Single-Chip Baseband ICs

The SC14404 (handset) and SC14425 (basestation) are single chip baseband ICs designed to operate in the two popular ISM band frequencies. They are the first of a new family of highly integrated, next generation, single-chip Digital Cordless Telephony baseband processors optimized for the US market.

The handset chip offers a programmable RF interface to fulfill the FCC requirements for 900MHz and 2.4GHz cordless voice and data applications, as well as the requirements for the 1.9GHz DECT standard. The handset baseband chip includes Flash PROM (320kbyte) and EE function (4kbyte). Other integrated features include two on-chip voltage regulators, DC-DC converter, battery management and direct micro/speaker control. The "arm-length hands-free" function and long battery life increase the comfort of cordless handsets. The talk time of a cordless handset is up to 15 hours, using standard 450 mA/h batteries, with more than a week of standby time.

The basestation chip supports different versions of CID and supports "hands-free" (in the basestation). The integrated CR16 RISC controller handles the software protocols and high end MMI. Customers can include a telephone answering machine by adding an external 32Mbit (15 minutes recording) Flash memory IC directly to the baseband. The CR16 will support the answering machine for two lines simultaneously. The basestation chip supports multiple handsets; up to two with a low cost 900MHz radio and up to nine with a high end 2.4GHz radio. Three typical types of systems with the same baseband chipset are:
• Basic model (1/4 bit-rate) with two handsets on a basestation
• Mid-range (1/2 bit-rate) with five handsets on a 1- or 2-line basestation
• High end (full bit-rate) with up to nine handsets on a 4-line basestation (with extra DSP chip)

National Semiconductor Corporation, 2900 Semiconductor Drive, P.O. Box 58090, Santa Clara, CA 95052-8090. Tel: 408-721-5000; Fax: 800-737-7018.