The heat dissipated by the Schottky blocking diodes traditionally used to protect a load from faulty power supplies is high, relating directly to its hefty 0.5V forward voltage drop. Replacing the diodes with low on-resistance MOSFETs, with typical forward voltages of under 100mV, means power dissipation is greatly reduced. The ZXGD3102 is therefore purpose designed to control MOSFETs in high-reliability N+1 redundant power systems.
Sinking a peak turn-off current of 5A, the controller’s gate drive is able to achieve a typical MOSFET turn-off time of 160ns, ensuring the rapid load protection that’s needed to avoid any variation in bus voltage in the event of a power supply failure and hot-swapping. To meet the fault handling requirements, turn-on time can be adjusted to enable a smooth hand over between supplies. The ZXGD3102’s input voltage blocking capability is 180V.
The chip is housed in the compact SM8 package and requires a minimal external component count. It uses a 5 to 15V low current bias rail, which is easily derived using a miniature zener diode. The ZXGD3102 active OR’ing controller is priced at $0.98USD in quantities of 1K.