Date: 19/03/2009

Active OR'ing controller chip for shared power system designers

Diodes Incorporated introduced an active OR'ing controller chip, enabling shared power system designers to replace heat-dissipating blocking diodes with high efficiency MOSFETs. The ZXGD3102 ensures cool running, and reliable operation in up-time critical telecom, server and mainframe applications.

The heat dissipated by Schottky blocking diodes, traditionally used to protect a load from faulty power supplies, relates directly to the hefty 0.5V forward voltage drop. Replacing the diodes with low on-resistance MOSFETs, which have typical forward voltages of under 100mV, means that power dissipation is greatly reduced. The ZXGD3102 is specifically designed to control MOSFETs in 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 is 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 handover between supplies. The ZXGD3102's input voltage blocking capability is 180V. It uses a 5 to 15V low-current bias rail, which is easily derived using a miniature Zener diode. This device is available in SM8 package.