+

+

N1

N2

Phase

Neutral

Low-Voltage

Capacitor

High-Voltage

Capacitor

Power

Amplifier

MOV

TVS

PA

Power Supply

D2

D1

D3

Device

Copyright © 2017, Texas Instruments Incorporated

+

+

N1

N2

Phase

Neutral

Low-Voltage

Capacitor

High-Voltage

Capacitor

L

Power

Amplifier

Copyright © 2017, Texas Instruments Incorporated

11

OPA521

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SBOS872 – MAY 2018

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Copyright © 2018, Texas Instruments Incorporated

Figure 3. Simplified Line-Coupling Circuit

8.2.2.3 Circuit Protection

Power-line communications are often located in operating environments that are harsh for electrical components

connected to the AC line. Noise or surges from electrical anomalies (such as lightning, capacitor bank switching,

inductive switching, or other grid fault conditions) can damage high-performance integrated circuits if proper

protection is not provided. The power amplifier can survive the harshest conditions by using a variety of

techniques to protect the device.

Lay out the protection circuitry to dissipate as much of the electrical disturbance as possible with a multilayer

approach using metal-oxide varistors (MOVs), transient voltage suppression diodes (TVSs), Schottky diodes, and

a Zener diode. These components dissipate the electrical disturbance before the anomaly reaches the device.

Figure 4 shows the recommended strategy for transient overvoltage protection.

Figure 4. Transient Overvoltage Protection

The high-voltage coupling capacitor must be able to withstand pulses up to the clamping protection that are

provided by the MOV. A metalized polypropylene capacitor (such as the 474MKP275KA from Illinois Capacitor™)

is rated for 50 Hz to 60 Hz and 250 VAC to 310 VAC, and withstands 24 impulses of 2.5 kV.