15 Mbps isolation that holds the bus
The Renesas NEPOC PS9121-V-F3-AX is a single-channel optocoupler with an open-collector output, designed for galvanic isolation in industrial communication links. It switches at 15Mbps — fast enough for standard fieldbus interfaces like RS-485 and CAN isolators, or for isolating encoder and PLC I/O signals. The 3750Vrms isolation rating provides basic insulation for equipment operating in 250 Vrms mains environments, typical for motor drives, servo controllers, and industrial power supplies.
Open collector output — flexible level translation
The open collector output lets you pull up to a different supply voltage than the input side, which is useful when the controller runs at 3.3 V but the receiving logic is 5 V tolerant. Rise and fall times are 20 ns and 5 ns typical, keeping the pulse shape clean at 15 Mbps. Propagation delay is symmetrical at 75 ns max for both low-to-high and high-to-low transitions, which simplifies timing budget calculations in half-duplex links.
Common-mode transient immunity for noisy environments
Rated at 15 kV/µs minimum common-mode transient immunity, the PS9121-V-F3-AX can reject fast voltage transients that couple across the isolation barrier in motor-drive or inverter applications. This rating is measured with the output loaded at 25 mA and the supply at 3.3 V — a realistic condition for industrial gate drives and power-stage feedback. If your system sees higher dV/dt from SiC or GaN switching edges, the RV1S9161 peer offers 100 kV/µs, but for IGBT-based drives below 20 kHz this part's margin is adequate.
The input forward voltage is 1.65 V typical, compatible with 3.3 V logic outputs driving the LED through a series resistor sized for 30 mA max.
Package and footprint
Housed in a 5-pin 6-SOIC package with 4.40 mm body width, it shares the same footprint as the standard SOIC-5 optocoupler layout. Surface-mount assembly is standard for reflow soldering; the part is ROHS3 compliant.
Active lifecycle with no immediate end-of-life risk
For a BOM line requiring a 15 Mbps open-collector optocoupler with 3750 Vrms isolation, this part can be qualified for production without an imminent second-sourcing push — though a forward-looking design review should confirm the 5-SO package remains available across the product's expected life.