What is The Snubberless TRIAC Drive Optocouplers:
The Snubberless TRIAC Drive Optocouplers feature a built-in active dv/dt clamp providing best-in-class noise immunity (dv/dt) of 10,000V/μs, which is superior to the average dv/dt rating (1,500V/μs) of monolithic TRIAC drivers. This superior performance eliminates the RC snubber network required for lower dv/dt-rated monolithic opto TRIAC drivers. This saves valuable design time and reduces bill of materials (BOMs). High noise immunity makes these products ideal for noisy industrial environments as they offer a more robust solution for isolating solid-state relays, AC motor controls and lighting ballasts. 

Why We Need The Snubberless TRIAC Drive Optocouplers:
Reduce Component Count: Due to the FOD4xx’s high commutating and static dv/dt immunity (10kV/us minimum), its performance is such that additional noise filtering is not required. This allows the snubber across the TRIAC driver to be eliminated from the circuit. Since the snubber capacitor is across the mains, it must be safety certified. These special safety certified capacitors are very expensive, approximately $0.35 each in high volume! Those capacitors are also about four times the size of the optocoupler which makes removing them a significant space savings!



Reducing Standby Power: By eliminating the snubber network a significant reduction in standby power consumption can be realized. The snubber circuit consumes power even when the load is in the off-state. As an example, a 240V AC Mains application using a 0.1uF snubber capacitor conducts 10mA in the off-state translating to a power loss of 2W. With new directives for reducing standby power as energy costs skyrocket, the power savings offered by these devices can substantially help designers achieve their standby power targets.

Ease of Design: Aside from the cost savings of removing the RC snubber components, there’s another advantage. Selecting the values of the RC network is tedious. Often, designers don’t know the power factor of their load, what noise will come from the mains, the type of load being switched, or even what type of load will be connected to the circuit (e.g., in the case of hockey puck solid state relays). As a result, they are forced to estimate the values and then hand tune the circuit on the bench. For the case of the SSR, that’s impossible because they can’t simulate an undefined load. The FOD4xx eliminates this hassle by removing those components from the circuit.

Note: This optoisolator should not be used to drive a load directly. It is intended to be a discrete triac driver device only.