Capacitive-coupled isolation for 100 Mbps digital links
The Texas Instruments ISO7741FDBQR is a 4-channel, unidirectional, general-purpose digital isolator using capacitive-coupling technology. It is designed to pass digital signals across a galvanic isolation barrier rated at 3000 Vrms, with a data rate up to 100 Mbps. Typical applications include industrial fieldbus isolation (RS-485, CAN), SPI isolation, general-purpose digital I/O isolation, and isolated power-supply feedback loops where high common-mode transient immunity (85 kV/µs minimum) is needed to survive fast-switching power stages.
Channel assignment and signal direction
The ISO7741FDBQR has three channels on side 1 and one channel on side 2 (3/1 configuration), all unidirectional. This suits common isolation topologies like SPI, where SCLK, MOSI, and chip-select run from the controller to the peripheral (side 1 to side 2), and MISO returns the other direction (side 2 to side 1). The 2.4 ns typical rise/fall time and 16 ns maximum propagation delay keep timing margins tight enough for 100 Mbps clocked interfaces.
The wide supply range also helps when the rail droops under cold-crank conditions.
Package and footprint
The narrow SSOP footprint is common on mixed-signal boards where board area is at a premium. No isolated power is integrated — the part requires separate isolated supplies on each side.