MJE13002 MJE13003
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% 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 us-
ing the standard equation from AN–222:
PSWT = 1/2 VCCIC(tc)f
In general, t rv + t fi
t c. 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.
]
RESISTIVE SWITCHING PERFORMANCE
2
1
0.7
0.5
t, TIME (
µ
s)
0.3
0.2
0.1
0.07
0.05
0.03
0.02
0.02 0.03
td @ VBE(off) = 5 V
tr
VCC = 125 V
IC/IB = 5
TJ = 25°C
t, TIME (
µ
s)
10
7
5
3
2
1
0.7
0.5
0.3
0.2
0.1
0.02 0.03
tf
ts
VCC = 125 V
IC/IB = 5
TJ = 25°C
0.05 0.07 0.1
0.2
0.3
0.5 0.7 10
20
0.05 0.07 0.1
0.2
0.3
0.5 0.7
1
2
IC, COLLECTOR CURRENT (AMP)
IC, COLLECTOR CURRENT (AMP)
Figure 8. Turn–On Time
Figure 9. Turn–Off Time
r(t), EFFECTIVE TRANSIENT THERMAL
RESISTANCE (NORMALIZED)
1
0.7
0.5
0.3
0.2
D = 0.5
0.2
0.1
P(pk)
0.1
0.07
0.05
0.03
0.02
0.05
0.02
0.01
SINGLE PULSE
0.02 0.03
0.05
0.1
0.2 0.3
0.5
Z
θJC(t)
= r(t) R
θJC
R
θJC
= 3.12°C/W MAX
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME AT t1
TJ(pk) – TC = P(pk) R
θJC
(t)
t1
t2
DUTY CYCLE, D = t1/t2
100
200
500
1000
0.01
0.01
1
2 3
5
10 20
t, TIME OR PULSE WIDTH (ms)
50
Figure 10. Thermal Response
Motorola Bipolar Power Transistor Device Data
5
MOTOROLA [ MOTOROLA, INC ]
