4170Vrms isolation in a 6-SMD gull-wing package
The onsemi 4N26SR2VM is a single-channel optocoupler with a DC-input LED and a phototransistor output that includes a base connection. The 4170Vrms isolation rating means it provides reinforced galvanic isolation between the logic-side and load-side circuits — enough to protect a 240VAC control interface from transient spikes without an external isolator. The 6-SMD gull-wing footprint fits standard pick-and-place reflow assembly. The base pin on the output side lets you bias the transistor for faster switching or configure it as a photodarlington with an external transistor — a flexibility not available on base-less optocouplers.
Switching speed and transfer ratio — the real BOM-fit numbers
Minimum current transfer ratio is 20% at 10 mA forward current. Turn-on and turn-off times are both 2 µs typical. This 2 µs propagation delay sets the maximum data rate at roughly 250 kbps in a saturated-switching application — fine for 50/60 Hz line monitoring, relay drivers, or isolated serial interfaces, but too slow for high-speed SPI or CAN. The output transistor is rated for 30 V maximum collector-emitter voltage and 500 mV saturation voltage at rated drive. The 30 V ceiling limits the load-side supply to 24 V rails with margin; the low Vce(sat) keeps power dissipation down in the output stage.
onsemi has marked the 4N26SR2VM as obsolete. No official successor part number is listed by the manufacturer. Tape-and-reel packaging (TR suffix) means the part is supplied on 13-inch reels for automated assembly. The 6-SMD gull-wing leads are solderable with standard SnAgCu reflow profiles — no special bake-out required for MSL 1 parts, but verify the moisture sensitivity level on the reel label before the oven.