Bourns BD902

Power Bipolar Transistor, TO-220AB, Plastic/Epoxy, 3 Pin

These devices are primary protector components for semiconductor arrester assemblies intended to meet the generic requirements of Telcordia GR-974-CORE or ITU-T Recommendation K28 (03/93). To conform to the specified environmental requirements, the 9ELx must be installed in a housing which maintains a stable micro climate during these tests (e.g. FIGURE I.1/K28). The protector consists of a symmetrical voltage-triggered bidirectional thyristor. Over voltages are initially clipped by breakdown clamping until the voltage rises to the break over level, which causes the device to crowbar into a low-voltage on state. This low-voltage on state causes the current resulting from the over voltage to be safely diverted through the device. In usual applications, the high crowbar holding current prevents d.c. latchup as the diverted current subsides. This 9ELx range consists of two voltage variants to meet various maximum system voltage levels. They are designed to voltage limit and withstand the listed international lightning surges in both polarities. These monolithic protection devices are constructed using two nickel plated copper electrodes soldered to each side of the silicon chip. This packaging approach allows heat to be removed from both sides of the silicon, resulting in the doubling of the devices thermal capacity, enabling a power line cross current capability of 10 A rms for 1 second. One of the 9ELx's copper electrodes is specially shaped to promote a progressive shorting action (at 50/60 Hz currents greater than 60 A). The assembly must hold the 9ELx in compression, so that the cell electrodes can be forced together during over stress testing. Under excessive power line cross conditions the 9ELx will fail short circuit, providing maximum protection to the equipment.