The ISOM871x family of devices are opto-emulators that provide isolation for digitals signals of data rates up to 25 Mbps and are single-channel, pin-compatible, drop-in replacements for optocouplers. While standard optocouplers use an LED as the input stage, ISOM871x uses an emulated diode as the input stage. The input stage is isolated from the driver stage by TI's proprietary silicon dioxide-based (SiO₂) isolation barrier, which not only provides robust isolation, but also offers best-in-class common mode transient immunity. Ordering options include CMOS output and open collector output options.

ISOM871x devices isolate high speed digital signals and offer performance, reliability, and flexibility advantages not available with traditional optocouplers. The devices are based on CMOS isolation technology for low-power and high-speed operation, therefore they are resistant to the wear-out effects found in optocouplers that degrade performance with increasing temperature, forward current, and device age.

The functional block diagram of ISOM871x devices is shown in Section 9.2. The input signal is transmitted across the isolation barrier using an on-off keying (OOK) modulation scheme. The transmitter sends a high-frequency carrier across the barrier to represent one digital state and sends no signal to represent the other digital state. The receiver demodulates the signal after advanced signal conditioning and produces the signal through the output stage. These devices also incorporate advanced circuit techniques to maximize CMTI performance and minimize radiated emissions. Figure 9-2 shows conceptual detail of how the OOK scheme works.