Quad-channel digital isolator for noisy industrial buses
The Texas Instruments ISO7741DBQ is a quad-channel, general-purpose digital isolator using capacitive coupling to transfer digital signals across an isolation barrier rated at 2500 Vrms. It is designed for applications where galvanic isolation is required between communication interfaces — think isolated SPI, UART, RS-485, or CAN buses in motor drives, grid-tied inverters, PLC I/O modules, and medical equipment. The 4-channel unidirectional configuration (3 channels on side 1, 1 channel on side 2) suits the typical data/clock/select plus one feedback signal arrangement.
100 Mbps data rate — timing budget for SPI and UART
At 100 Mbps the ISO7741DBQ handles 50 MHz SPI clocks cleanly, with a typical propagation delay of 16 ns and pulse-width distortion held to 4.9 ns max. The 2.4 ns rise/fall times keep the eye open across a short backplane trace, but the fast edges also mean you want to keep the output trace short or add a small series resistor to damp ringing — especially if the load is a high-impedance CMOS input on the other side of the barrier.
85 kV/µs CMTI — surviving the switching node
The 85 kV/µs minimum common-mode transient immunity is the spec that matters when this isolator sits between a controller and a half-bridge gate driver. Fast SiC or GaN switching edges can inject several kV/µs across the barrier; if the isolator's CMTI is too low, the output glitches and the power stage sees a spurious on/off command. At 85 kV/µs this part has margin for most IGBT and SiC designs up to the 10-20 kV/µs range that appears in hard-switched converters.
Supply range and dual-voltage operation
The supply range spans 2.25 V to 5.5 V on both sides, which means you can run the input side at 3.3 V and the output side at 5.0 V without a level shifter — useful when isolating a 3.3 V MCU from a 5 V peripheral bus. The part does not include an integrated DC-DC converter, so each side needs its own isolated power rail (e.g., a transformer-coupled push-pull or an isolated module).
Lifecycle and sourcing posture
For production BOMs this is a low-risk line item — no urgency to qualify a drop-in replacement.