Insulation is required not only for the signal but also for the power supply.
Installing multiple isolators is inefficient.

Excessively high temperatures are not only harmful to humans. Too high a temperature can also easily cause damage to machinery.

As demand for industrial applications such as factory automation and grid infrastructure equipment increases, the need to add more functions to systems is also growing. Consequently, the burden of achieving optimal performance without raising the temperature of power management systems that supply power to various circuits is increasing.

Data isolators can easily provide signal isolation, but data isolation alone is not sufficient. It is also necessary to isolate the power supply. In some cases, two isolated power supplies are provided to directly power the primary and secondary sides of the isolator, but there are also applications where a secondary power supply is absent. In such cases, a secondary power supply isolated from the primary power supply must be generated.

Figure 1 shows a solution for constructing an isolated power supply using discrete components. A transformer driver operating from the primary power supply generates a push-pull signal to drive the primary winding of the isolation transformer. Depending on the winding ratio, the transformer provides the desired secondary voltage. Following the transformer, a rectifier diode assists in rectification, and then a regulator helps reduce ripple. If the rectifier's output is sufficient for system performance, the regulator can be removed entirely.


Figure 1: Isolated power supply using discrete components

This solution provides excellent power transmission efficiency due to the external transformer, but it increases system cost and board space by using multiple components. If multiple isolators are used in the system, system cost and board space also increase because discrete circuits must be made identically to match the number of isolators.

A single-chip solution providing isolated signals and power can solve these problems. Figure 2 shows TI's ISOW7841, which provides isolated data and power. This device does not require external components to generate isolated power. The integrated DC/DC converter provides up to 650mW of isolated output power, and this integration reduces board space and solution costs.


Figure 2: Isolated power supply and SPI for ISOW7841 ADC sensing application

One might suspect that such integration could raise the temperature of the device and system, potentially causing system failure, but there is no need to worry. Compared to other integrated solutions, the ISOW7841 reinforced isolator with integrated power provides 80% higher efficiency (see Figure 3). High-efficiency power transmission enables driving more output power while maintaining a low temperature and provides the additional power needed to drive other devices. In addition, high efficiency helps to place multiple channels closer together without overheating.

Figure 3: Efficiency comparison of ISOW7841 and competing solutions