TPD4E1B06 diode array structure uses back-to-back diode topology to accommodate bi-directional signaling between –5.5 V and 5.5 V. Each pin has an additional 2 steering diodes, including the ground pin. The Zener diodes are not meant to be forward biased, creating the need for having the steering diodes. If there is +8 V on IO1 and 0V on IO2, the IO1 Zener diode will breakdown and forward bias one of the steering diodes on IO2. The current will then flow out of IO2.