TH71221 datasheet(5/44 Pages) MELEXIS

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TH71221

27 to 930MHz

FSK/FM/ASK Transceiver

39010 071221

Page 5 of 44

Data Sheet

Rev. 009

Nov/15

1.4

Block Diagram

Fig. 1:

TH71221 block diagram

1.5

User Mode Features

The transceiver can operate in two different user modes. It can be used either as a 3wire-bus-controlled

programmable or as a stand-alone fixed-frequency device. After power up, the transceiver is set to Stand-

alone User Mode (SUM). In this mode, pins FS0/SDEN and FS1/LD must be connected to VEE or VCC in

order to set the desired frequency of operation. There are 4 pre-defined frequency settings: 315MHz,

433.92MHz, 868.3MHz and 915MHz. The logic level at pin FS0/SDEN must not be changed after power up

in order to remain in fixed-frequency mode.

After the first logic level change at pin FS0/SDEN, the transceiver enters into Programmable User Mode

(PUM). In this mode, the user can set any PLL frequency or mode of operation by the SCI. In SUM pins

FS0/SDEN and FS1/LD are used to set the desired frequency, while in PUM pin FS0/SDEN is part of the

3-wire serial control interface (SCI) and pin FS1/LD is the look detector output signal of the PLL synthesizer.

A mode control logic allows several operating modes. In addition to standby, transmit and receive mode, two

idle modes can be selected to run either the reference oscillator only or the whole PLL synthesizer. The PLL

settings for the PLL idle mode are taken over from the last operating mode which can be either receive or

transmit mode.

The different operating modes can be set in SUM and PUM as well. In SUM the user can program the trans-

ceiver via control pins RE/SCLK and TE/SDTA. In PUM the register bits OPMODE are used to select the

modes of operation while pins RE/SCLK and TE/SDTA are part of the SCI.

IN_LNA

LNA

MIX

IFA

1.5pF

IN_DEM

MIX

Demodulator

FSK

OUT_DTA

OA2

bias

OUT_DEM

SW1

SW2

OA1

INT1

INT2/PDO

200k

VEE_PLL

OUT_PA

FSK

ASK

PS_PA

counter

Control Logic

SCI

PKDET

VCO

VCC_PLL

TNK_LO

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