XE1205I074TRLF データシートの表示（PDF） - Semtech Corporation

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XE1205I074TRLF

180 MHz – 1GHz Low-Power, High Link Budget Integrated UHF Transceiver

Semtech Corporation 

XE1205

5 DESCRIPTION

The XE1205 is a direct conversion (Zero-IF) half-duplex data transceiver. It includes receiver, transmitter, frequency

synthesizer and control logic. The circuit is intended primarily for operation in the following three ISM frequency bands

433 MHz, 868 MHz, and 915 MHz with a same 39MHz reference crystal and uses 2-level FSK modulation.

Operation of the XE1205 over the frequency range 180 MHz - 1000 MHz beyond the ISM bands described above can be

achieved by modifying the reference oscillator crystal frequency. Please contact Semtech for more details.

The XE1205 is programmed by a microcontroller through the 3-wire fully-compatible SPI serial bus (MOSI, MISO, and

SCK) to write to and read from the configuration registers.

The circuit consists of the following main functional blocks:

The receiver converts the incoming 2-level FSK modulated signal into a synchronized bit stream. The receiver comprises

a low-noise amplifier, down-conversion mixers, baseband filters, baseband amplifiers, limiters, demodulator and bit

synchronizer. The bit synchronizer transforms the data output of the demodulator into a glitch-free bit stream DATAOUT

and synchronized clock DCLK. This may be easily used to sample the DATAOUT signal with minimal external processor

overhead. In addition, the receiver includes a Received Signal Strength Indicator (RSSI) function and a Frequency Error

Indicator (FEI) function that provides an indication of the local oscillator frequency error. A pattern recognition function

may be used to detect a user-programmable reference word in the incoming bit stream. The bandwidth of the base-band

filters, the frequency deviation of the expected incoming FSK signal as well as the bit rate of the received data signal are

all user-programmable. The receiver also embeds an automatic frequency offset cancellation to compensate local

oscillator drifts due to XTAL.

The transmitter performs the modulation of the carrier by an input baseband data signal and the transmission of the

modulated signal. The frequency synthesizer is modulated directly. The modulated signal is then amplified by the on-chip

RF power amplifier. The output power is user-programmable to one of four possible values. The frequency deviation and

the bit rate for the transmit signal are the same as those programmed for the receiver section. User-defined pre-filtering

should be enabled to ensure compliance with the requirements of ETSI EN 300 220-1 regarding transmission at 25 kHz

channel spacing.

The frequency synthesizer generates the local oscillator (LO) signal for the receiver section as well as the FSK

modulated signal for the transmitter section. The core of the synthesizer is implemented with a PLL structure. The

frequency is user-programmable with a frequency resolution of approximately 500 Hz in the 433 MHz, 868 MHz and 915

MHz ISM frequency bands. This section includes a crystal oscillator whose signal is the reference for the PLL. This

reference frequency is divided by 2, 4, 8, 16, or 32 and is made available at the CLKOUT pin to serve as a clock signal

for an external processor.

The control block generates the control signals according to the setting in its set of configuration registers.

The service block performs all the necessary functions for the circuit to work properly, including the internal voltage and

current sources.

5.1 DATA OPERATION MODES

The XE1205 is user-programmable between two modes of operation:

Continuous mode: each bit transmitted or received is accessed directly at the DATA input/output pin.

Buffered mode: a 16-byte FIFO is used to store each data byte transmitted or received. This data is written to/read from

the FIFO via the SPI bus. It reduces processor overhead.

© Semtech 2008

www.semtech.com

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