BUX48 데이터 시트보기 (PDF) - Motorola => Freescale
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BUX48 Datasheet PDF : 8 Pages
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SWITCHING TIMES NOTE
BUX48 BUX48A
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% Vclamp
trv = Voltage Rise Time, 10 – 90% Vclamp
tfi = Current Fall Time, 90 – 10% IC
tti = Current Tail, 10 – 2% IC
tc = Crossover Time, 10% Vclamp to 10% IC
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
using the standard equation from AN–222:
]PSWT = 1/2 VCCIC(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.
INDUCTIVE SWITCHING
5
3
2
TC = 100°C
1
TC = 25°C
0.7
0.5
0.3
0.2
βf = 5
0.1
1
23
5 7 10
20 30
50
IC, COLLECTOR CURRENT (AMPS)
Figure 9. Storage Time, tsv
1
0.5
0.3
TC = 100°C
0.2
TC = 100°C
TC = 25°C
0.1
TC = 25°C
0.05
0.03
tc
0.02
tfi
βf = 5
0.01
1
23
5 7 10
20 30 50
IC, COLLECTOR CURRENT (AMPS)
Figure 10. Crossover and Fall Times
3
2
tsv
1
0.5
0.3
0.2
tc
0.1
tfi
0.05
0.03
TC = 25°C
0.02
IC = 10 A
VBE(off) = 5 V
0.01
0 1 2 3 4 5 6 7 8 9 10
βf, FORCED GAIN
Figure 11a. Turn–Off Times versus Forced Gain
3
2
TC = 25°C
1
IC = 10 A
tsv
βf = 5
0.5
0.3
0.2
0.1
tc
0.05
tfi
0.03
0.02
0.01
0
1 2 3 4 5 6 7 8 9 10
Ib2/Ib1
Figure 11b. Turn–Off Times versus Ib2/Ib1
Motorola Bipolar Power Transistor Device Data
3–405
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