My customer is using the UCC28C44 in a high-voltage fly-back. For EMI purposes we need a simple circuit to dither the clock frequency. Do you have any suggestions?
On a related note, do we have any similar devices with this function built in?
Thank you,
Kurt
Hi Kurt,
Thanks for connecting through E2E. Here is a simple frequency dither circuit that can be applied to any general purpose PWM controller. For synchronization that is specific to UCC28C44 type legacy PWM controllers, TI has two excellent app notes that might be helpful for showing how to apply the synchronization signal. Check out SLUA110 and SLUA143:
If you are interested in active clamp flyback, UCC28782 has internal frequency dithering. Also, If you visit the flyback controller landing page on TI.com and click on "QR & DCM Flyback".
In the parametric search you will see an option to select "spread spectrum" (frequency dithering). Search on this and you will retrieve all the controllers that include internal frequency dithering:
Regards,
Steve M
