Out in Front: August 1, 1996

SGS-Thomson Microelectronics is aiming its ST7537HS1 power-line-modem IC at the home-automation market. The chip, which comes in a 28-pin PLCC, allows the use of ac power lines for half-duplex data transmission at 2400 bps. The modulation scheme is frequency-shift keying (FSK) at 133.05 and 131.85 kHz. These frequencies meet strict European standards on electromagnetic compatibility. SGS-Thomson believes that, in home-automation applications, FSK offers a sensible alternative to AM and various forms of spread-spectrum modulation. AM is inexpensive but has a mixed track record for reliability in power-line communication. Spread spectrum, in contrast, offers higher reliability and higher data rates at higher cost. The new FSK system, on the other hand, delivers much greater reliability and higher data rates than AM at little additional cost, according to the company. The ST7537HS1 costs less than $5 (10,000). The data sheet includes the schematic of an application-circuit that, besides the modem IC, uses 12 capacitors, 10 resistors, six transistors, a crystal, an inductor, a transient limiter, and a transformer.

—by Dan Strassberg

SGS-Thomson Microelectronics, Lincoln, MA. (617) 259-0300.