Hello everyone,
currently we are facing a problem with the output voltage of the UCC28710. When our device is influenced by indirect ESD or a burst pulse on the supply cable, the output voltage falls shortly below the reset voltage threshold.
We can not change the layout, but we must use the current design as it is. So we can change components, or add a limited number of components which are already in the layout, but not populated.
Applying larger capacitors (primary and secondary) was not helpful. But when adding a capacitor of 4p7 on the Voltage-Sense pin (2) of the UCC28710 the secondary voltage is stable enough to prevent the problems. While capacitors are generally not recommended on the voltage-sense pin, this is a very small value which does not seem to have a negative effect on the switching behavior.
What are the critical parameters that we should watch out for in our measurements to make sure that we are not deteriorate the performance?
(We are using a voltage divider of 82k / 20k at the auxilary winding).
Thank you for the advice,
Horst