SPICE - low-side drivers

Thread Starter

Ian0

Joined Aug 7, 2020
4,092
Does anyone have LTSPICE models for low-side MOSFET drivers? Especially those from Microchip?
I found a few in @Bordodynov ’s selection, but SPICE just runs until a week next Tuesday without producing a result. (A lot of “fill ins”, whatever they may be)
Or am I just using them wrongly? Do I have to fill in some other parameters?
 

Papabravo

Joined Feb 24, 2006
17,570
Does anyone have LTSPICE models for low-side MOSFET drivers? Especially those from Microchip?
I found a few in @Bordodynov ’s selection, but SPICE just runs until a week next Tuesday without producing a result. (A lot of “fill ins”, whatever they may be)
Or am I just using them wrongly? Do I have to fill in some other parameters?
It is true that some models have undesireable behavior when trying to do simulations. It is well known that you can construct highly efficient behavioral models to test out circuit concepts. If your goal is to identify parts that you might want to use in an actual design, then you are dependent on the manufacturer to provide what you need. There are many reasons why they might not be interested in doing so, and I'm curious about your experience with Microchip in this regard.

EDIT: Looking at a Microchip datasheet it should be possible to create something from the functional block diagram. Of course after doing so you would need to correlate the behavior of the model with the actual part. I have no idea about your level of tolerance for such an activity.

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Thread Starter

Ian0

Joined Aug 7, 2020
4,092
In the dim and distant past, before iPads existed (because that’s where I keep handy datasheets and application notes these days) Microchip took over Micrel, and reduced the prices on MOSFET gate drivers. They published an application note, which I can no longer find, about using the input hysteresis on some of their low-side drivers to make 555-like oscillators. I made several examples, and with a bit of ingenuity it is possible to make all sorts of switched-mode circuits and square-wave drivers with serious amounts of output.
I had a similar idea I think will work, but I fancied trying it in SPICE first, but no SPICE model.. . . .
I know it’s not a figment of my imagination, because I have one of the circuits in front of me (an LED driver) made about 7 years ago.
 

Papabravo

Joined Feb 24, 2006
17,570
Apparently if you google "Micrel Application Notes" some of them still come up on the Microchip site. Do you have any kind of a helpful handle on the title or a part number?
 

eetech00

Joined Jun 8, 2013
2,807
Does anyone have LTSPICE models for low-side MOSFET drivers? Especially those from Microchip?
I found a few in @Bordodynov ’s selection, but SPICE just runs until a week next Tuesday without producing a result. (A lot of “fill ins”, whatever they may be)
Or am I just using them wrongly? Do I have to fill in some other parameters?
Do you have a specific driver in mind?
 

Thread Starter

Ian0

Joined Aug 7, 2020
4,092
Found the application note (after downloading a dozen and reading through them). Now safely stored on the iPad!
https://ww1.microchip.com/downloads/en/Appnotes/00798a.pdf
The oscillator circuits don't start until page 9
Is wasn't Micrel who used the "TC" prefix - but who was it? I can't seem to remember.
Most of Microchip's driver use the same internal circuit as Figure 11 of the application note, but with smaller or larger output devices.
Examples are MCP1401, MCP1402, MCP1415, MCP1416, TC4426/7/8
 

Papabravo

Joined Feb 24, 2006
17,570
Found the application note (after downloading a dozen and reading through them). Now safely stored on the iPad!
https://ww1.microchip.com/downloads/en/Appnotes/00798a.pdf
The oscillator circuits don't start until page 9
Is wasn't Micrel who used the "TC" prefix - but who was it? I can't seem to remember.
Most of Microchip's driver use the same internal circuit as Figure 11 of the application note, but with smaller or larger output devices.
Examples are MCP1401, MCP1402, MCP1415, MCP1416, TC4426/7/8
For the TC prefix, would you believe Toshiba?
 

eetech00

Joined Jun 8, 2013
2,807
Found the application note (after downloading a dozen and reading through them). Now safely stored on the iPad!
https://ww1.microchip.com/downloads/en/Appnotes/00798a.pdf
The oscillator circuits don't start until page 9
Is wasn't Micrel who used the "TC" prefix - but who was it? I can't seem to remember.
Most of Microchip's driver use the same internal circuit as Figure 11 of the application note, but with smaller or larger output devices.
Examples are MCP1401, MCP1402, MCP1415, MCP1416, TC4426/7/8
The app note refers to TC4420/29.
Will those models serve your purpose?
 

Thread Starter

Ian0

Joined Aug 7, 2020
4,092
Now I've found an old Telcom databook on line, and I'm going to have a trawl through it to see if the oscillator application note came from there, but am I any closer to having a SPICE model?
Improving my ability with SPICE was my lockdown project. Maybe I'll just have to revert to how I did things previously - buy the parts, make a prototype, and see if it works!
 

Thread Starter

Ian0

Joined Aug 7, 2020
4,092
Do you want to take a stab at making a behavioral model for one of those parts?
That’s sort of how I got here!
First, I thought I’d use a 7555 with a complementary emitter follower to drive the MOSFET.
Then I realised that didn‘t work because it should be non-inverting.
So I swapped the complementary emitter follower for a complementary common source inverter, but that had shoot-through problems (maybe not as bad as a bipolar 555, come to think of it)
The I tried a logic-gate inverter, but that said that there were parameters missing.
Then I thought of a fast comparator, and I usually use Microchip, but they have no SPICE models, so I was searching through Linear Technology (whose devices are well represented in my SPICE library, can’t think why!) when I remembered the Microchip application note.
Then I tried some low-side drivers from @Bordodynov ‘s library, but SPICE was taking ages. After half an hour the computer seemed to be getting a bit hot under the collar, so I took pity on it and halted SPICE.
It only then that I asked the good people of AAC for assistance!
 

eetech00

Joined Jun 8, 2013
2,807
I'll be back at breakfast time!
Hi

I've managed to modify the Microchip spice models to work with LTspice.
Sorry for the delay. Microchip models are known to be difficult to work with LTspice.
Attached are models, symbols and Test circuits for LTspice

You will need to use the UIC parameter for their models to work. See below.
You will also need to use .options method=gear (not shown on schematic).

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1637343226213.png
 

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Thread Starter

Ian0

Joined Aug 7, 2020
4,092
Many thanks, all of you.
@eetech00 Could you enlighten me on UIC (Use Initial Condition) and why I should use Gear for integration? (New to me - I looked them up on the wiki)
@Alec_t I see what's going on - you have used a SPICE logic gate with SCHMITT function, and a delay; then switches with defined ON resistance instead of the output MOSFETs, and then some diodes, capacitors and resistors to make the input circuit look realistic. Do the "G"s connected between Vdd and ground simulate its current consumption?
 
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