Digital or galvanic isolation is a technology that prevents current from flowing between two parts of a system, while still allowing the necessary signals and power to be transmitted. This function is important in protecting people and equipment from hazardous voltages and eliminating ground loops to prevent noise in sensitive circuits.

Digital isolation is similar to a contactless payment terminal: there is no physical connection between the card and the terminal, but a magnetic field generated by the terminal transfers power to the card, and the system reads and transmits the payment information.

Digital isolation is commonly used in industrial products such as power converters, industrial automation systems, and electric vehicles. For example, in electric vehicle chargers, digital isolation provides safe isolation between the high-voltage charging circuit and the low-voltage control circuit and operating panel.


■ Three basic technologies: optical, magnetic, and capacitive

There are three basic technologies for digital isolation: optical, magnetic, and capacitive.

In optical isolation, an LED transmits data across an insulating barrier in the form of pulses of light. This light is received by a phototransistor (also called an optocoupler) and converted into an electrical signal.

In magnetic isolation, a magnetic field that acts like a transformer transmits data and supplies power across the isolation barrier. While a regular transformer is used to increase or decrease voltage, an isolation transformer maintains a 1:1 ratio to keep the voltage the same. This type of transformer is mainly used for safety-related applications.

In capacitive isolation, data is transmitted through capacitors in a digital encoding method that charges and discharges the capacitors at high speed. When capacitors are used for isolation in power circuits, they are sometimes given special ratings to indicate the hazards to the system or user in a short circuit situation.

For example, Class-X capacitors are connected between the AC line and AC neutral and reduce the risk of electric shock in the event of a short circuit, but a fire hazard may still exist. Class-Y capacitors, on the other hand, are connected between the AC line and the chassis (metal frame) and, although they pose a lesser fire hazard, may present a shock hazard.

In situations where safety against electric shock hazards is required, it is better to use optical or magnetic isolation technologies instead of capacitive isolation, because when capacitors are connected in series in an AC circuit, current will always flow through the capacitor.

■ Used in situations where the ground potential of each circuit is different

Digital isolation is used in situations where two or more electrical circuits need to communicate with each other, but the ground potentials of each circuit may be different. This technique effectively eliminates ground loops by blocking unwanted currents from flowing through the common ground conductor. Digital isolation is also used for safety purposes, such as preventing electric shock accidents.

# Contributor
Marcel Consee / Mouser Electronics


As a technical content specialist, Marcel is the internal contact for technical inquiries within Mouser's EMEA marketing team. Originally a physicist, he once worked as an editor for an electronics magazine. In real life, he balances his love of electronics with his love of books and beer while raising two children with slightly different chromosomes. So far, he's been able to do both without missing a beat.