ISO7841FDWR

The ISO7841FDWR is Texas Instruments’ high-performance quad-channel reinforced digital isolator from the ISO7841 family, delivering 8000Vpeak and 5700Vrms isolation ratings with a silicon-dioxide (SiO2) capacitive barrier. The ‘F’ suffix denotes a default-low output state when input power or signal is lost, critical for fail-safe system design. With three forward and one reverse channel, it supports bidirectional communication across the isolation boundary. The device achieves industry-leading common-mode transient immunity (CMTI) of ±100kV/µs minimum, making it highly robust in noisy industrial environments. It supports data rates up to 100Mbps with only 11ns typical propagation delay. Both supply rails accept 2.25V to 5.5V, enabling voltage-level translation across the isolation barrier. Comprehensive safety certifications include VDE 0884-17, UL 1577, CSA, CQC, and TUV.

Capacitive Isolation Barrier

The ISO7841FDWR uses high-voltage silicon-dioxide (SiO2) capacitors as the isolation barrier between input and output sides. Digital signals are modulated into high-frequency carrier waveforms, transmitted across the capacitive barrier, and demodulated on the receiving side. This capacitive coupling approach provides excellent electromagnetic immunity and low emissions compared to optocoupler or inductive alternatives.

Signal Path Architecture

Each channel consists of an input buffer, modulator, high-voltage SiO2 capacitor pair, demodulator, and output buffer. The modulator encodes the input logic state into a differential carrier signal that passes through the isolation capacitors. On the receive side, the differential signal is demodulated and restored to the original logic level. The carrier frequency is sufficiently high to support 100Mbps data throughput.

Default Output State and Enable

The ‘F’ variant implements a default-low output state: if the input side loses power or the input signal is absent, the output defaults to logic low. This is critical for fail-safe designs where a high output could trigger unintended operation. Enable pins (EN1, EN2) place the respective outputs in high-impedance state, useful for multi-controller bus driving and power reduction.

Common-Mode Transient Immunity

The ±100kV/µs CMTI is achieved through differential signal transmission across matched capacitor pairs, which cancels common-mode noise. This makes the device highly immune to fast voltage transients common in motor drive and power converter environments.

• Industrial motor drive and inverter systems requiring reinforced isolation with 100kV/µs CMTI for noisy environments
• Isolated RS-485/RS-232/CAN bus communication interfaces where default-low output ensures fail-safe bus states
• Medical equipment isolation complying with IEC 60601-1 end equipment standards via CSA certification
• Electric vehicle onboard chargers and battery management systems requiring 5.7kVrms reinforced isolation
• Isolated gate driver interfaces and power supply feedback loops needing low 11ns propagation delay