UCD7100 SPICE MODEL FAULTY?

Ian,

Unfortunately, the EULA for LTSpice will not allow us to debug your example in LTSpice. I will take a closer look at the model in PSpice to see if this is something that needs to be addressed.

Good Day Britt,

Thank you for the reply. I did the same simulation in PSpice and varied the CS pin from 0V to 1V over 100 Seconds. The ILIM pin was set to 0.9 Volts and the device tripped at the same voltage as in LTSpice i.e 717 mV .

I think the model is set to trip at a lower voltage than in the datasheet. (When the CS pin exceeds ILIM - approximately 200 mV instead of 25 mV.)

Let me know if i should send you any of the data that i used,

Thanks in advance for the help

Ian,

I, too, have confirmed this value. I get the 717mV as well. I am investigating an equation in the model that sets the ILIM threshold internally and does not use the actual value of the ILIM voltage. The equation is in the unencrypted model:

E_ABM5         ILIM_DIGITAL 0 VALUE { IF(V(ILIM)<0.75,{1.4495*V(ILIM)-0.3622}, {0.1176*V(ILIM)+0.6368})    }

In your example, ILIM is set to 0.9, so the second equation is evaluated and gives 0.742. The 25mv is subtracted from that in another portion of the circuit, which gives you the 0.717 value.

I believe that this has something to do with the differing thresholds of ILIM based on the voltage values provided in the datasheet table 7.5. However, I have not yet confirmed this yet. The value is also limited between 0.23V and 1.025V.

Hi Britt,

For my application I'll have my ILIM pin set to 0.55 V . I tested it at this value aswell which seems to be within the acceptable range for ILIM and it trips at approximately 410 mV .

I'm not too familiar with the NGSpice circuit notation so I have no idea where the error could be but it looks like that line could be the problem. Please let me know if you get it working at all.

Thanks a lot for the help!

Ian,

I am checking into the issue. As I stated before, the ILIM voltage value is not being used to set the CLF trip point, an internal value is being used that I am trying to verify.

Hey Britt,

Just wanted to know if you were able to fix the model?

Thanks for all help.
Ian

Ian,

Unfortunately, there was more wrong than just a simple fix to the model. The datasheet has an error in it and this caused the way the model was implemented to behave incorrectly. I had to verify that the datasheet was incorrect and what the proper implementation of the fix should be. We have identified it and it will be submitted for update shortly. I do not have an estimate of when the model update will be completed.

I do appreciate the report of the issue. In this case, it was not a simple task to find the root cause.

I will post a follow-up when I have more information about the update and the timeframe for it.

Thanks for the effort Britt, Could you please elaborate on what is wrong with the datasheet? What needs to change in the datasheet?

The follow-up will be much appreciated!

Thanks again for all the help

Thanks for the effort Britt, If at all the model is fixed within the following month please let me know.

Otherwise thank you for all the help

Ian

Ian,

The updated mode was released to the web. It may take up to 48 hours to appear, however, the model files should be present by Monday at the latest.

Thanks for your patience.

Good day Britt,

I just want to double check something with you, the datasheet specifies that the device trips when CS exceeds (ILIM-25mV), Does it trip at this level or when CS exceeds ILIM?

Thanks for the outstanding service.

Ian

Ian,

I believe that when CS exceeds ILIM-25mV. I do not believe that this changed in the model.