Triac driver for non-zero-crossing AC loads
The MOC3012M is a 1-channel optoisolated triac driver from onsemi in a 6-DIP through-hole package. Its 4170Vrms isolation rating provides a reinforced safety barrier between low-voltage control logic and line-voltage AC loads, with 250 V off-state capability. The part has no zero-crossing circuit, meaning the output triac can be triggered at any phase angle. This is essential for phase-control dimming, soft-start, or any application where the load must turn on mid-cycle rather than at the voltage zero crossing.
LED drive and output characteristics
The LED trigger current (Ift) is 5mA maximum, which allows direct drive from a 5 V logic output through a series resistor without an external transistor buffer. Typical forward voltage (Vf) is 1.15V, and the LED can handle up to 60 mA continuous forward current. The output triac has a typical holding current (Ih) of 100 µA. This low holding current helps the triac stay latched on with lightly inductive or low-current loads, reducing the risk of premature turn-off at the load current zero crossing.
Lifecycle and sourcing reality
For surface-mount designs, the MOC3011SM offers the same 4170Vrms isolation and non-zero-crossing triac output in an SMT package. For a higher static dv/dt rating (1 kV/µs), the MOC3073M is a through-hole alternative within the same family.