LM5023: Power management forum,

Hi, Abhishek 

Thank you for your interested in TI solutions. 

The COMP waveform you provided is a little wired. Since the internal voltage source of COMP pin is only 5V, but the max value which shows is between 12.5V~7.5V. I think it should be VCC waveform because this range is also closed to VCCON(12.8V typ.)/VCCOFF(7.5V). 

After checking your schematic, I thought it could be caused SS cap(C9) is too big. The current source of SS is 22uA, and SS voltage would limit VCOMP to control DRV signal. 

In your case, the C9 is 150nF. Before the output reaches the target. The COMP keeps 5V around. Thus, the SS time is 35ms. 

So would you please try to reduce C9 to 10nF first?

TI has a similar design 65W/19V EVB.  the SS is 0.01uF(10nF).

You may refer the design as below. 

LM5023-2NBEVM Evaluation board | TI.com

Please let me know if this help you. 

Regards, 

Wesley 

Changed SS cap to 10 nF but still getting same error.

Hi, Abhishek:

It seems the VCOMP is not correct.  VCOMP should be pull high by internal voltage source when VCC reaches VCCon. The slew rate follows by SS voltage. 

Would you please disconnect F1, and connect 42kohm from COMP to GND to simulate open loop operation? 

No, still not working, getting the same error. If you want, I can upload the simulation file.

Hi, Abhishek:

I down load the LM5023's SPICE model and TINA model. Both of them are okay to use. The simulation of LM5023's model works well.. 

https://www.ti.com/lit/zip/snvm463

would you please download the model and check if works again?

Also, please share the simulation file to me. I would try to fix it. 

Wesley

Hii Wesley...

Yeah, I have tried but still not working. I am uploading the simulation file please check.

Thanks

LM5023.DSN