In a typical frequency inverter application, the high-side power supply (AVDD) for the AMC1204 and AMC1204B is derived from the power supply of the upper gate driver. For lowest cost, a Zener diode can be used to limit the voltage to 5 V ±10%. TI recommends a decoupling capacitor of 0.1 µF for filtering this power-supply path. This capacitor (C₁ in Figure 55) should be placed as close as possible to the AVDD pin for best performance. If better filtering is required, an additional 1-µF to 10-µF capacitor can be used. The floating ground reference AGND is derived from the end of the shunt resistor, which is connected to the negative input (VINN) of the AMC1204 and AMC1204B. If a four-terminal shunt is used, the inputs of AMC1204 and AMC1204B are connected to the inner leads, while AGND is connected to one of the outer leads of the shunt. Both digital signals, CLKIN and DATA, can be directly connected to a digital filter.

1. Place C₁ close to the AMC1204 and AMC1204B.

Figure 55. Zener-Diode-Based High-Side Power Supply

For better performance, the differential input signal is filtered using RC filters (components R₂, R₃, and C₂). Optionally, C₃ and C₄ can be used to reduce charge dumping from the inputs. In this case, care should be taken when choosing the quality of these capacitors: any mismatch in the capacitor values can cause a common-mode error at the input of the modulator.