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onsemi MOC3042SR2M — Optoisolators

MOC3042SR2M onsemi Optoisolator, Triac Output, 4170Vrms

MPNMOC3042SR2M
End of Life

onsemi MOC3042SR2M, 1-channel optoisolator with triac output, zero-crossing circuit, 4170Vrms isolation, 400 V off-state voltage, surface-mount 6-SMD gull wing package, UL approved.

$1.22Ref. price · indicative, final on quote
Packaging6-SMD, Gull Wing
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

MOC3042SR2M specifications
ParameterValue
Output typeTriac
MountingSurface Mount
Voltage - isolation4170Vrms
Voltage - off state400 V
Voltage - forward (Vf)1.25V
Current - hold400µA (Typ)
Current - DC forward (If)60 mA
Current - LED trigger (Ift)10mA
Operating temperature-40°C ~ 85°C
Approval agencyUL
PackageBulk
Case6-SMD, Gull Wing
Channels1
Static dV (dt)1kV/µs
Zero crossing circuitYes

Product details

Triac-output optoisolator with zero-crossing for AC load switching

The MOC3042SR2M is an onsemi optoisolator that integrates a triac output with a zero-crossing detection circuit, designed to switch AC loads such as solenoids, relays, motors, and lamps from a low-voltage control side. The zero-crossing circuit ensures the triac turns on only when the AC line voltage is near zero, which limits inrush current and reduces conducted EMI at the switching instant. This is a single-channel device in a 6-SMD gull wing package rated for surface-mount assembly.

Isolation and off-state voltage rating for mains applications

With a 4170Vrms isolation voltage and a 400 V off-state voltage rating, this part can reliably switch 240VAC loads with a healthy margin above the peak line voltage. The minimum static dV/dt of 1kV/µs provides immunity against false turn-on from fast line transients — a common concern when driving inductive loads like contactor coils or small motors. The typical LED trigger current (Ift) is 10 mA max, and the forward voltage is 1.25V typ, so a standard 5V or 3.3V logic output with a series resistor can drive the input LED.

Active production status and sourcing

The package option is Bulk, which is typical for engineering samples or small-run production.

Frequently asked questions

Does MOC3042SR2M have zero-crossing detection?

Yes. The datasheet specifies a zero-crossing circuit, meaning the internal triac triggers only when the AC line voltage is near zero. This reduces inrush current and EMI compared to random-phase optoisolators.

Can MOC3042SR2M be used to drive a 240VAC load?

Yes. The off-state voltage rating is 400 V, which exceeds the peak of a 240VAC line (approximately 340 V peak). The 4170Vrms isolation provides reinforced insulation between the control and load sides. For inductive loads, an external snubber (RC network) across the triac is recommended to suppress dV/dt transients beyond the 1kV/µs minimum rating.

What is the closest pin-compatible alternative to MOC3042SR2M in this Optoisolators family?

The MOC3041 is a common peer in the same family, but it has a higher LED trigger current (15 mA max vs 10 mA max for the MOC3042). Both are 6-pin DIP/gull wing packages with the same pinout and 400 V off-state rating. The MOC3042 offers a lower trigger threshold, which can simplify the drive circuit with lower-current logic outputs. Confirm the trigger current requirement for your specific design before substituting.