Secondary-side voltage monitor periodically measures its own VDD

The UCC24650 is an easy-to-use secondary-side voltage monitor from Texas Instruments (TI). The device periodically measures its own VDD voltage. A relative drop of 3% from the previous reading triggers an alert signal to a receiving primary-side regulation (PSR) controller. Its low-power consumption helps achieve <5mW standby loss in many applications. An internal 200V MOSFET switch is applied across a ground-referenced rectifier to provide a current-limited pulse to the fly-back transformer secondary winding, which couples the signal to the primary-side controller. This signal is repeated at 33kHz until controller-driven switching activity is detected.