With the increasing popularity of digital isolators in industrial and automotive applications, designers will face many available options. Most digital isolators are designed according to specific system requirements and applications, so the selected device needs to be considered Whether it meets the requirements of your system. So, how do we choose the right digital isolator?

1. Know your isolation specifications

Before choosing a digital isolator, some parameters related to isolation design in the data sheet should be considered.

Isolation withstand voltage: Is basic isolation and ≤3,000 VRMS sufficient to meet your design requirements? Or the design requirement requires ≥5,000 VRMS? This specification is usually set by the legal requirements of the system, which means that the isolator can persist for at least 60 seconds without voltage breakdown. Generally, general regulatory requirements specify this specification, which means that the isolator can withstand a voltage of at least 60 seconds in the case of breakdown.

Operating voltage: Some factors (such as package size, pollution degree, and material group) may affect the operating voltage of a component.

Surge isolation rating: If your design requires enhanced isolation, you can consider this parameter and ensure that this isolator can withstand surge pulses of <10-kV.

Creepage distance/clearance: Is the creepage distance/clearance of the 4mm package sufficient, or does your system standard require 8mm or higher specifications?

Common Mode Transient Immunity (CMTI): If your design is used in a high-noise environment, a higher CMTI rating will be very important for your digital isolator.

Power consumption: Is the overall system power consumption a key specification in your design? If so, you can pay attention to the current consumption specifications of each channel of each isolator device.

Data rate: What data rate does your communication interface require? Are you running a low-speed UART speed or a high-speed ≥100-Mbps data protocol?

2. Choose the right package

Packages vary greatly in isolation, because the size and characteristics of the package directly affect the high-voltage capability of the device. Larger packages, longer creepage distances and electrical clearances allow higher isolation voltage specifications. The small packaging can save the space and cost of the circuit board. In addition, you also need to consider how many isolation channels are needed for the communication interface, because the number of channels also affects the type of package.

3. Determine the number and configuration of the required channels

Before choosing an isolator, you should determine how many channels are needed to isolate the signals and the direction of each signal. These factors will determine the number and configuration of channels required. In addition, when the input channel of the digital isolator is not powered on or the pin is floating, considering the preferred default output state (or fail-safe state) will help determine the predefined state (high level or low level) of the output pin . The default high-level or default low-level output has corresponding options.