Bidirectional I²C isolator with capacitive coupling
The Texas Instruments ISO1540D is a bidirectional, capacitive-coupling I²C isolator that provides galvanic isolation of up to 2500Vrms across two channels.
The 2500Vrms isolation rating is the working voltage the device can withstand between the two sides; it is the number that determines whether this part meets the reinforced-insulation requirement in medical (IEC 60601) or industrial (IEC 61010) equipment. In a motor-drive or inverter design where the switching node slews at tens of kV/µs, a CMTI below 25kV/µs can cause data corruption or latch-up. This part's CMTI rating is sized for those environments.
Package and supply — design-in checklist
The ISO1540D comes in an 8-SOIC package (3.90 mm width, 0.154" body), surface-mount only. The supply range of 3V to 5.5V on each side means you can run one side at 3.3V and the other at 5V without a level shifter — common when bridging a 3.3V MCU to a 5V sensor bus. No isolated power supply is integrated; each side needs its own local rail. The bidirectional channel type handles both SDA and SCL on a single pair of pins, so no external direction control is needed.
For dual-sourcing resilience, the ISO1540 (without the D suffix) is the same base device in a different shipping tube or tape configuration — functionally identical, same isolation and data rate ratings, same SOIC-8 footprint. Qualifying both variants gives you a second supply path without a board spin.