11.4 Power-Supply Decoupling

Good power-supply decoupling is important to achieve best performance. AVDD must be decoupled with at least a 330-nF capacitor to AVSS. DVDD and IOVDD (when not connected to DVDD) must be decoupled with at least a 0.1-μF capacitor to DGND. Figure 118 and Figure 119 show typical power-supply decoupling examples for unipolar and bipolar analog supplies, respectively. Place the bypass capacitors as close to the power-supply pins of the device as possible using low-impedance connections. Use multi-layer ceramic chip capacitors (MLCCs) that offer low equivalent series resistance (ESR) and inductance (ESL) characteristics for power-supply decoupling purposes. To reduce inductance on the supply pins, avoid the use of vias for connecting the capacitors to the supply pins. The use of multiple vias in parallel lowers the overall inductance and is beneficial for connections to ground planes. Connect analog and digital grounds together as close to the device as possible.

Figure 118. Unipolar Analog Power Supply

Figure 119. Bipolar Analog Power Supply