ASK/FSK Transmitter Supports Multiple Operating Frequencies September 12, 2008
The MAX7057 crystal-referenced ASK/FSK transmitter can operate at any frequency in the 300 MHz to 450 MHz range with the proper crystal frequency and can transmit data at rates up to 100 kb/s NRZ (50 kbps Manchester coded). It integrates a programmable fractional-N PLL synthesizer with a wideband VCO and capacitors that are user programmable to match the impedance of the power amplifier to the antenna. To improve performance, the device integrates an envelope-shaping resistor between the output of the amplifier and the power supply. This resistor slows the turn-on/-off time of the power amp in ASK mode, reducing the spectral width of the amplifier’s modulated output signal. Additionally, the MAX7057 operates from a single, 2.1V to 3.6V supply, and draws less than 1 ?A in standby mode and less than 8.4 mA in transmit mode (50% duty cycle OOK). Available in a 16-pin SO package, price starts at $1.55 each/1,000. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.
