STMicroelectronics announced a new series of high-temperature TRIACs, which maintain full specified performance up to a junction temperature of 150 degrees C, and which deliver outstanding turn-off capability - ideal for appliance motor-control applications, in particular - at their maximum temperature. The devices are available now in volume production, priced from $0.50 to $1.00 in 1000-unit quantities.

    The high- junction-temperature TRIACs will enable manufacturers to lower their costs by using considerably smaller heatsinks, and also allow the end product to benefit from more reliable operation in hot environments. The use of conventional TRIACs, which are specified at 125 degrees C junction temperature, can cause a loss of control of the AC load in environments above this temperature, which can lead to hazardous application behavior, due to device parameter derating above 125 degrees C.

    However, ST's new HiTj Snubberless series requires no derating of any of its parameters up to the maximum junction temperature, and, in fact, achieves a turn-off performance at 150 degrees C, which is three to four times better than normal. In addition, the TRIACs deliver high-noise immunity of up to 1500V/microsecond. Further cost savings are possible for manufacturers through the elimination of RC snubber circuits and noise filters.

    The TRIACs are ideal for use in universal motor-control applications, such as vacuum cleaners, washing-machine drum motors, and industrial drives; in hot environments such as cookers, ovens, kitchen hobs and coffee machines; and for achieving higher power density on PCBs, for heater and high-power motor control. They can also replace conventional TRIACs in closed environments where the ambient temperature is too high. The HiTj TRIAC series is produced in TO-220AB, TO-220AB insulated, and in D2PAK surface-mount packages, for maximum versatility. They are all 600V devices, with current ratings of 8A, 10A, 12A, 16A and 20A. The sensitivity range offered today is 35mA to 50mA, and will soon be extended with 10mA devices.

     Thanks to their bidirectional structure, Triacs are useful in controlling full-wave AC applications. They can be used as an ON/OFF switch, replacing efficiently electro-mechanical relays (providing high degree of flexibility through electronic control, and superior reliability). They are also capable to control power level through AC loads, thanks to a simple phase control circuit.

    Available in general purpose standard configurations, high commutation performance series with ST Snubberless Technology, or high temperature versions for use in harsh environment, they fit any AC applications requiring precise control. A critical intrinsic parameter of the TRIAC is its ability to turn-off properly. The turn-off capability (di/dt)c is strongly dependent on the junction temperature. In order to avoid the risk of losing control at high temperatures due to the inability to switch-off, the new HiTj series have a switch-off capability 3 to 4 times higher than the first harmonic current slope, coping with currents affected by superimposed noise ripple due to loads of the brush motor type.