UCC28950: UCC28950 question

Hello,

Your inquiry has been received and is under review.

Regards, 

Hello,

It seems that there is a typo in RABSET equation that gives the incorrect value.  Thankyou for pointing that out.  It will be updated on the next revision of the data sheet.

You also mentioned that when short ADEL to ground that your expected delay is longer than you calculated.  Did you verify this on the outputs of the UCC28950?  There could be delays due to the driver and/or gate drive transformers you are using.

Regards,

UCC28950 question.

Hello,

Thank you for contacting us.

I understand the typo in the RABSET expression.

If so, please tell me the correct formula.

There is a statement in the previous application that if ADEL is shorted to ground, KA = 0,and I am calculating with KA = 0.  Is this still valid?　If it is invalid, please tell me the correct method.

Regarding your question about dead time measurement, I am checking the waveform of the output terminal of UCC28950.

This is confirmed using the output of the UCC28950, so it does not include delays caused by the driver IC used.

Also, I have not received an answer to the following questions ④ and ⑤ that I asked last time,so please answer them as well.

④How much variation should we assume for this IC itself with respect to dead time?

⑤I would like to receive information about IC variations, changes due  to temperature fluctuations and aging deterioration.

We are running out of time, so we would appreciate your cooperation in responding as soon as possible.

Regards,

Hello,

You had highlighted in your notes that were high lighted.  Please see below.

"As an example, assume RAB = 15 kΩ, CS = 1 V and KA = 0.5. In that case, it says TABSET will be about 90 ns. However, when Equation 3 is actually calculated, TABSET = 82.4 ns, which does not match."

The following table from the data sheet shows the accuracy of the delays over temperature.

Regards,

UCC28950 question.

Hello,

I received information about the accuracy of this IC against temperature changes.
Thank you very much.
Is it safe to assume that this information also includes the variation standards for the IC itself?
Also, how should we think about aging deterioration?

Furthermore, regarding the RABSET formula, which had a typo in the application, we have not yet received an answer for the correct formula.
Currently, calculation cannot be started, and it is also not possible to confirm whether the calculated values match the actual values.
This matter is the most important.

As time is running out, we appreciate your prompt response.

Regards,

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

Hello,

These device parameters are documented in the data sheet.  I am not sure what you mean by variations standards can you clarify?

In regards to aging of the devices the following link has information that should be helpful in answering these questions.  

https://www.ti.com/support-quality/faqs/product-shelf-life-faqs.html?keyMatch=SHELF%20LIFE

The typo in RABSET was in the answer not the calculation.  So you should be able to use this calculation.  You had verified it but it was slightly off.  I had asked you to check directly at the outputs for clarification.  If you don't have time that is O.K.

In regards to the design itself you will have to fine tune the timing for ZVS.  This is because estimating the exact switch node capacitance is difficult.  I would recommend loading the design with 10% load and then setting the delays to valley switch.

Regards,