ST7538Q datasheet(26/44 Pages) STMICROELECTRONICS

26 / 44 page

Functional description

ST7538Q

26/44

5.8

Transmission mode

The transmit mode is set when RxTx Pin = ”0” and REG_DATA Pin = ”0”. In transmitting

mode the FSK Modulator and the Power Line Interface are turned ON. The transmit Data

(TXD) enter synchronously or asynchronously to the FSK modulator.

●

Host Controller Synchronous Communication Mode: on CLR/T rising edge, TXD Line

Value is read and sent to the FSK Modulator. ST7538Q Manages the Transmission

timing according to the BaudRate Selected

●

Host Controller Asynchronous Communication Mode: TXD data enter directly to the

FSK Modulator.The Host Controller Manages the Transmission timing

In both conditions no Protocol Bits are added by ST7538Q.

The FSK frequencies are synthesized in the FSK modulator from a 16MHz crystal oscillator

by direct digital synthesis technique. The frequencies Table in different Configuration is

reported in Table 7. The frequencies precision is same as external crystal one’s.

In the analog domain, the signal is filtered in order to reduce the output signal spectrum and

to reduce the harmonic distortion. The transition between a symbol and the following is done

at the end of the on-going half FSK sinewave cycle.

Figure 13. Transmitting path block diagram

TRANSMISSION

FILTER

FSK

MODULATOR

D-TYPE

FLIP

FLOP

DAC

TIMER

THERMAL

SENSOR

VOLTAGE

LOOP

CURRENT

LOOP

CLR/T GENERATOR

ZERO CROSSING

Vsense

ATOP2

ATOP1

ATO

CLR/T

TxD

TOUT

ZCIN

ZCOUT

Bit 14

Bit 0-5

Bit 0-2

Bit 7 & 8

Band Pass

PLI

ALC

PLI

D03IN1420

Bits 17 & 21

ST7538Q 数据表(PDF) 26 Page - STMicroelectronics

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