UCC25660: UCC25660 Bust mode and Test option problem

Marco,

We will release the Simplis model soon. 

There are several ref designs there and you can refer to them for compensator designs.

https://www.ti.com/reference-designs/index.html#search?keyword=ucc2566

Would you please reach out to our FAE for detailed explanation of other questions? We can work with you directly.

Thanks,

Ning

Hi Ning,

Could you let me know when the Simplis model will be released?

I tried to run the simulation on the webbench for UCC2566x, but it shows 'simulation not enabled for this design.'

Due to the UCC2566x being equipped with the new IPPC control, we are unsure how to proceed with the compensator design.

Do you know if other customers have successfully designed compensators? Unfortunately, we do not have the simulation tools or detailed IC information.

Thanks.

Marco,

Simplis model should be available online by the end of this month. 

We have success examples from other customers using IPPC feature with proper compensator design. There are many references on ti.com you can also leverage.

Best,

Ning

Hi Ning,

if there is no model available and no detailed parameter for the IC(with IPPC feature) , how can the customer design the compensator?

try and error on EVB ?

Thanks. 

Marco,

I understand your point and we are working on an app note to discuss this specific topic.

We will release the model by the end of this month. 

In the meantime, please feel free to send the schematic to us for review.

Thanks for the understanding.

Ning

Hi Ning,

Please refer to attachment for our parament for UCC256602 ,please help to check.

Thanks.UCC256602_Feedback to TI.pdf

We will get back to you as soon as we can.

Are you located in Taiwan?

Hi Marco,

Thank you for your patience.

Here are the answers for your questions 3 and 4.

3.TSET pin is used to set the minimum switching frequency at which the IPPC operation is maintained. For better understanding please go through the 7.3.2 section of the datasheet and also the design calculator of UCC25660.  The provided images explain the same.

4.Using LL pin one can configure at what input power level system goes to burst mode.

Here I am attaching the design calculator clip for VLLA-VLLB=0.617V and 1.754V. by using design calculator you will get the HF burst entry and LF burst entry voltages. based on this, when VFB replica goes below HF burst entry voltage but greater than LF burst entry voltage it will go to HF pulse skip mode. (shown in below graph) for better understanding please look at section 7.5.3.2 of the datasheet.

Coming to your question, if you select VLLA-VLLB as 0.617, and if packet stop (VLLB) is chosen as 1V, HF burst entry is 1.429V, LF burst entry is 1.250V of VFB replica. Similarly, with VLLA-VLLB  =1.754, if you choose VLLB as 1V, HF burst entry is 2V, LF burst entry is 1.667V of VFB replica.

Lesser packet stop reduces the power level to exit the LF burst segment.

UCC25660x datasheet

datasheet and design calculator

Your schematic is under review. we will try to get back to you as soon as possible.

Yamini.

Hi Yamini,

Understood and thank you for your explanation.

May I know that when I could get the feedback of shcemait? 

Thanks. 

Hi Yamini, 

As Ning mentioned, the UCC25660x model will be released by the end of this month.

Will the model release ontime?

Thanks. 

Marco,

In the schematic, all the below marked VCC are same?

Marco,

I will get back to you on this.

Hi Yamini,

The secondary side has a 1 turn winding that generates VCC2 for the compensator circuit. 

Thanks.

Marco,

Could you share the updated schematic, since the previous schematic doesn't contain VCC2.

Yamini.

Hi Yamini,

Please refer to the attached PDF file.

And what is the purpose of R21/10Kohmic?

Can I change it to 0ohmic and will it have any impact on closed loop control?

UCC256602_Feedback to TI_20250430.pdf

Thanks for the schematic Marco.

R21 is to calculate the I opto current, so that VFB replica is calculated. You can reduce it to 5Kohm or to any other value (preferably in Kohm) but not to 0.

Hi Yamini,

Thank you for your review and feedback.

I will follow your recommended parameters to modify circuits.

By the way, 

Can you provide the SPICE model of UCC25660x for simulation?

B.R 

Marco

Hi Yami,

Ok, Please provide me the Simplis model when it is avaliable.

Thanks.

Hi Yami,

I just got the information from Ti site, the UCC256602 will never be released, and the part-number will change to UCC256612 due to RTM.

Could I know the differences between these parts？ (package size, electrical characteristics …etc. )  

Thanks.

Hi Jchk and YAMINI,

Thanks for the detailed explanation.

By the way, 

If we want to use UCC256612 to do an open-loop test of a half-bridge LLC.

Do you have any suggestions for this test? Add a variable resistor to pin 5 (FB)?

Thanks.

Marco,

Your query is under the review,

We will get back to you.