10 Power Supply Recommendations

In a typical application, the high-side (VDD1) of the AMC1311 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 and a transformer that supports the desired isolation voltage ratings.

The AMC1311 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 10-1 shows the proper decoupling layout for the AMC1311.

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.