UCC28950 - some questions

Hirotaka Matsumoto

Other Parts Discussed in Thread: UCC28950

Hi all

Would you mind if we ask UCC28950?

<Question>
On the datasheet, ADEL voltage is CS voltage with the partial resistance.
In this case, don't we need consider divided cases as follows?

On the application note SLUA560C, ADEL voltage is inserted VREF voltage with the partial resistance.
In this case, is it no relation with CS voltage? Otherwise, is it fixed voltage?
We have following questions;
1. tABSET=346ns from calculation formula (122)
2. RDA1, 8.25kohm(given value)
3. tABSET=346ns > 155ns, VADEL is defined =0.2V.

RDA2=348ohm from calculation formula (124) and (125)
4. RDELAB=30.1kohm from calculation formula (127)

5. In relation with 1, in case of tABSET<155ns, VADEL=1.8V, ADEL=1.8V

Is our recognition correct?

-Application note(http://www.ti.com/lit/an/slua560c/slua560c.pdf)

We do need your help.

Kind regards,

Hirotaka Matsumoto

over 7 years ago

0 John Stevens over 7 years ago

TI__Expert 7395 points

Matsumoto-san,
Thanks for the interest in TI here. I've contacted the product group for this part. they should reply soon.
Regards,
John

0 Brian Johnson96 over 7 years ago in reply to John Stevens

TI__Expert 3200 points

Matsumoto-san,

The expert is out of office for a few days, can we answer this next week?

0 Hirotaka Matsumoto over 7 years ago in reply to Brian Johnson96

Guru 27565 points

Brian san

Thank you for your reply.
We are waiting for your reply.

Kind regards,

Hirotaka Matsumoto

0 Hirotaka Matsumoto over 7 years ago in reply to Hirotaka Matsumoto

Guru 27565 points

Hi team

Could you let us know your circustance?

Kind regards,

Hirotaka Matsumoto

0 Colin Gillmor over 7 years ago in reply to Hirotaka Matsumoto

TI__Mastermind 25570 points

Hello Matsumoto-san

Yes - the application note SLUA560C does show a fixed voltage at the ADEL pin. This design was done some years ago and the designer found that there was little benefit in this particular design of using the ADEL function so he fixed it at a constant value. He chose 0.2V because that is one of the test conditions for the ADEL function in the DS.

I think your understanding of the equations is correct.

In general, the ADEL and ADELEF functions will allow a designer to improve the efficiency of their design a little. The improvement will be greater at higher power levels. The EVM runs at 600W so there is only a small improvement. I would recommend that a designer uses the ADEL function - connect the potential dividers at the ADEL and ADELEF pins to the CS pin and then adjust them during product development - as is suggested in the datasheet for the device.

Hope this answers your question - please feel free to re-post if you need more information.

Regards
Colin

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UCC28950 - some questions