In a typical frequency inverter application, the high-side power supply for the AMC1200 (VDD1) is derived from the system supply, as shown in Figure 36. For lowest cost, a Zener diode can be used to limit the voltage to 5 V ± 10%. TI recommends using a 0.1-µF, low-ESR decoupling capacitor for filtering this power-supply. TI also recommends using a 0.1-µF decoupling capacitor for filtering the power-supply on the VDD2 side. For best performance, place these capacitors (C₁ and C₄) as close as possible to the VDD1 and VDD2 pins respectively. If better filtering is required, an additional 1-µF to 10-µF capacitor can be used in parallel to C₁ and C₄.

Figure 36. Zener Diode Based High-Side Supply

For higher power efficiency and better performance, a buck converter can be used; an example of such an approach is based on the LM5017. A reference design including performance test results and layout documentation can be downloaded at PMP9480, Isolated Bias Supplies + Isolated Amplifier Combo for Line Voltage or Current Measurement.