Maxim Integrated Products has introduced MAX7030/MAX7031*/MAX7032 family of crystal-referenced VHF/UHF transceivers, which delivers more than +10 dBm output power and -114 dBm(MAX7030/MAX7032 in ASK mode)/-110dBm (MAX7031/MAX7030 in FSK mode) sensitivity. Housed in a small, 5 mm x 5 mm, 32-pin TQFN package, these transceivers are aimed at low-cost, high-volume applications where space is critical. Typical applications include two-way key fobs, security products, garage door openers, and remote sensors operating in the 300 MHz to 450 MHz band.

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The MAX7030 transmits and receives OOK/ASK data at a factory-set frequency in the 300 MHz to 450 MHz band with a data rate up to 66 kbps NRZ, typical output power of +10 dBm into a 50 Ohm load, and typical receive sensitivity of -114 dBm. This device has separate transmit (PAOUT) and receive (LNAIN) pins. An internal RF switch can be used to connect these transmit and receive pins to a common antenna.

The MAX7030 integrates a fractional-N PLL in its transmitter and a fixed-N PLL in its receiver. This hybrid architecture eliminates the need for a separate transmit-and-receive crystal reference oscillator because the fractional-N PLL allows the transmit frequency to be set close to the receive frequency with high precision. The MAX7030's on-chip, 16-bit, fractional-N PLL allows frequency multiplication of the low-frequency crystal to frequency steps of f(crystal)/4096. Retaining the fixed-N PLL for the receiver avoids the higher current-drain requirements of a fractional-N PLL, hence keeping the receiver current drain as low as possible. With all VCO and PLL parts on chip, the only key discrete components needed are a crystal and a 10.7 MHz IF filter. The baseband data-filter bandwidth can be set with two external capacitors. ASK data of up to 66 kbps NRZ can be transmitted/received after 250 microseconds from the enable command.

Similar to the MAX7030, the new MAX7031 transmits/receives FSK data at a factory-set frequency in the 300 MHz to 450 MHz band with a factory-set frequency deviation. The MAX7031 has the same data rate and typical output power as the MAX7030, but its typical receive sensitivity is -110 dBm. The MAX7032 not only transmits/receives FSK data, but also OOK/ASK data in the 300 MHz to 450 MHz band with the same typical output power of +10 dBm into a 50 Ohm load. It has a typical receive sensitivity of -114 dBm (ASK)/-110 dBm (FSK). Due to the fractional-N architecture of the MAX7032 transmit PLL, the transmit FSK signal can be programmed for exact frequency deviations. Therefore, the problems associated with oscillator-pulling FSK signal generation are completely eliminated. The MAX7032 is programmed through a three-wire SPI bus. ASK or FSK data of up to 66kbps NRZ can be transmitted/received after 250 microseconds from the enable command. The MAX7030/MAX7031/MAX7032 draw less than 7 mA in receive mode and less than 13 mA in CW transmit mode. All three devices operate over the automotive temperature range (-40°C to +125°C). Prices start at $2.30 (10,000-up, FOB USA). Evaluation kits are available to speed designs.