Low-Cost, 315MHz and 433.92MHz ASK Transceiver with Fractional-N PLL

The MAX7030 crystal-based, fractional-N transceiver is designed to transmit and receive ASK/OOK data at factory-preset carrier frequencies of 315MHz or 433.92MHz with data rates up to 33kbps (Manchester encoded) or 66kbps (NRZ encoded). This device generates a typical output power of +10dBm into a 50Ω load and exhibits typical sensitivity of -114dBm. The MAX7030 features separate transmit and receive pins (PAOUT and LNAIN) and provides an internal RF switch that can be used to connect the transmit and receive pins to a common antenna.

The MAX7030 transmit frequency is generated by a 16-bit, fractional-N, phase-locked loop (PLL), while the receiver's local oscillator (LO) is generated by an integer-N PLL. This hybrid architecture eliminates the need for separate transmit and receive crystal reference oscillators because the fractional-N PLL is preset to be 10.7MHz above the receive LO. Retaining the fixed-N PLL for the receiver avoids the higher current-drain requirements of a fractional-N PLL and keeps the receiver current drain as low as possible. All frequency generation components are integrated on-chip, and only a crystal, a 10.7MHz IF filter, and a few discrete components are required to implement a complete antenna/digital data solution.

The MAX7030 is available in a small, 5mm × 5mm, 32-pin thin QFN package, and is specified to operate over the automotive -40°C to +125°C temperature range.

Applications

* 2-Way Remote Keyless Entry * Garage Door Openers * Home Automation * Local Telemetry Systems * Remote Controls * Remote Sensing * Security Systems * Smoke Alarms

* +2.1V to +3.6V or +4.5V to +5.5V Single-Supply Operation

* Single-Crystal Transceiver

* Factory-Preset Frequency (No Serial Interface Required)

* ASK/OOK Modulation

* +10dBm Output Power into 50Ω Load

* Integrated TX/RX Switch

* Integrated Transmit and Receive PLL, VCO, and Loop Filter

* > 45dB Image Rejection

* Typical RF Sensitivity*: -114dBm

* Selectable IF Bandwidth with External Filter

* < 12.5mA Transmit-Mode Current

* < 6.7mA Receive-Mode Current

* < 800nA Shutdown Current

* Fast-On Startup Feature, < 250µs

* Small, 32-Pin, Thin QFN Package