Quad phototransistor optocoupler in 16-SOIC
The Vishay TCMT4606 is a 4-channel phototransistor optocoupler in a 16-SOIC package, providing 3750Vrms galvanic isolation between input and output. Each channel can handle up to 50mA output current and 70V across the transistor, making it suitable for logic-level interfacing, PLC I/O modules, and industrial sensor isolation where board space is tight — four channels in one SOIC footprint instead of four separate DIP-4 parts.
CTR range and drive margin
The current transfer ratio spans 100% to 300% at a forward current of 5mA. That means with 5mA into the LED, the output transistor can sink between 5mA and 15mA — enough to drive a CMOS logic input or a small relay coil directly. The wide CTR spread (3:1) is typical for phototransistor couplers; design the pull-up resistor for the minimum CTR to guarantee logic-level switching across all temperature and aging conditions.
Switching speed and timing budget
Rise and fall times are 3µs and 4.7µs typical; turn-on and turn-off times are 6µs and 5µs typical. This part is not for high-speed isolation — expect usable bandwidth around 10–20 kHz. For 100 kHz+ isolated data, look at a digital isolator or high-speed optocoupler. But for 50/60 Hz mains sensing, relay drive, or slow digital signals, the TCMT4606 is perfectly adequate and avoids the cost of faster parts.
AC/DC input flexibility
The input stage accepts both AC and DC drive. With AC input, the LED conducts on both half-cycles, which is useful for zero-crossing detection or line-voltage monitoring without external rectification. For DC logic, a series resistor sets the forward current to 5–60 mA (max 60 mA absolute). Typical forward voltage is 1.35V at 5mA, compatible with 3.3V and 5V logic families.
Temperature range and environment
It does not reach the 125°C required for automotive under-hood or downhole applications. The 16-SOP (SOIC-16) body is 4.40mm wide, surface-mount, and MSL 1 (moisture sensitivity level per the datasheet), so no bake step before reflow if the bag seal is intact.
Lifecycle and sourcing
It is ROHS3 compliant. No known pin-compatible second source from another manufacturer, but the TCMT4603 (same package, different CTR bin) is a functional alternative within the same family if the CTR range can be adjusted.