9 Power Supply Recommendations

In a typical application, the high-side (VDD1) of the AMC1311-Q1 is powered from an already existing, high-side, ground-referenced, 3.3-V or 5-V power supply in the system. Alternatively, the high-side supply can be generated from the low-side supply (VDD2) by an isolated DC/DC converter. A low-cost solution is based on the push-pull driver SN6501-Q1 and a transformer that supports the desired isolation voltage ratings.

The AMC1311-Q1 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. Figure 9-1 shows the proper decoupling layout for the AMC1311-Q1.

Capacitors must provide adequate effective capacitance under the applicable DC bias conditions they experience in the application. Multilayer ceramic capacitors (MLCC) 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.