50 Mbps capacitive-coupled isolator in 8-SOIC
The Texas Instruments ISO7421FEDR is a general-purpose digital isolator using capacitive coupling to transfer logic signals across a 2500 Vrms isolation barrier. It provides two unidirectional channels with one input on side 1 and one on side 2, making it a straightforward fit for isolating a single TX and RX line in SPI, UART, or GPIO isolation. The 50 Mbps data rate handles most industrial serial buses without timing margin concerns, and the 11 ns max propagation delay keeps the signal path tight for feedback loops.
CMTI and signal integrity
Common-mode transient immunity is rated at 25 kV/µs minimum, which is sufficient for most motor-drive and inverter applications where fast switching edges couple common-mode noise across the barrier. The 1.8 ns typical rise and 1.7 ns fall times keep the output edges clean, and the 3.7 ns max pulse-width distortion means the duty cycle stays close to 50% — important for PWM isolation where pulse symmetry matters.