ST ST7540动力线调制解调方案

ST公司的ST7540是 FSK动力线收发器，半双工异步／同步FSK调制解调器. ST7540集成了线路驱动器和5V 和3.3V线性稳压器，单电源7.5 到13.5 V工作．器件通过内部的寄存器来控制工作，可通过同步串行接口进行可编程．其它的功能包括看门狗，时钟输出，输出电流和电压控制，载波／前导检测，发送停止和信道在用与热关断等．ST7540可以采用八个不通的信道(60, 66, 72,76, 82.05, 86, 110, 132.5 kHz)进行通信，有四种不同的波特率(600, 1200, 2400, 4800)和两种精度（1 和0.5）．本文介绍了ST7540的主要性能，方框图
,参考设计的主要特性和评估板电路图以及所用的材料清单（BOM）.

ST ST7540 FSK powerline transceiver
ST7540 transceiver uses Frequency Shift Keying (FSK) modulation to perform a half-duplex communication on a powerline network. It operates from a 7.5 to 13.5 V single supply voltage (Vcc) and integrates a power amplifier (PA), which is able to drive low line impedance, and two linear regulators providing 5 V and 3.3 V.
The ST7540 can communicate using eight different communication channels (60, 66, 72,
76, 82.05, 86, 110, 132.5 kHz), four baud rates (600, 1200, 2400, 4800) and two deviations (1 and 0.5). Additional functions are included, such as watchdog, automatic control on PA output voltage and current, carrier/preamble detection and band-in-use signaling, transmission time-out, and thermal shutdown.

The transceiver, which is dedicated only to physical communication, operates with a
microcontroller whose aim is to manage the communication protocol stack. A reset output
(RSTO) and a programmable clock (MCLK) can be provided to the microcontroller by the
ST7540 in order to simplify the external logic and circuitry.
The host controller can exchange data with the transceiver through a serial interface,
programmable to operate either in UART (CLR/T data clock not used) or in SPI mode.

Communication on the power line can be either synchronous or asynchronous to the data
clock that is provided by the transceiver at the programmed baud rate.
When in transmission mode (i.e. RxTx line at low level), the ST7540 samples the digital
signal on the TxD line at the programmed baud rate and modulates it in a FSK sinusoidal
output on the Tx_OUT line. This signal is then externally fed into the power amplifier to add current capability. The power amplifier can also introduce gain and active filtering to the signal, just using few external passive components. The resulting signal on the PA_OUT line is coupled to the power line.

When in receiving mode (i.e. RxTx line at high level), an incoming FSK signal on the Rx_IN line is demodulated and the digital output is available for the microcontroller on the RxD pin.

The device also recovers the synchronism of the received signal using an internal PLL. The recovered clock is present on CLR/T output.
The ST7540 operating parameters can be set by means of an internal control register,
accessible only through the SPI host interface.
ST7540通用特性：

■Half-duplex frequency shift keying (FSK) transceiver
■Integrated power line driver with programmable voltage and current control
■Programmable mains access:
Synchronous
Asynchronous
■Single supply voltage (from 7.5V up to 13.5V)
■Very low power consumption (Iq = 5mA)
■Integrates 5V voltage regulator (up to 50mA) with short circuit protection
■Integrated 3.3V voltage regulator (up to 50mA) with short circuit protection
■3.3V or 5V digital supply
■8 Programmable transmission frequencies
■Programmable baud rate up to 4800BPS
■Receiving sensitivity up to 250VRMS
■Suitable for applications in accordance with EN 50065 Cenelec specification
■Carrier or preamble detection
■Band in use detection
■Programmable control register
■Watchdog timer
■8 or 16 Bit header recognition
■ST7537 and ST7538 compatible
■UART/SPI host interface



图１．ST7540方框图
The ST7540 reference design has been developed as a useful tool to demonstrate how a
small, high-performance powerline node can be built using the ST7540 FSK transceiver.

With this reference design, it is possible to evaluate the ST7540 features, in particular, its
transmitting and receiving performances through actual communication on the power line.

The ST7540 reference design may be considered to be composed of three main sections:

Power supply section, specifically tailored to match powerline coupling requirements
and to operate within a wide range of the input mains voltage
Modem and crystal oscillator section
Line coupling interface section
The coupling interface is designed to allow the ST7540 FSK transceiver to transmit and
receive on the mains using 72 kHz carrier frequencies, within the European CENELEC
standard A-band specified for automatic meter reading.

The complete evaluation system for the ST7540 powerline communication consists of:
a PC using the ST7540 Power Line Modem Demo Kit software tool
one EVALCOMMBOARD hosting the ST7 microcontroller
one ST7540 reference design board (EVALST7540-1).
The correct procedure for connecting the EVALST7540-1 and the

EVALCOMMBOARD is as　follows:
1.Connect the EVALST7540-1 and the EVALCOMMBOARD
2.Connect the ac mains cable to the EVALST7540-1 and the USB cable to the
EVALCOMMBOARD
3.Connect the EVALST7540-1 to the ac mains supply
4.Connect the EVALCOMMBOARD to the PC via the USB cable.


图２．包括PC, EVALCOMMBOARD和EVALST7540-1板的完整评估系统



图３．EVALST7540-1板的调制解调器和耦合接口电路图



图４．EVALST7540-1板电源电路图



图５．Rx和Tx 滤波器电路图



图６．三相架构原理框图



图７．110 kHz通路的线路耦合接口电路



图７．132.5 kHz通路的线路耦合接口电路
材料清单（BOM）：