An electrical device like this requires a reverse leakage current of 2μA @ 2V.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 5.1V.For operation, diode reaches 900mV @ 10mA at the maximum voltage - Forward (Vf).
BZX84-C5V1/LF1VL Features
reverse leakage current of 2μA @ 2V 2μA @ 2V is the maximum voltage (Tol)
BZX84-C5V1/LF1VL Applications
There are a lot of NXP USA Inc. BZX84-C5V1/LF1VL applications of zener single diodes.