4000Vpk isolation — where this part lives on the BOM
The TI ISO7221CHD is a dual-channel digital isolator using capacitive coupling, rated for 4000Vpk isolation in an 8-SOIC package. It's the sort of part you spec when a motor-drive control signal or a power-supply feedback loop needs to cross a safety barrier without pulling the whole board down. The 25Mbps data rate handles SPI, CAN, and RS-485 isolation cleanly — fast enough for most fieldbus and sensor links, but not a candidate for high-speed USB or gigabit Ethernet.
25kV/µs CMTI — why it matters in a switching environment
Common-mode transient immunity of 25kV/µs minimum means this isolator won't false-trigger when a SiC or IGBT switch transitions at several kV/µs. If you're isolating gate-drive feedback or phase-current sense in an inverter, that number is the difference between a clean signal and a glitch that trips the fault logic.
This part is sized for downhole drilling, engine-bay electronics, avionics, or any environment where the ambient can spike above 125°C. The 175°C ceiling is rare for a capacitive-coupling isolator — most peers top out at 125°C.
Propagation delay and pulse-width distortion — timing budget
Maximum propagation delay of 43ns in both directions and pulse-width distortion of 2ns max keep the timing predictable. For a 25Mbps link (40ns bit period), 43ns prop delay eats most of the budget — account for it in the SPI clock margin or CAN bit-timing calculation. The 1ns typical rise/fall edges are clean but fast enough to need careful PCB layout to avoid ringing.
Package and supply — what the board sees
8-SOIC narrow-body (3.90mm width), surface-mount. Supply range 3V to 5.5V — single-supply operation with unidirectional channels, so the input and output sides share the same VCC. No isolated power on chip; you provide the secondary-side rail externally. The 1/1 channel configuration (one channel each direction) suits a single bidirectional signal pair like UART TX/RX or SPI MOSI/MISO with a separate clock channel.
TI lists the ISO7221CHD as Active. The base product number ISO7221 covers a family of speed and temperature grades; the CHD suffix denotes the 25Mbps, -55°C to 175°C variant.