9 Power Supply Recommendations

The AMC1302 does not require any specific power up sequencing. The high-side power-supply (VDD1) is decoupled with a low-ESR 100-nF capacitor (C1) parallel to a low-ESR 1-µF capacitor (C2). The low-side power supply (VDD2) is equally decoupled with a low-ESR 100-nF capacitor (C3) parallel to a low-ESR 1-µF capacitor (C4). Place all four capacitors (C1, C2, C3, and C4) as close to the device as possible.

The ground reference for the high-side (GND1) is derived from the end of the shunt resistor, which is connected to the negative input (INN) of the device. For best DC accuracy, use a separate trace (as shown in Figure 9-1) to make this connection instead of shorting GND1 to INN directly at the device input. If a four-terminal shunt is used, the device inputs are connected to the inner leads and GND1 is connected to the outer lead on the INN-side of the shunt.

Capacitors must provide adequate effective capacitance under the applicable DC bias conditions they experience in the application. Multilayer ceramic capacitors (MLCCs) typically exhibit only a fraction of their nominal capacitance under real-world conditions and this factor must be taken into consideration when selecting these capacitors. This problem is especially acute in low-profile capacitors, in which the dielectric field strength is higher than in taller components. Reputable capacitor manufacturers provide capacitance versus DC bias curves that greatly simplify component selection.