4 Motorola Bipolar Power Transistor Device Data
Table 1. Test Conditions for Dynamic Performance
VCEO(sus) VCEX AND INDUCTIVE SWITCHING RESISTIVE SWITCHING
INPUT
CONDITIONS
CIRCUIT
VALUES
TEST CIRCUITS
20
Ω
1
0
PW Varied to Attain
IC = 100 mA
Lcoil = 10 mH, VCC = 10 V
Rcoil = 0.7 Ω
Vclamp = VCEO(sus)
Lcoil = 180 µH
Rcoil = 0.05 Ω
VCC = 20 V
VCC = 250 V
RL = 12.5 Ω
Pulse Width = 25 µs
INDUCTIVE TEST CIRCUIT
TURN–ON TIME
IB1 adjusted to
obtain the forced
hFE desired
TURN–OFF TIME
Use inductive switching
driver as the input to
the resistive test circuit.
t1 Adjusted to
Obtain IC
Test Equipment
Scope — Tektronix
475 or Equivalent
RESISTIVE TEST CIRCUITOUTPUT WAVEFORMS
2
IB1
1
2
5 V
INDUCTIVE TEST CIRCUIT
1
INPUT
2
Rcoil
Lcoil
VCC
Vclamp
RS =
0.1
Ω
1N4937
OR
EQUIVALENT
TUT
SEE ABOVE FOR
DETAILED CONDITIONS
1
INPUT
2
Rcoil
Lcoil
VCC
Vclamp
RS =
0.1
Ω
1N4937
OR
EQUIVALENT
TUT
SEE ABOVE FOR
DETAILED CONDITIONS
t1
IC(pk) tf Clamped
tft
t
t2
TIME
VCE or
Vclamp
1
2
TUT
RL
VCC
t1 ≈Lcoil (ICpk)
VCC
t2 ≈Lcoil (ICpk)
VClamp
*Adjust –V such that VBE(off) = 5 V except as required for RBSOA (Figure 8).
Figure 6. Inductive Switching Measurements
trv
TIME
IC
VCE 90% IB1
tsv
IC pk Vclamp
90% Vclamp 90% IC
10% Vclamp 10%
IC pk 2% IC
IB
tfi tti
tc
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
ā
–
ā
90% Vclamp
tfi = Current Fall Time, 90
ā
–
ā
10% IC
tti = Current Tail, 10
ā
–
ā
2% IC
tc = Crossover Time, 10% Vclamp to 10% IC
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 VCC IC (tc) f
In general, t rv + tfi
^
tc. However, at lower test currents
this relationship may not be valid.
As is common with most switching transistors, resistive
switching is specified and has become a benchmark for de-
signers. However, for designers of high frequency converter
circuits, the user oriented specifications which make this a
“SWITCHMODE” transistor are the inductive switching
speeds (tc and tsv) which are guaranteed.