An internal VCC shunt regulator is incorporated into each member of the UCCx813-x family to limit the supply voltage to approximately 13.5 V. A series resistor from VCC to the input supply source is required with inputs above 12 V to limit the shunt regulator current. A maximum of 10 mA can be shunted to ground by the internal regulator. The internal regulator in conjunction with the device’s low start-up and operating current can greatly simplify powering the device and may eliminate the requirement for a regulated bootstrap auxiliary supply and winding in many applications. The supply voltage is MOSFET gate level compatible and requires no external Zener diode or regulator protection with a current-limited input supply. The UVLO start-up threshold is 1 V below the shunt regulator level on the UCCx813-[2,4] devices to ensure start-up. It is important to bypass the device's supply (VCC) and reference voltage (REF) pins each with a 0.1-µF to 1-µF ceramic capacitor to ground. The capacitors must be placed as close to the actual pin connections as possible for optimal noise filtering. A second, larger filter capacitor may also be required in offline applications to hold the supply voltage (VVCC) above the UVLO turnoff threshold during start-up.