AN4444 datasheet(35/68 Pages) STMICROELECTRONICS

Part #	AN4444

Description	ST7590 PRIME compliant power line networking SoC design guide

PDF	68 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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35 / 68 page

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AN4444

ST7590 reference design description

Figure 25. Montecarlo simulation of the reception external amplifier with automatic attenuation

8.1.4

Zero crossing coupling

The zero crossing coupling circuit is aimed at providing a bipolar (AC) signal synchronous

with the mains network voltage to the ZC_IN pin. This signal must be centered on VSS and

limited to ± 5 V peak (see Part 1 of Section 13: References on page 63).

The isolated zero crossing circuit is realized through an optocoupler in non-inverting

configuration. Neutral and phase lines are brought to the optocoupler through 33 k



resistors in series, as represented in Figure 26. The STTH1L06A diode protects photodiode

during negative half-wave. The three 33 k

 series resistors limit the photodiode input

current to nearly 2 mA rms at 230 V AC. Having two resistors on the L line helps preventing

short-circuits in case of resistor degradation.

Figure 26. Isolated zero crossing coupling circuit

AN4444 Datasheet(PDF) 35 Page - STMicroelectronics