JAJSE40A October 2017 – February 2018 UCC28780
The output of the internal 5-V regulator of the controller is connected to this pin. It requires a high-quality ceramic-bypass capacitor (CREF) to GND for decoupling switching noise and lowering the voltage droop as the controller transitions from wait state to run state. The minimum CREF value is 0.1 μF, and a high quality dielectric material should be used, such as a X7R. The output short current (IS(REF)) of the REF regulator is self-limited to approximately 14 mA. 5-V bias is only available after the under-voltage lock-out (UVLO) circuit enables the operation of UCC28780 after VVDD reaches VVDD(ON).