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onsemi FOD4208SD — Optoisolators

FOD4208SD Optoisolator Triac Output 5kVrms 800V off-state

MPNFOD4208SD
End of Life

onsemi FOD4208SD, Optoisolator with Triac output, 1 channel, 5000 Vrms isolation, 800 V off-state, 60 µs turn-on, 10 kV/µs static dV/dt, surface mount 6-SMD gull wing package.

$4.61Ref. price · indicative, final on quote
onsemi FOD4208SD datasheet (PDF)
Packaging6-SMD, Gull Wing
RoHSROHS3 Compliant
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

FOD4208SD specifications
ParameterValue
Output typeTriac
MountingSurface Mount
Voltage - isolation5000Vrms
Voltage - off state800 V
Voltage - forward (Vf)1.28V
Current - hold500µA
Current - DC forward (If)30 mA
Current - LED trigger (Ift)2mA
Operating temperature-55°C ~ 100°C
Approval agencycUL, FIMKO, UL
PackageTape & Reel (TR); Cut Tape (CT)
Turn on time60µs
Case6-SMD, Gull Wing
Channels1
Static dV (dt)10kV/µs
Zero crossing circuitNo

Product details

Triac output optoisolator for line-voltage switching

The FOD4208SD is an onsemi optoisolator with a Triac output, rated for 5000 Vrms isolation and 800 V off-state blocking, making it suitable for switching 240 VAC or 480 VAC loads with transient margin. With a 60 µs turn-on time and no zero-crossing circuit, it fires at any point in the AC cycle, enabling phase-angle dimming, soft-start, or random-fire control in industrial and appliance applications. The single-channel device comes in a 6-SMD gull-wing package for surface-mount reflow assembly, with approvals from cUL, FIMKO, and UL.

Parametric deep-dive: drive current, dV/dt, and temperature

Static dV/dt is a minimum of 10 kV/µs, providing immunity against fast voltage transients common in motor-drive, relay-coil, and solenoid circuits that could otherwise false-trigger a standard triac driver. Hold current is 500 µA typical, and forward voltage is 1.28 V typical at 30 mA maximum DC forward current, defining the LED drive budget.

Frequently asked questions

Is FOD4208SD a zero-crossing optoisolator?

No, it has no zero-crossing circuit, so the triac output fires at any point in the AC cycle, enabling phase-angle control or random-fire switching.

Can FOD4208SD be used to drive a triac directly?

The FOD4208SD itself contains a Triac output and can directly drive a load up to 800 V off-state. For higher current, it can drive an external power triac gate; the 2 mA LED trigger current and 500 µA hold current are compatible with standard triac gate drive requirements.