UC3854: Synchronizing the UC3854

David Kravitz

Prodigy 70 points

Part Number: UC3854
Other Parts Discussed in Thread: UCC28063A, UCC3895

Hello,

I am looking for some support on synchronizing this part to a downstream PWM converter.

Please advise.

Thanks!

over 3 years ago

0 Mike O' over 3 years ago

TI__Guru 66135 points

Hello,

I have assigned and applications engineer to look into this for you.

They should be getting back to you shortly.

Regards,

0 David Kravitz over 3 years ago in reply to Mike O'

Prodigy 70 points

Ok, thank you.

0 David Huang33 over 3 years ago in reply to David Kravitz

TI__Genius 9140 points

Hi David:

there is no a pin special designed or showed PFC ok signal for downstream PWM controller, I would suggest you can add external circuit by sampling PFC bus voltage through Vsense pin and compare with a reference votlage with a comparator or amplifier to get the PFC OK signal for downstream PWM controller.

UCC28063A has a pin"PWMCTRL" that designed for downstream PWM. You can use the same idea for UC3854.

Hope this helps you.

0 David Kravitz over 3 years ago in reply to David Huang33

Prodigy 70 points

I am not looking for a PFC ok signal. I am looking to synchronize the oscillator to an external clock. Please advise.

0 David Huang33 over 3 years ago in reply to David Kravitz

TI__Genius 9140 points

do you mean using external clock to control the UC3854 frequency?

0 David Kravitz over 3 years ago in reply to David Huang33

Prodigy 70 points

Yes, please advise ASAP. I did find application note Slua245.

On another note, I need to synchronize three UCC3895's to an external clock. I see it has a bidirectional SYNC pin.

The data sheet is very limited on how to connect this pin to other UCC3895 ICs. Please provide any additional information.

Thanks

0 David Kravitz over 3 years ago in reply to David Kravitz

Prodigy 70 points

Can I please get some real support here?

0 David Huang33 over 3 years ago in reply to David Kravitz

TI__Genius 9140 points

Hello David,

it is a pity that you are not satisfy with the E2E support. in order to have a good communication on the post, you also need to respine to the post ASAP.

can I know whether SLUA245 answers your question?

For UC3895, I would suggest you can refer the SLUA609 as a reference.

I would also suggest you can create a new post for UC3895 if you still have a question.

The E2E needs to cover a device in one post.

Power management

Power management forum

UC3854: Synchronizing the UC3854