Isolated ΔΣ modulators are widely used in new-generation frequency inverter designs because of their high ac and dc performance. Frequency inverters are critical parts of industrial motor drives, photovoltaic inverters (string and central inverters), uninterruptible power supplies (UPS), and other industrial applications.
Figure 51 shows a simplified schematic of the AMC1303Mx in a typical frequency inverter application as used in industrial motor drives with shunt resistors (RSHUNT) used for current sensing. Depending on the system design, either all three or only two motor phase currents are sensed.
Figure 52 shows how the Manchester coded bitstream output of the AMC1303Ex minimizes the wiring efforts of the connection between the power and the control board. This bitstream output also allows the clock to be generated locally on the power board without the having to adjust the propagation delay time of each DOUT connection to fulfill the setup and hold time requirements of the microcontroller.
In both examples shown previously, an additional fourth AMC1303 is used to support isolated voltage sensing of the dc link. This high voltage is reduced using a resistive divider and is sensed by the device across a smaller resistor. The value of this resistor can degrade the performance of the measurement, as described in the Isolated Voltage Sensingsection.