TINA/Spice/LM3481: PSpice/LM3481

Hi,

The PSpice model available on the web doesn't support startup behavior. It can be used to observe steady-state nature of the model only.

Level shifter:
From the block diagram snapshot, we can see that this block changes the reference of Isen pin from PGND (external ground reference) to AGND (device's internal reference). I hope it clarifies your query.

Kindly let me know if anything else is needed.

Thanks,
Abhisek

Dear Sir:

Thank you for your reply.

I know the function of levelshifter, it cannot be a constant, but I don't know its value. So I cann't realize the startup process in simulation. While we needs to know the startup behavior, the IC is used in many devices of our company, so please tell me the value of the LevelShifter during the startup process.

Waiting for your reply.

BEST REGARDS.

My company must realize the startup process in simulation, So I must know the value of Level shifter. Just know the function of Level shifter is not enough, and I know it's used as a DC Bias before.

Hi,

I will discuss with the design team and get back to you with more details rearding the level sifter block.

Thanks,
Abhisek

Dear Sir:

Thank you for your reply.

I need to realize the startup process in simulation. Maybe it's be realized by PSpice or Simulink, so please tell me the true startup process of LM3481, other than a packaged PSpice model.

Besides, I think the softstart is related to 1.275V Reference. I suppose it's a ramp signal not a step signal.

Please tell me more details.

Thank you very much.

Hello,

The level sifter is basically equivalent to the normal COMP to PWM offset. Instead of subtracting this the value for the COMP signal it is added to the current sense signal. In current mode control these are equivalent actions. This value can be estimated to be around 600mV as seen in the datasheet specifying the minimum COMP voltage.

Can you please clarify what you mean by the startup process? The UVLO pin needs to be above the specified rising threshold. The easiest way to get an idea of the start-up procedure is to use one of the models that is online.

Thanks,

Garrett

Dear Sir:

I got your idea. But the COMP voltage is about 1.4V in test. While the Level Shifter and Isen Voltage is about 600mV~820mV, so the PWM will always be low level. The gate will always be high level. It's unreasonable. So the V-I Converter and I-V Converter is not 1:1?

I want to know how the soft-start works. The models online cannot realize startup process. Abhishek Tripathy has told me that. I want to know the soft-start principle so that I can model it by myself.

Thanks.

Hi,

Happy New Year.

Thanks for your patience. Softstart feature is showing some irregularity. We are working on implementing it properly and will be updating the model available on the web in around 2-3 weeks time.

Thanks,

Abhisek

Dear sir:

Is there any progress?

Besides is it possible that the improved model can simulate the startup-stop and restart process? 

Beacause the process is important to products of customer.

Dear sir:

Where is the new model?I still cannot see it.

Hi Sir,

Model's development is in progress and we are trying to release the model on web by 02/15.
We really appreciate your patience on this and sorry for inconvenience has been caused.

Regards,
Saket