JAJSE40A October 2017 – February 2018 UCC28780
Since RDM and RTZ pins are the critical programming pins for ZVS control, UCC28780 offers both open and short protections to those pins. After VVDD reaches VVDD(ON), a fixed voltage level is applied to the pin and the corresponding current level flowing out of the pin is sensed to detect the pin fault event. As a result, too small of a current represents the pin-open state, and too large of a current represents the pin-short state where the short current level is self-limited. When the fault event is identified, one UVLO cycle of VDD is triggered as the protection response.