9.3 Power Supplies

The AFE031 has two low-voltage analog power-supply pins and one low-voltage digital supply pin. Internally, the two analog supply pins are connected to each other through back-to-back electrostatic discharge (ESD) protection diodes. These pins must be connected to each other on the application printed circuit board (PCB). It is also recommended to connect the digital supply pin and the two analog supply pins together on the PCB. Both low-voltage analog ground pins are also connected internally through back-to-back ESD protection diodes. These ground pins should also be connected to the digital ground pin on the PCB. It is recommended to bypass the low-voltage power supplies with a parallel combination of a 10-μf and 100-nf capacitor. The PA block is biased separately from a high-voltage, high-current supply.

Two PA power supply pins and two PA ground pins are available to provide a path for the high currents associated with driving the low impedance of the ac mains. Connecting the two PA supply pins together is recommended. It is also recommended to place a bypass capacitor of 47 μF to 100 μF in parellel with 100 nF as close as possible to the AFE031. Care must be taken when routing the high current ground lines on the PCB to avoid creating voltage drops in the PCB ground that may vary with changes in load current.

The AFE031 has many options to enable or disable the functional blocks to allow for flexible power-savings modes. Table 7 shows the specific power supply that each functional block draws power from, as well as the typical amount of power drawn from the associated power supplies for both the enabled and disabled states. For additional information on power-supply requirements refer to Application Report SBOA130, Analog Front-End Design for a Narrowband Power-Line Communications Modem Using the AFE031 (available for download at www.ti.com).