MAX7057 300MHz to 450MHz ASK/FSK Transmitter Supports Multiple Operating Frequencies with One Crystal

• The MAX7057 is a crystal-referenced, phased-locked loop VHF/UHF transmitter for transmitting ASK/FSK data over a wide range of frequencies.
• This device supports any frequency in the 300MHz to 450MHz range with the use of a single crystal reference, and it ensures that the output of the power amplifier stays matched to the antenna or load.
• To enable these benefits, the MAX7057 integrates a programmable fractional-N PLL, as well as internal tuning capacitors at the output of the power amplifier that can be programmed to match the antenna or load.
• The MAX7057 is ideal for power-sensitive applications such as home security systems, remote controls, and garage door openers.

SUNNYVALE, CA—September 8, 2008—Maxim Integrated Products (PINK OTC MARKETS: MXIM) introduces the MAX7057 crystal-referenced, phased-locked loop (PLL) VHF/UHF transmitter for transmitting OOK/ASK/FSK data over a wide range of frequencies. This device can operate at any frequency in the 300MHz to 450MHz range with the proper crystal frequency, and it can transmit data at up to 100kbps NRZ (50kbps Manchester coded).

To enable this flexibility, the MAX7057 integrates a programmable fractional-N PLL synthesizer with a wideband VCO. Additionally, it features internal capacitors that can be programmed to match the impedance of the power amplifier (PA) to the antenna. This topology ensures highly efficient transmission at multiple operating frequencies, thus making the MAX7057 ideal for power-sensitive applications such as home security systems, remote controls, and garage door openers.

To further improve performance, the MAX7057 integrates an envelope-shaping resistor between the output of the PA and the power supply. This resistor slows the turn-on/off time of the PA in ASK mode, reducing the spectral width of the PA's modulated output signal.

The MAX7057's crystal-based architecture eliminates many of the common problems with SAW transmitters by providing greater modulation depth, faster frequency settling, tighter transmit-frequency tolerance, and reduced temperature dependence. This device thus provides better overall receiver performance when using a superheterodyne receiver with a narrow-IF (i.e., lower noise) bandwidth.

The MAX7057 operates from a single, 2.1V to 3.6V supply, and draws less than 1μA in standby mode and less than 8.4mA in transmit mode (50% duty cycle OOK). Available in a 16-pin SO package, this device is fully specified over the -40°C to +125°C automotive temperature range. Prices start at $1.55 (1000-up, FOB USA).