Specifications

PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Book 181
Figure 5.19 10X Power Supply Noise Probe
If the noise masks for either the V
A
or V
DD5
power supplies are not met, then additional filtering must be added to the
offending supply in order to bring it into compliance. In the event that extra filtering is needed an inductor of about
10µH can be added in series with the supply line. When combined with a bulk bypass capacitor of >10µF (on the PL
Smart Transceiver side of the inductor) the LC combination will provide >20dB of attenuation at communication
frequencies. An alternate way to provide a low noise V
DD5
supply is to use a dedicated 5V linear regulator to feed the
PL Smart Transceiver circuitry. In this way noise from other devices on the PCB will be isolated from the V
DD5
supply line of the PL Smart Transceiver. If a switching power supply is used which meets the recommended
operating frequencies of Table 5.8 then additional V
A
and V
DD5
filtering is generally not required.