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2.2

Receive Signal Path

The receive signal is coupled from the line into the kit via the same isolation transformer, T1, as is used by the

transmitter.

2 . 2 . 1

R e c e i ve F i l t e r

Capacitor C10 provides DC isolation. Resistor R10 provides a signal input impedance for the receiver. This resistor,

in combination with D6, provides signal limiting to protect the receiver circuitry from high amplitude transmitter signals

and any large signals coupled in from the line. The receive filter comprised of L5 and C41, in combination with R10,

provides some rejection of out-of-band interference, such as AM broadcast signals. This interference may be coupled

from the line and would otherwise swamp the PLC device's internal receiver circuitry. The response of the receive

filter is shown in

Figure

device.

2.3

Signal Path Component Requirements

The values of the transmit filter passive components are relatively critical; 1% tolerance parts should be used to

ensure an accurate response. The opamps used in the transmit filter implementation must meet the following

requirements:



Gain Bandwidth (GBW) > 50 MHz



Voltage feedback



≥ 12 V

- V



Power Supply Rejection Ration (PSRR) > 70 dB



Total Harmonic Distortion (THD) < -60 dB

The coupling transformer T1 must provide a low DC resistance (<0.5 ), low leakage inductance (<12 H) to

minimize signal loss and isolation, consistent with safety requirements per EN60950 specification. The signal

coupling transformer, T1, used in the CY3272 provides 3750 V isolation, a DC resistance of <0.35  and a leakage

inductance less than 1 H.

Capacitor C9 must be X1 or X2 rated to accommodate the turn-on surge, which occurs when power is applied to the

device, as well as surge immunity according to EN 61000-4-5 and EN 50065-2-1 standards. The capacitor C9, used

in the high voltage board design is a 300 V AC Panasonic ECQUG series metalized polyethylene film device, which is

rated for direct across-line application, accommodating the surge requirements of the previously mentioned

specifications.

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4. Resistors R9 and R11 set the VCC/2 bias voltage required on the receive pin of the PLC

Figure 4. Cypress High Voltage PLC Board Receive Filter Response

Document No. 001-55427 Rev. *E

Cypress Powerline Communication Board Design Analysis