Silicon Laboratories was one of the first companies to integrate a full AM/FM broadcast radio on a chip. Its AM/FM and FM-only chips are sold by the millions and are showing up in cell phones, portable radios, and other products. Now, Silicon Labs has added weather radio capability to this product line.
The U.S. Weather Bureau operates a nationwide network of FM weather radio stations operating in the 162.4- to 162.55-MHz spectrum. These stations continuously broadcast local weather conditions, warnings, watches, and hazard information as well as national security and public safety alerts.
With these chips, designers can add weather coverage to a wide range of products (see the figure). Their 1050-Hz warning-tone detection capability enables the radio to automatically turn the receiver on to play incoming warning alerts.
The Si4736 covers the standard AM and FM bands and adds the weather band. The Si4737 has similar coverage and adds RDS/RBDS. The FM-only Si4738 also includes the weather band. The Si4739 adds RDS/RBDS to the FM and weather-band coverage. Available in a 20-pin, 3- by 3-mm quad flat no-lead (QFN) package, prices start at $3.06 in 10,000-unit lots. An evaluation board is available for $150.