TPS54308: incorrect simulation result

Hi 

You can connect a external voltage source to EN or connect to Vin through a resistor divider. Please see section 4.3.5 Enable and Adjusting undervoltage lockout section in datasheet for more details.  EN >1.21 makes the circuit enabled. don't let EN>7V.

What simulation tool did you use?

The TPS54308 soft start time is 5ms, you might se the simulation time longer than that ,like 6ms.

Thanks and best regards.

Hi Gui,

Thank you for your help. 
I used Pspice. 
I run the simulation for more than 10ms runtime and tried it with both a constant DC source in the range of 1.21V and 5V as per the datasheet, and also using a resistor divider, but it doesn't work as expected. 
If you have simulated it before, please share it with me.

Hi Ashenafi

I didn't simulate this before, but I think you can share your simulation file, and I will try from my side. You can send to bella-he@ti.com. Also, may I know what's your application end equipment and what's the 5V and 3.3V for?

Thanks and best regards. 

Hi Gui,

I tried to send it to you from outlook. but as you can see from the screenshot attached it is not getting delivered to you. can you send me a working email please? 

Hi Ashenafi

Can you please try attach the zip file here?

Thank you

Hi Gui,

Ok, here it is.tps54308ddcr 12v to 5v and 3 point 3v-2024-11-29T08-47.zip

Hi Ashenafi

I ran the simulation and the error information is related to the transformer model: Let me check about this tomorrow and will keep you updated.

Thanks and best regards.

Hi Gui,

I manually added the transformer model and able to run it. But the simulation result is not correct as expected. 
Ok, check it and let me know what you have found.

Hi Ashenafi

Let me check about this...Can you please share what's the incorrcect simulation result be like?

Thank you

Hi Gui,

All right. On the transformer's secondary side, I was unable to obtain a 5V output. Please simulate it and share the result with me. 

Hi Ashenafi

I notice that the secondary output are floating. Can you connect the secondary Cout_negative terminal to the GND same as primary output? (I know it need to be isolated, but it might need to be connected to the reference ground in simulation)

Thanks and best regards.

Hi Gui,

I tried it before, and it doesn't make any difference. 
can you share your simulation result?

Sorry for late as and I will share the simulation from my side tonight.

Thanks and best regards.

Hi Gui,

Ok I will wait for you.

Hi Ashenafi

I replaced the transformer with inductor and the simulation still failed, the issue seems related with the TPS54308. slum585c(1).zip

I download the pspice model from ti.com and the attached simulation should work.

Thanks and best regards.

Hello Gui

I have done that before, and I see that connecting the SEC_GND and GND pins together makes the simulation work, but in a real-world application, those pins shouldn't be connected together, right? I would like to know why the TIDA-010216 auxiliary power supply circuit that I included at the start of this conversation isn't functioning. Additionally, I developed and tested a prototype PCB board, and while I receive an approximate 5.4V output at the SEC_5V pin, the 3V3 and 3V3_COM outputs are not functioning; instead, I get less than 1V. Would you please refer to the TIDA-010216 reference design and help me to fix this problem?

Hi Ashenafi

I see that connecting the SEC_GND and GND pins together makes the simulation work, but in a real-world application, those pins shouldn't be connected together, right? ----Yes. 

Did you check the simulation files attached in my last post, does it work? I think the simulation issue is solved, right?

For the test result, can you please check the SW voltage waveform? 

Thanks and best regards.

Hi Gui,

Ok

yeah, I checked, and it works, but you used different resistor and capacitor values, also you did not include the diodes.

Ok I will check and let you know.

Thank you.

Hi Ashenafi

You can change the resistor &capacitor values and include the diodes yourself.

Thanks and best regards.

Hi Gui,

Ok, I will do so.

Thanks Again for your support.