1 Isolator Construction

Even though both digital isolators and optocouplers offer similar functionality, these devices are quite different in construction and working principle. Optocouplers use an LED to transmit digital or analog information across an isolation (or insulation) barrier (often just an air gap). Some optocouplers use epoxy as the insulating material which offers slightly better dielectric strength than air, as shown in Figure 1-1. Conversely, digital isolators can utilize either capacitive or magnetic isolation. Capacitive digital isolators are constructed with two series isolation capacitors using SiO₂ as the dielectric, as shown in Figure 1-2. Magnetic isolation utilizes coils separated by a dielectric. TI utilizes SiO2 for both capacitive and magnetic isolation, offering one of the highest dielectric strengths among insulating materials and significantly stronger performance compared to dielectrics used by competing isolation technologies, as shown in Table 1-1.