How to construct an isolated power supply for an I2C isolator?

There are several options for constructing an isolated power supply for an I2C isolator; the best solution depends on the specific application needs.

One option is to use a transformer driver such as the SN6501, which can be used in a push-pull configuration with a secondary side transformer and an optional rectified low dropout regulator (Figure 1). With a power of up to 1.5 W, the SN6501 can be used as an isolated power supply. This device is highly flexible and can be used in almost all applications. This is because the transformer and turns ratio provide the necessary isolation level and output voltage for the power supply. If you need to provide isolated power to other devices, you can use the SN6505 instead of the SN6501 for up to 5 W of output power. The SN6505 has additional protection features such as overload and short circuit, thermal shutdown, soft start and slew rate control to make it easy for designers to build robust solutions.

Figure 1: Signal and power isolation I2C solution using ISO1541

Another alternative for space-constrained applications is the ISOW78xx family of devices that provide signal and power isolation in a small outline 16-pin package. The ISOW7842 can also be used in conjunction with external components.