By operating in the unlicensed 27-MHz band, the AS3900 frequency-shift-keying (FSK) transceiver avoids the interference found in the popular 2.4-GHz band. As a result, less energy is absorbed by the human body by measure of the specific absorption rate (SAR). The transceiver consumes 2.5 A current in polling mode and typically 3.8 and 4.9 mA in the receive and transmit modes, respectively. The AS3900 transmits data to 212 kb/s. While an RF antenna typically is sized according to the wavelength of the operating frequency, this transceiver operates with a small magnetic-loop antenna that resonates at 27 MHz. Magnetic coupling ensures that the signal travels only a short distance. In addition, the long wavelength at 27-MHz operation allows the AS3900 to provide accurate received-signal-strength-indication (RSSI) signal readings. The transceiver integrates a 32.768-kHz crystal oscillator, 24 b OTP memory on chip, battery-level detection, wakeup receiver functionality, digital RSSI, and a bidirectional serial digital interface (SDI) for simple interfacing. The built-in Link manager offers a hardwired protocol for self-management of all network functions. The AS3900 operates from a 2.2-V power supply (functional down to 2.0 V). P&A: less than $3.00 each in 1000Q.
austriamicrosystems USA, Inc.
Suite 400, 8601 Six Forks Rd.
Raleigh, NC 27615;
(919) 676-5292, FAX: (509) 696-2713