ISO7421DR

The ISO7421DR from Texas Instruments is a dual-channel digital isolator with one forward and one reverse channel in a narrow-body 8-SOIC package. Using capacitive coupling through a silicon dioxide (SiO2) insulation barrier, it provides 2500Vrms galvanic isolation for one minute per UL1577 and 4242Vpk per VDE 0884-10. The device supports data rates up to 1Mbps with 9ns typical propagation delay. It operates from 3.3V or 5V supplies on either side, enabling level translation across the isolation barrier. Typical current consumption is 1.5mA per channel at 3.3V.

The ISO7421DR uses capacitive coupling through an SiO2 insulation barrier to transmit digital signals across the isolation boundary. Each channel consists of a logic input buffer, a high-voltage capacitive coupling element, and a logic output buffer. The input signal modulates a carrier that passes through the isolation capacitor and is demodulated on the output side. The reverse channel operates identically in the opposite direction. The SiO2 barrier provides galvanic isolation while maintaining signal integrity with low propagation delay (9ns typical) and low skew (300ps typical). Common-mode transients are rejected by the differential capacitive coupling structure.

• RS-485/RS-232 communication isolation barrier
• SPI and I2C bus isolation in industrial systems
• Motor drive gate driver signal isolation
• Medical equipment patient-side isolation
• Isolated power supply feedback loops