An electrical device like this requires a reverse leakage current of 5μA @ 39V.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 47V.For operation, diode reaches 1.2V @ 500mA at the maximum voltage - Forward (Vf).
BZG04-39-HM3-18 Features
reverse leakage current of 5μA @ 39V 5μA @ 39V is the maximum voltage (Tol)
BZG04-39-HM3-18 Applications
There are a lot of Vishay Semiconductor Diodes Division BZG04-39-HM3-18 applications of zener single diodes.