UCC28070: EXTERNAL CLOCK SYNC

ilia hadzhiev

Part Number: UCC28070

hello
i have a couple of question .
1. If I use external clock sync what is the maximum frequency range that i can achiev. For an example can i achiev 50% dither magnitude of fpwm.
2. And i work with 30kHZ fpwm can i work below 30kHz in the low line voltage , and can the ucc28070 controller handle with that. Or i should go to hihger PWM frequency.
3. I cant understand what is the value of ksync ( ramp reduction factor) it should be equal to 1 or somthing else.

Regards
ilia

over 7 years ago

0 Yunsheng Qu over 7 years ago

TI__Genius 9790 points

Hi, Ilia

If an external frequency source is used to synchronize fPWM and frequency dithering is desired, the external
frequency source must provide the dither magnitude and rate functions as the internal dither circuitry is disabled
to prevent undesired performance during synchronization.

So everything is related to external frequency signal.

regards,

0 ilia hadzhiev over 7 years ago in reply to Yunsheng Qu

Prodigy 160 points

Hi Yunsheng

what about Ksync (ramp reduction factor) i did my calculations with Ksync = 1 is that correct

regards,

Ilia

0 Benjamin Lough over 7 years ago in reply to ilia hadzhiev

TI__Mastermind 27115 points

Hi Ilia,

You can find the equation for Ksync in this post:e2e.ti.com/.../1615868

Best Regards,
Ben Lough

0 ilia hadzhiev over 7 years ago in reply to Benjamin Lough

Prodigy 160 points

Access Denied (Note: a common reason this message is displayed is because the thread was deleted)

0 Benjamin Lough over 7 years ago in reply to ilia hadzhiev

TI__Mastermind 27115 points

Hi Ilia,

Here is the relevant text: The factor Ksync in equation (23) is what adjusts the gain as described in the text of page 16. The obscure part is that Ksync is the inverse of the modification factor used in equation (8) on page 16. In other words, if Rrt is modified by 1.1, then Ksync = 1/1.1 = 0.909. If Rrt is increased by 1.25, then Ksync = 0.8, etc

Best Regards,
Ben Lough

Power management

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UCC28070: EXTERNAL CLOCK SYNC