ADUM2401CRIZ-RL

Measurement devices used in industrial environments often require isolation for user and system safety, and to ensure accurate measurements in the presence of high common-mode voltages. Digital isolators offer a reliable and easy to use alternative to older technologies such as optocouplers. Utilizing digital isolators, engineers can optimize isolated system designs for reduced power consumption and guaranteed system performance without resorting to excessive design margin to make up for missing or incomplete device specifications.
Isolation amplifiers were an initial solution to this problem, but have been outdated with the need for measurements with higher bandwidth and resolution. Today, the most accurate, economical, and efficient technique for performing these measurements is to isolate the entire measurement front end, including the analog-to-digital converter (ADC), and to implement an isolated serial link to the rest of the system.

Up until about ten years ago, optocouplers were one of the few practical solutions for isolating digital signals. However, ask any engineer who has had to design with them, and you will quickly learn how challenging it is to develop an efficient and reliable system, especially when trying to keep costs to a minimum. Optocouplers use an LED to generate light across an isolation barrier to turn a phototransistor on and off. When designing with optocouplers, you have to guarantee that the LED will generate enough light to turn on the receiving phototransistor, and that the output rise and fall times will be fast enough to support operation at the desired frequency. One of the most important optocoupler specifications is the current transfer ratio. The CTR is the ratio of the collector current that appears at the phototransistor to the current through the LED

Measurement devices used in industrial environments often require isolation for user and system safety, and to ensure accurate measurements in the presence of high common-mode voltages. Digital isolators offer a reliable and easy to use alternative to older technologies such as optocouplers. Utilizing digital isolators, engineers can optimize isolated system designs for reduced power consumption and guaranteed system performance without resorting to excessive design margin to make up for missing or incomplete device specifications.
Isolation amplifiers were an initial solution to this problem, but have been outdated with the need for measurements with higher bandwidth and resolution. Today, the most accurate, economical, and efficient technique for performing these measurements is to isolate the entire measurement front end, including the analog-to-digital converter, and to implement an isolated serial link to the rest of the system.

When isolated measurement systems use high sample rates, isolating a serial bus with optocouplers can become a daunting task. The parasitic capacitance of the receiver photodiode limits the speed at which an optocoupler can pass digital signals. You can charge this parasitic capacitance faster by increasing the amount of light coming from the LED, but this increases power consumption. In addition, few optocouplers offer more than two channels per package, only in the same direction, and do not typically include timing specifications related to channel-to-channel matching. While it is logical to assume good matching between optocouplers in the same package, not having a printed specification means you must make an engineering assumption. As is the case when relying on unprinted specifications, most prudent engineers will opt to leave ample design margin, operating at a much lower performance than a data sheet would indicate when considering a single optocoupler.