Hybrid BJT/MOSFETs deliver 'best of both worlds' performance
The new ESBT family resolves the power supply designer's dilemma of choosing either bipolar junction transistors (BJT), characterised by low conduction losses but slow switching speeds, or MOSFETs, with their fast switching speeds but high conduction losses. Instead, by incorporating a BJT and MOSFET connected in a cascode configuration and housed in a single package, the new devices retain the benefits of each approach while eliminating the disadvantages e.g. conduction losses are comparable to those of a single BJT while switching frequencies over 130kHz can be achieved under hard (snubberless) switching conditions, which the devices can safely handle thanks to the square reverse bias safe operating area resulting from its cascode configuration and dedicated bipolar technology
Another significant benefit of the new devices is a high voltage capability of up to 1.7kV, which allows designs to operate with a higher flyback voltage and, consequently, a higher duty cycle. This, in turn, allows the power supply to handle higher powers or to operate within a wider range of input voltage.
Members of the new family include the STC03DE170, STC05DE150 and the STC08DE150, which feature breakdown voltages of 1.7, 1.5 and 1.5kV, respectively, and on-resistances of 0.55, 0.17 and 0.11 Ohms, respectively. In comparison, 1500V power MOSFETs typically exhibit on-resistances in the range 5-9 Ohms. All three devices feature a Vcs(sat) value of 0.9V, minimising conduction losses, while the absence of tail currents also minimises turn-off losses. As a result, the new ESBT family enables cooler and more reliable operation in all power supply applications from 30W to 150W.
All of the new devices are housed in a custom-designed four-lead TO-247 package featuring a lateral collector pin to increase the clearance between high voltage and low voltage pins, maximising the system reliability in harsh industrial environments. The STC03DE150, STC03DE170 and STC08DE150 are available in production volumes, with pricing for sample (100pcs) quantities of $3.10, $3.30 and $3.60, respectively.
Through its Application Laboratories and Competence Centres, ST provides comprehensive support for the new ESBT family, including application notes and reference design boards.
This press release is also available at http://www.st.com/stonline/press/news/year2005/p1646d.htm ... with links to further information on the ESBT family.
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