Datasheet

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Document Number: 83690
196 Rev. 1.5, 07-May-08
BRT21/BRT22/BRT23
Vishay Semiconductors
Optocoupler, Phototriac Output,
Zero Crossing
Note
As per IEC 60747-5-2, § 7.4.3.8.1, this optocoupler is suitable for "safe electrical insulation" only within the safety ratings. Compliance with the
safety ratings shall be ensured by means of protective circuits.
POWER FACTOR CONSIDERATIONS
A snubber is not needed to eliminate false operation of the
TRIAC driver because of the high static and commutating
dV/dt with loads between 1.0 and 0.8 power factors. When
inductive loads with power factors less than 0.8 are being
driven, include a RC snubber or a single capacitor directly
across the device to damp the peak commutating dV/dt
spike. Normally a commutating dV/dt causes a turning-off
device to stay on due to the stored energy remaining in the
turning-off device.
But in the case of a zero voltage crossing optotriac, the
commutating dV/dt spikes can inhibit one half of the TRIAC
from turning on. If the spike potential exceeds the inhibit
voltage of the zero cross detection circuit, half of the TRIAC
will be heldoff and not turn-on. This hold-off condition can be
eliminated by using a snubber or capacitor placed directly
across the optotriac as shown in Figure 1. Note that the value
of the capacitor increases as a function of the load current.
The hold-off condition also can be eliminated by providing a
higher level of LED drive current. The higher LED drive
provides a larger photocurrent which causes the
phototransistor to turn-on before the commutating spike has
activated the zero cross network. Figure 2 shows the
relationship of the LED drive for power factors of less than
1.0. The curve shows that if a device requires 1.5 mA for a
resistive load, then 1.8 times 2.7 mA) that amount would be
required to control an inductive load whose power factor is
less than 0.3.
Fig. 1 - Shunt Capacitance vs. Load Current
SAFETY AND INSULATION RATINGS
PARAMETER TEST CONDITION SYMBOL MIN. TYP. MAX. UNIT
Climatic classification
(according to IEC 68 part 1)
40/100/21
Comparative tracking index CTI 175 399
V
IOTM
6000 V
V
IORM
630 V
P
SO
200 mW
I
SI
400 mA
T
SI
175 °C
Creepage distance standard DIP-6 7 mm
Clearance distance standard DIP-6 7 mm
Creepage distance 400 mil DIP-6 8 mm
Clearance distance 400 mil DIP-6 8 mm
iil410_01
400350300250200150100500
0.001
0.01
0.1
1
I
L
- Load Current (mA) (RMS)
C
s
- Shunt Capacitance (µF)
C
s
(µF) = 0.0032 (µF)*10^0.0066 I
L
(mA)
T
a
= 25 °C, PF = 0.3
I
F
= 2.0 mA