An electrical device like this requires a reverse leakage current of 50nA @ 18.9V.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 27V.For operation, diode reaches 1.1V @ 200mA at the maximum voltage - Forward (Vf).
BZV55C27 Features
reverse leakage current of 50nA @ 18.9V 50nA @ 18.9V is the maximum voltage (Tol)
BZV55C27 Applications
There are a lot of Microsemi Corporation BZV55C27 applications of zener single diodes.