150 Mbps capacitive-coupled isolator for industrial signal paths
The Texas Instruments ISO7221MDRG4 is a 2-channel, unidirectional digital isolator using capacitive coupling technology, rated for 150 Mbps data rate and 2500 Vrms isolation voltage.
Propagation delay and pulse-width distortion — timing closure for the isolation barrier
Maximum propagation delay is 16 ns in both directions (tpLH / tpHL), and pulse-width distortion is held to 1 ns maximum. For an engineer budgeting timing margin across an isolated SPI or parallel bus, the symmetrical 16 ns delay means the part adds about one gate-delay equivalent per edge; the 1 ns PWD ensures duty-cycle integrity for clock signals up to 150 Mbps. The rise and fall times are 1 ns typical, which keeps edge rates fast enough for high-speed signalling while remaining within the capacitive coupling channel's capability. At 150 Mbps the part handles a 6.67 ns bit period, so the 16 ns propagation delay occupies roughly 2.4 bit periods — something to account for when closing timing on a loop that crosses the isolation boundary twice.
Common-mode transient immunity — staying alive through a motor-drive commutation event
In a variable-frequency drive or inverter leg, the switching node can slew at 10–20 kV/µs; this part's floor of 25 kV/µs provides margin so the output doesn't glitch when the ground plane jumps. For a PCB layout engineer, that means the isolation barrier holds even with fast IGBT or SiC switching edges coupling through parasitic capacitance.