What this 7.5 kV opto brings to a board
The onsemi MCT2ESM is a single-channel optoisolator in a 6-SMD gull wing package — the kind you reach for when you need to pass a DC logic signal across a 7500Vpk isolation barrier without ground loops or common-mode noise coupling. Its transistor-with-base output gives you access to the base node, so you can bias the phototransistor for faster switching or lower saturation — useful when the downstream logic input needs a clean edge and you are not running the output rail at the full 30 V ceiling.
Ratings that decide the fit
Minimum current transfer ratio of 20 % at 10 mA forward current means the output transistor saturates with 2 mA of collector drive — enough to pull a TTL or CMOS input low, but you need to check the CTR margin at the actual LED drive current your design delivers. The 7500Vpk isolation voltage is the headline number for this part — it is the peak repetitive voltage the internal photodiode gap can withstand, not a continuous rating. In a motor-drive or industrial-PLC application with 600 VDC bus transients, that margin keeps the creepage safe across the SMD package. Switching is rated at 2 µs typical turn-on and 2 µs turn-off — fast enough for 100 kHz serial data or a PWM gate signal, but the rise time (2 µs) and fall time (1.5 µs) add skew that matters if you are timing a synchronous rectifier or a dead-time window. Output can sink 50 mA continuous at up to 30 V, with Vce saturation clamped at 400 mV max — the transistor drops under half a volt when fully on, so the output rail stays clean even at the current limit. Forward voltage is 1.25 V typical at 10 mA, and the absolute max LED current is 60 mA — the LED is the wear item; stay below 20 mA for long-term reliability in a 100 °C ambient.
Listed as active with ROHS3 compliance — this is a current-production part from onsemi, not an end-of-life scavenge.
How it stacks against 4N25SR2M
The closest functional peer is the 4N25SR2M — same DC input, same transistor-with-base output, same surface-mount package family. The MCT2ESM delivers a higher isolation voltage (7500Vpk vs 4170Vrms) and lower Vce saturation (400 mV vs 500 mV), but the 4N25SR2M is available in tape-and-reel if your pick-and-place line prefers reel feed over tube.