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MJ10020 MJ10021 5 Motorola Bipolar Power Transistor Device Data SWITCHING TIMES NOTE In resistive switching circuits, rise, fall, and storage times have been defined and apply to both current and voltage waveforms since they are in phase. However, for inductive loads which are common to SWITCHMODE power supplies and hammer drivers, current and voltage waveforms are not in phase. Therefore, separate measurements must be made on each waveform to determine the total switching time. For this reason, the following new terms have been defined. tsv = Voltage Storage Time, 90% IB1 to 10% VCEM trv = Voltage Rise Time, 10–90% VCEM tfi = Current Fall Time, 90–10% ICM tti = Current Tail, 10–2% ICM tc = Crossover Time, 10% VCEM to 10% ICM An enlarged portion of the inductive switching waveforms is shown in Figure 7 to aid in the visual identity of these terms. For the designer, there is minimal switching loss during storage time and the predominant switching power losses occur during the crossover interval and can be obtained us- ing the standard equation from AN–222A: PSWT = 1/2 VCC IC (tc) f In general, trv + tfi ^ tc. However, at lower test currents this relationship may not be valid. As is common with most switching transistors, resistive switching is specified at 25 °C and has become a benchmark for designers. However, for designers of high frequency con- verter circuits, the user oriented specifications which make this a “SWITCHMODE” transistor are the inductive switching speeds (tc and tsv) which are guaranteed at 100_C. Figure 10. Typical Turn–On Switching Times IC, COLLECTOR CURRENT (AMPS) 2.0 3.0 5.0 7.0 10 20 60 Figure 11. Typical Turn–Off Switching Times IC, COLLECTOR CURRENT (AMPS) Figure 12. Thermal Response t, TIME (ms) 1.0 0.01 0.1 0.1 1.0 10 100 10000 R θJC(t) = RθJC R θJC(t) = 0.7°C/W MAX DETERMINE t2 FOR POWER PULSE AND READ r(t) TJ(pk) = TC + P(pk) R θJC(t) P(pk) t1 SINGLE PULSE 1000 0.01 0.02 0.03 0.05 0.07 0.1 0.2 0.3 0.5 0.7 1.0 2.0 3.0 5.0 7.0 10 0.02 0.03 0.05 0.07 0.1 0.2 0.3 0.5 0.7 1.0 2.0 tf VCC = 175 V IC/IB = 25 VBE(off) = 5 V TJ = 25°C VCC = 175 V IC/IB = 25 TJ = 25°C ts td tr 40 0.6 0.8 1.0 2.0 3.0 5.0 7.0 10 20 60 40 0.6 0.81.0 RESISTIVE SWITCHING |
