What this isolator brings to the board
The Texas Instruments ISO7731DBQR is a three-channel, unidirectional digital isolator using capacitive coupling to pass signals across a 3000 Vrms isolation barrier at up to 100 Mbps. The 85 kV/µs common-mode transient immunity (CMTI) means it stays reliable in motor-drive or inverter environments where fast voltage swings on the isolated side would otherwise corrupt data.
Channel count and direction — what the 2/1 split buys you
Three unidirectional channels are configured as two on side 1 and one on side 2. That 2/1 split maps cleanly to a typical SPI bus: SCLK and MOSI forward, MISO reverse. For a half-duplex RS-485 or CAN interface, the single reverse channel handles the receive path while the two forward channels carry control and data. The unidirectional architecture also keeps propagation delay symmetric — 16 ns max in both directions — so timing closure on the bus is straightforward.
That puts it in play for avionics, satellite payloads, downhole instrumentation, and outdoor telecom cabinets where the ambient can swing from a cold soak to a hot day under full sun.
Lifecycle and sourcing
For dual-sourcing or supply resilience, the base product number ISO7731 family includes other channel-count and package variants — the ISO7731DWR is the wider-body SOIC-16 version if you need more creepage distance.