Device identity and channel assignment
The Skyworks SI8651BB-B-IU is a 5-channel general-purpose digital isolator using capacitive coupling to pass signals across a 2500 Vrms isolation barrier. The channel direction is fixed at 4 inputs on side 1 and 1 input on side 2 — unidirectional, so the data flow is hard-wired at the BOM level, not configurable. Rated for 150 Mbps, the part delivers a 13 ns max propagation delay in either direction, with 4 ns typical rise/fall times and a 4.5 ns max pulse-width distortion. That timing budget keeps the data eye open across the isolation gap for SPI, UART, and general-purpose logic links running at 50-100 MHz clock rates.
Isolation and transient immunity — what the ratings mean
The 2500 Vrms isolation rating is the basic insulation level per UL 1577 — it certifies the part for functional isolation in equipment where the working voltage stays under 300 Vrms. For reinforced isolation applications (motor drives, grid-tied inverters, medical equipment), a 5000 Vrms-rated sibling would be the correct choice. Common-mode transient immunity is specified at 50 kV/µs minimum. In a motor-drive or inverter environment where the IGBT switching edge couples a fast common-mode step across the barrier, a 50 kV/µs CMTI means the output does not glitch or lose data — the isolator rejects the transient rather than propagating it as a bit error.
Supply rails and temperature grade
The -40°C to 125°C operating temperature covers the industrial envelope — outdoor telecom cabinets, factory-floor PLC racks, and engine-bay electronics that see 105°C ambient still have margin.
Supplied in a 16-lead SSOP (3.90 mm body width) and also listed with the 16-QSOP supplier device package — these are the same footprint, same 0.635 mm pitch, same 4.4 mm body length.