15 pm
content: Alright thanks I'll have to try that, but I've never worked on that side of the models before.I downloaded some guys list of extras parts, under a folder called ZZZ in the component list. There's a symbol in there for a full and 1/3 of the 3x SPDT 4053. But so far it seems devoid of the required info. And I found a LinearT/Analog Devices site that might help fill in some of that info.It's not critical for my circuit to use these, I could make a FET sw or try some other SW's even if I used 2.

author: MathWizard
author_rank: Super Contributor
timestamp: August 09, 2020, 11:52:56 am
content: Ok it's the Common in/out thats leaking into the S1B (Ay). I can see the 5uA from 1 to the other, and the few nA from the Vdd is there too.I've made it a fair way into the subcircuit, just learning what it all means. It uses some mosfets like.model N VDMOS(Kp=.12 Vto= .5 Is=0 mtriode=1.3 Cgs=10p Ksubthres=.4 nlev=3 gdsnoi=2).model P VDMOS(Kp=.12 Vto=-.5 pchan Is=0 mtriode=1.3 Cgs=10p Ksubthres=.4 nlev=3 gdsnoi=2)So I'm making a model that looks like a 16pin stack/ladder of lines(nodes). If the m=.22 is supposed to be Rdson, I've picked a 30V mosfet to try just to compare.I guess tho I can cut line by line from the subckt file too.I make it that far and go to make a mosfet like they use but my hotkeys don't work, so I can't start a new line in the .op box with Crtl+M. So for now I suppose I'll try with notepad.I like this kind of stuff, LTSpice and I will have a long future.

author: Ian.M
author_rank: Super Contributor
timestamp: August 09, 2020, 12:28:22 pm
content: Do you mean your Ctrl key doesn't work? What OS is your PC running?(I assume some flavour of Windows from 'Notepad'.)The Ctrl key is pretty much essential for LTspice as in the schematic window you need it to access the generic Component Attribute Editor rather than the device specific wizards. You can workaround it not being available for RMS and average measurements in the plot window,by carefully crafted .measure scripts, and in the schematic Text dialog get new lines by pasting from a real text editor, but its a PITA to have to do so. You could try the Accessibility tool: On-Screen Keyboard to let you key  when required. Alternatively plug in a fully working keyboard!