Tyco Electronics is introducing improved CBT series resistors that provide excellent pulse withstand capabilities for circuitry associated with surges, high peak power or high energy, while remaining very stable. Suitable for protection against lightning strikes, advanced characteristics of the highly reliable 0.25W CBT25 and 0.5W CBT50 resistors have been achieved by selecting materials featuring optimum physical properties and by new developments in the manufacturing process.
Low-cost, high-performance CBT25 (maximum voltage 250V) and CBT50 (maximum voltage 350V) resistors are constructed utilising a solid carbon composition – suitable for absorbing high-energy pulses. A direct replacement for hot-moulded carbon composition resistors, solid carbon CBT series resistors offer a much higher pulse handling capability because the entire rod conducts. For example, in case of a fast (<100ms), high-energy pulse, the conductive element is required to withstand all of the energy and absorb all of the heat generated. This is because it takes a finite time for the heat to be transferred from the conductor to the surrounding materials and the air. Therefore, with a film or wire-wound resistor, the film or wire is required to handle the pulse energy. As the mass of wire or film is low, the energy handling capability is low. However, in the case of a solid carbon resistor, the thermal mass is far higher, which results in a higher energy handling capability.
Benefiting from their small size, a range of resistance tolerances and a wide range of resistance values (1R0 to 5M6 for the CBT25 model and 1R0 to 22M for the CBT50 model), improved CBT series resistors are designed for a very wide operating temperature range of -55 to +125degC. The insulation resistance for both versions is 1000M minimum. The devices are supplied in 'ammo pack' boxes of 2000.
