Isolated amplifiers are widely used for voltage measurements in high-voltage applications that must be isolated from a low-voltage domain. Typical applications are AC line voltage measurements at the input of a power factor correction (PFC) stage or the output of a solar inverter. Other applications are DC measurements at the output of a PFC stage or DC/DC converter, or phase voltage measurements in motor and servo drives. The AMC3330 integrates an isolated power supply for the high-voltage side and therefore is particularly easy to use in applications that do not have a high-side supply readily available or where a high-side supply is referenced to a different ground potential than the signal to be measured.

Figure 7-1 depicts a simplified schematic of the AMC3330 in a solar inverter where the AC phase voltage on the grid-side must be measured. At that location in the system, there is no supply readily available for powering the isolated amplifier. The integrated isolated power supply, together with its bipolar input voltage range, makes the AMC3330 ideally suited for AC line-voltage sensing. In this example, phase current is sensed by the AMC3301 across a shunt resistor on the grid-side of an LCL filter where there is also no suitable supply available for powering the isolated amplifier. The integrated power supply of the AMC3301 eliminates that problem and enables current sensing at optimal locations for the system.

Figure 7-1 The AMC3330 in a Solar Inverter Application