The MMSZ5228BT1G is a 500mW 3.9V Zener Diode manufactured by ON Semiconductor. It is a voltage regulator diode package, with a power dissipation of 500mW and a reference voltage of 3.9V. The MMSZ5228BT1G can be used in a variety of applications, including voltage regulation, protection from over-voltage conditions, AC and DC line protection, and ESD protection. Additionally, the MMSZ5228BT1G is a RoHS-compliant device, featuring an environmentally-friendly, lead-free construction.