Nippon Precision Circuits (NPC)^*1 has started delivering the sample of the CF9501A (chip), the industry's first receiver IC for radio wave watches^*2 that has a built-in 2-station tuning selector circuit. This IC can realize a high input sensitivity and a wide input dynamic range (input voltage range) with a few components.

Watch-related manufacturers consider radio wave watches as the main thrust for the future and make efforts to develop new products and appeal to the users. Many stores have a space dedicated to sales of radio wave watches, and this has energized the watch market that was once stagnant, and increased sales. A radio wave watch is simpler in structure and consumes less power than a system that uses GPS to obtain time information, and can be used in a low-cost system that requires accurate time information.

Against this background of the watch market, NPC has developed the CF9501A receiver IC for radio wave watches by making the best use of its analog technology. The CF9501A is an IC that amplifies and detects the standard radio wave in the long-wave band received through antenna, and outputs binary time codes. The main features of the CF9501A are:

Features of CF9501A
1.	Industry's first 2-station tuning selector circuit built in If two transmission stations using different carrier frequencies exist like in Japan, the tuning frequency must be changed for the region of reception. One method of changing the tuning frequency is to change the capacitance of the tuning capacitor. To do this, external components such as an analog switch, as well as a receiver IC, were necessary in the past. Equipped with a built-in CMOS analog switch with low ON resistance, the CF9501A can solve the restrictions of design because of the number of components necessary and the problem of cost.
2.	High input sensitivity and wide input dynamic range realized by BiCMOS Thanks to employment of NPC's original BiCMOS process, the analog switch block, which requires a low ON resistance, and the logic block of the CF9501A are made up of CMOS transistors. The blocks that process weak signals susceptible to noise consist of bipolar transistors. As a result, a high input sensitivity and a wide input dynamic range have been realized, while an analog switch block and a logic block are integrated on a single chip. In addition to the chip CF9501A, NPC also plans to release a 16-pin VSOP package model, the SM9501AV. Moreover, it also plans to expand its lineup of receiver ICs for radio wave watches that can operate at a lower voltage and consume less power.

A radio wave watch that accurately makes time can automatically correct an error by using the time information of standard radio wave in the long-wave band. In Japan, time information transmission service that superimposes and transmits information on Japan's standard time on a long wave of 40 kHz. This service was started by Fukushima Standard Radio Wave Station (JJY) of the Communication Research Laboratory (CRL) in 1999. In 2001, Kyushu Standard Radio Wave Station started transmission at a carrier frequency of 60 kHz. Consequently, the standard radio wave in the long-wave band can be received favorably throughout Japan. This has improved recognition of radio wave watches, and the watches have become widespread. Transmission of time information by the standard radio wave in the long-wave band has also been increasingly popular throughout the world.

^*1: Main office: 2-4-3 Fukusumi, Koto-ku Tokyo, President: Yoshifumi Gomi
^*2: Radio wave watch