Three-channel capacitive isolator for harsh industrial environments
The Texas Instruments ISO7731FDBQR is a three-channel, unidirectional digital isolator using capacitive coupling technology to provide galvanic isolation up to 3000Vrms. It is designed for general-purpose signal isolation in industrial automation, motor drives, power supplies, and isolated communication interfaces where noise immunity and signal integrity across the barrier are critical. With a 100Mbps data rate, 16ns max propagation delay, and 1.3ns/1.4ns typical rise/fall times, this part handles high-speed digital signals like SPI, UART, and PWM without introducing significant timing skew or jitter. The wide supply range from 2.25V to 5.5V on both sides allows direct interface with 3.3V and 5V logic families without external level translation, simplifying the power architecture.
85 kV/µs CMTI — why it matters for motor drives and inverters
The minimum common-mode transient immunity of 85kV/µs is the standout parameter for applications with fast-switching power stages. In a motor drive or DC-DC converter, the switching node can slew at tens of kV/µs. A lower CMTI isolator would let that transient couple across the barrier as a data error or latch-up. The ISO7731FDBQR's 85kV/µs floor keeps the output state valid through those edges, which is the difference between a clean feedback loop and a faulted gate driver.
No separate high-rel screening step is needed for the temperature grade itself.
Channel assignment: 2 inputs on Side 1, 1 input on Side 2
The three unidirectional channels are split as two inputs on Side 1 and one input on Side 2. This 2/1 configuration maps directly to common SPI isolation: two forward channels for SCLK and MOSI (or CS), and one reverse channel for MISO. For UART isolation, the two forward channels can carry TX and a control signal, with the reverse channel for RX. The unidirectional nature means no bidirectional data lines — plan your signal direction accordingly.
Package and footprint: 16-SSOP with 3.90mm body width
Housed in a 16-pin SSOP package with a 3.90mm body width and 0.154" pitch, the ISO7731FDBQR occupies a compact footprint suitable for space-constrained multi-channel isolation on a single board. The surface-mount package is compatible with standard reflow soldering processes.