Isolated modulators 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 of an onboard charger (OBC), DC measurements at the output of a PFC stage or DC/DC converter, or phase voltage measurements in traction inverters. The AMC3336-Q1 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 8-1 shows a simplified schematic of the AMC3336-Q1 in an OBC where the AC phase voltage on the grid-side must to be measured. At that location in the system, there is no supply readily available for powering the isolated modulator. The integrated isolated power supply, together with its bipolar input voltage range, makes the AMC3336-Q1 ideally suited for AC line-voltage sensing.

At the output of the PFC stage a second AMC3336-Q1 is used for sensing the DC-link voltage. This example also shows the proper connection for implementing a differential measurement that typically results in best measurement accuracy and linearity.