The ISOM811x opto-emulators are pin-compatible, single-channel, drop-in replacements for many traditional optocouplers. While standard optocouplers use an LED as the input stage, ISOM811x uses an emulated LED as the input stage. The input and output stages are isolated by TI's proprietary silicon dioxide-based (SiO₂) isolation barrier. This isolation technology makes ISOM811x resistant to the wear-out effects found in optocouplers that degrade performance with increasing temperature, forward current, and device age. Ordering options include four different ranges of current transfer ratio (CTR) and input options supporting uni-polar and bi-polar DC flow.

The ISOM811x family of devices isolate DC and bi-directional DC signals and offer performance, reliability, and flexibility advantages not available with traditional optocouplers.

The functional block diagram of ISOM811x devices are 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 that contains information on how much current is flowing through the input pins. 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 bandwidth and minimize radiated emissions. Figure 9-3 shows conceptual details of how the OOK scheme works.