MOC3051 MOC3052

5

Motorola Optoelectronics Device Data

TYPICAL ELECTRICAL CHARACTERISTICS

TA = 25°C

Figure 9. Delay Time, t(d), and Fall Time, t(f),

versus LED Trigger Current

IFT, LED TRIGGER CURRENT (mA)

100

0.1

10

20

30

40

50

60

10

1

t(f)

t(d)

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

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

voltages.

3. The worst–case condition for static dv/dt is established by

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

the D.U.T. stops triggering.

τRC is measured at this point and

recorded.

Figure 10. Static dv/dt Test Circuit

+400

Vdc

PULSE

INPUT

RTEST

CTEST

R = 1 k

Ω

MERCURY

WETTED

RELAY

D.U.T.

X100

SCOPE

PROBE

APPLIED VOLTAGE

WAVEFORM

Vmax = 400 V

dv/dt =

0.63 Vmax

τRC

252

τRC

=

τRC

252 V

0 VOLTS

SCOPE

IFT

VTM

t(d)

t(f)

ZERO CROSS

DETECTOR

EXT. SYNC

Vout

FUNCTION

GENERATOR

PHASE CTRL.

PW CTRL.

PERIOD CTRL.

Vo AMPL. CTRL.

IFT

VTM

10 k

Ω

DUT

100

Ω

ISOL. TRANSF.

AC

115 VAC