MOC3051 Datasheet, PDF (5/8 Pages) Motorola, Inc – 6-Pin DIP Random-Phase Optoisolators Triac Drivers

TYPICAL ELECTRICAL CHARACTERISTICS
MOC3051 MOC3052
TA = 25°C
100
10
t(d)
1
t(f)
0.1
10
20
30
40
50
60
IFT, LED TRIGGER CURRENT (mA)
Figure 9. Delay Time, t(d), and Fall Time, t(f),
versus LED Trigger Current
t(delay), t(f) versus IFT
The triac driver’s turn on switching speed consists of a turn
on delay time t(d) and a fall time t(f). Figure 9 shows that the
delay time depends on the LED trigger current, while the ac-
tual trigger transition time t(f) stays constant with about one
micro second.
The delay time is important in very short pulsed operation
because it demands a higher trigger current at very short trig-
ger pulses. This dependency is shown in the graph IFT ver-
sus LED PW.
The turn on transition time t(f) combined with the power
triac’s turn on time is important to the power dissipation of
this device.
Switching Time Test Circuit
SCOPE
IFT
VTM
t(d)
t(f)
ZERO CROSS
DETECTOR
EXT. SYNC
FUNCTION
GENERATOR
Vout
115 VAC
PHASE CTRL.
PW CTRL.
PERIOD CTRL.
Vo AMPL. CTRL.
ISOL. TRANSF.
VTM
IFT
10 kΩ
DUT
AC
100 Ω
+400
Vdc
PULSE
INPUT
RTEST
MERCURY
WETTED
RELAY
APPLIED VOLTAGE
WAVEFORM
0 VOLTS
252 V
τ_RC
CTEST
D.U.T.
R = 1 kΩ
1. The mercury wetted relay provides a high speed repeated
pulse to the D.U.T.
2. 100x scope probes are used, to allow high speeds and
X100
voltages.
SCOPE
3. The worst–case condition for static dv/dt is established by
PROBE
triggering the D.U.T. with a normal LED input current, then
removing the current. The variable RTEST allows the dv/dt to
be gradually increased until the D.U.T. continues to trigger in
response to the applied voltage pulse, even after the LED
current has been removed. The dv/dt is then decreased until
Vmax = 400 V
the D.U.T. stops triggering. τ_RC is measured at this point and
recorded.
dv/dt =
0.63 Vmax
τ_RC
=
252
τ_RC
Figure 10. Static dv/dt Test Circuit
Motorola Optoelectronics Device Data
5