Triac output for random-phase AC switching
The onsemi MOC3021VM is a single-channel optoisolator with a Triac output in a 6-DIP through-hole package. It provides 4170 Vrms isolation between the LED input and the Triac output, rated for 400 V off-state voltage — sufficient for switching 240 VAC loads directly from a logic-level signal. With no zero-crossing circuit, the Triac fires at any point in the AC cycle on receipt of the LED trigger current. This random-phase turn-on is essential for phase-angle control applications like resistive heater regulation or incandescent lamp dimming, where the load must be switched on mid-cycle. The hold current of 100 µA (typical) keeps the Triac latched once triggered, so the LED can be de-energized after turn-on to reduce driver power.
Industrial temperature range and approvals
The part carries IEC/EN/DIN and UL approvals — these are the safety-agency certifications required for equipment sold into European and North American markets. The 4170 Vrms isolation rating satisfies reinforced-insulation requirements for mains-connected circuits per IEC 60950 and UL 1577.
Package and board-fit for through-hole assembly
The through-hole leads provide a robust mechanical anchor on the PCB, preferred over surface-mount in high-vibration environments or when the board sees repeated thermal cycling. Supplied in Tube packaging — each tube holds a fixed quantity of devices for manual or automated insertion. The 6-DIP supplier device package code matches the case outline; no additional footprint adaptation is needed beyond the standard DIP-6 land pattern.
Sourcing and cross-reference considerations
When sourcing the MOC3021VM, the closest functional peer in the same package is the MOC3073M. Both are through-hole 6-DIP, single-channel Triac optoisolators with 4170 Vrms isolation and no zero-crossing. The MOC3073M specifies a static dv/dt of 1 kV/µs, which is higher than the MOC3021VM's unspecified but typically lower dv/dt rating — meaning the MOC3073M is more immune to false triggering on fast mains transients. For a direct drop-in without rewiring, the MOC3021VM fits the same footprint and pinout.