9 Power Supply Recommendations

The AMC3306M05 is powered from the low-side power supply (VDD) with a nominal value of 3.3 V or 5 V. TI recommends a low-ESR decoupling capacitor of 1 nF (C8 in Figure 9-1) placed as close as possible to the VDD pin, followed by a 1-μF capacitor (C9) to filter this power-supply path.

The low-side of the DC/DC converter is decoupled with a low-ESR, 100-nF capacitor (C4) positioned close to the device between the DCDC_IN and DCDC_GND pins. Use a 1-μF capacitor (C2) to decouple the high-side in addition to a low-ESR, 1-nF capacitor (C3) placed as close as possible to the device and connected to the DCDC_OUT and DCDC_HGND pins.

For the high-side LDO, use low-ESR capacitors of 1-nF (C6), placed as close as possible to the AMC3306M05, followed by a 100-nF decoupling capacitor (C5).

The ground reference for the high-side (HGND) is derived from the terminal of the shunt resistor that is connected to the negative input (INN) of the device. For best DC accuracy, use a separate trace to make this connection instead of shorting HGND to INN directly at the device input. The high-side DC/DC ground terminal (DCDC_HGND) is shorted to HGND directly at the device pins.

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

Table 9-1 lists components suitable for use with the AMC3306M05. This list is not exhaustive. Other components may exist that are equally suitable (or better), however these listed components have been validated during the development of the AMC3306M05.