Synchronization frequency of UC2853A

Shinichi Inoue

Guru 19961 points

Other Parts Discussed in Thread: UC2853A

Dear Specialists,

My customer is considering UC2853A it's frequency is 25kHz to 50kHz by output synchronization.

According to the application note(U-159), it was recommended 95kHz to 115kHz.

But I think it has a possibility to use from 25kHz to 50kHz because it is far enough from DC.

Could you please advise possibility and any worries with device inside operation?

If it is possible, please tell me the way to make it happen.

(I think that is U-159 of Figure 11. I am happy to give me additional suggestion. )

If it is impossible, please tell me the reason.

Best regards,

Shinichi

over 9 years ago

0 Peter Meaney over 9 years ago

TI__Mastermind 31580 points

Hi Shinichi,

This is an older device, let me see what I can find out.

Regards

Peter

0 Shinichi Inoue over 9 years ago in reply to Peter Meaney

Guru 19961 points

Dear Peter

Thank you for your reply.

All right.

I am looking forward to your answer.

Best regards

Shinichi

0 Peter Meaney over 9 years ago in reply to Shinichi Inoue

TI__Mastermind 31580 points

Hi Sinichi,

Reading the app note slua080, see link below. It appears that the UC2853A can only be synchronised to frequencies in the range of 95kHz to 115kHz. There are more details in the apps note on the synchronisation circuit.

Regards

Peter

www.google.de/url;rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad=rja&uact=8&ved=0CCoQFjAB&url=http%3A%2F%2Fwww.ti.com%2Flit%2Fpdf%2Fslua080&ei=lcT-VOy7Cqij7AbX7IHYCQ&usg=AFQjCNEqkC8v3xALFEr7YxVWK__qOkpkgg&sig2=u-dJS4dKP3sIx4ywyluGkg&bvm=bv.87611401,d.ZGU

0 Shinichi Inoue over 9 years ago in reply to Peter Meaney

Guru 19961 points

Dear Peter

Thank you for your reply.

I have already know that application note and that description.

But it is not enough to understand.

Could you please advise me more detail?

The customer really have to use 25kHz to 50kHz.

He wants to know a solid reason why not to use 25kHz to 50kHz.

Best regards,

Shinichi

0 Peter Meaney over 9 years ago in reply to Shinichi Inoue

TI__Mastermind 31580 points

Dear Shinici,

Its not possibel to sync the controller to a lower frequency as the internal osccilator will terminate the cycle early and reset the PWM cycle. It is only possible to syn to a higher frequency and reset the PWM cycle before the internal oscillator does.

Regards

Peter

0 Shinichi Inoue over 9 years ago in reply to Peter Meaney

Guru 19961 points

Dear Peter

Thank you for your reply.

I'll feedback your answer to the customer.

If he has an additional question, I will consult with you.

I appreciate your great help.

Best regards,
Shinichi

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Synchronization frequency of UC2853A