CAS480M12HM3 SPICE

Emma

Dear Engineer,
Hello. I would like to consult two questions:
1. I downloaded the SPICE model of the CAS480M12HM3 module from the official website and imported it into ANSYS via the "Import Twin Builder Models" method. I then constructed a double-pulse test circuit for the CAS480M12HM3 module, as shown in Figure 1. However, the output results for Vgs, Id, and Vds (Figure 2) clearly deviate from practical expectations. I have thoroughly reviewed the code sections of the official model but cannot identify the source of the error. I hereby seek your guidance and would appreciate a response.
2. In the MOSFET module's code, there are 1kΩ resistors between s2 and S, and between D and d2 (illustrated in Figure 3). Could you kindly provide a simple schematic diagram indicating the positions of s2 and d2 within the MOSFET's internal structure?

Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

Bdeboi

Hi Emma,

I have faced this issue with ANSYS' SPICE solver in the past. I believe this is caused by the ddt() function that is not behaving as expected. There's not much I can do about that, unfortunately. As a test, you can try replacing G_cdg, G_cds, and G_cgs with regular capacitors to see if that solves the issue.

For your specific question, R1/R2 are simply there to help with convergence. They are in parallel with GRds and GRbd, which are always going to be on the order of mOhm. GRds/GRbd are just behavioral resistors implemented with a current source (I = V/R).

A few questions/comments:

1. The LTspice models have been updated recently, you may try the latest versions to see if it helps
2. Are you on the latest version of ANSYS? This might be fixed on later versions.
3. Are you using Twinbuilder to develop an electrothermal model? That is, combining this SPICE sim with Icepak? If not, I recommend using LTspice.

Thanks,

Brian

TBhatia

Hi, I hope that this answered your question. If it did, please click on "This question has been answered - Close Discussion" . If you have a follow up question, at a later date, please "Start a New Discussion"