One of the fastest growing Internet services is digital telephony. Better known as voice over Internet Protocol (VoIP), it lets users make phone calls over the Internet rather than through their usual telephone company connection.
With over 220 million subscribers worldwide, Skype is the largest VoIP service provider. In the U.S., the cable TV industry is the second major supplier of VoIP, with Vonage in second place. If you make a lot of phone calls, especially foreign calls, you can save big bucks with one of these services.
Skype has made VoIP cheap and easy to use, but you need to call from your PC or laptop. You need speakers and a microphone, of course, which are standard features in most new laptops. In older or newer computers, you can use a headset. Now, Winbond Electronics' W681308 audio controller will make it easy for vendors to create different forms of VoIP phones that can connect to your USB port.
According to the company, designers can use this single-chip Skype phone to create a USB phone handset, a USB cordless phone, a speaker phone, or even a headset. Other possibilities include a dual-mode USB/PSTN (public switched telephone network) phone, a USB analog telephone adapter (ATA), and a USB PSTN gateway.
The W681308 includes the voice codecs for conversion, an embedded controller, and a variety of interfaces. The codec uses 16-bit analog-todigital and digital-to-analog converters (ADCs and DACs) with selectable sampling rates of 8/16/48 kbits/s providing very high-quality audio.
Acoustic echo cancellation (AEC) and automatic gain control (AGC) support the speaker-phone application. Otherwise, full-duplex echo cancellation, a three-channel mixer, an integrated microphone amplifier, and a speaker driver are standard.
The 8051 embedded controller can run at 12/24/48 MHz and includes an 8-kbyte one-time programmable (OTP) ROM and 1-kbyte RAM. A full USB 2.0 interface is provided. A serial peripheral interface (SPI) supports external flash or an LCD, while a general-purpose I/O (GPIO) interface is available for a keyboard.
The chip does not include the usual voice compression and Simple Internet Protocol (SIP) typical of other VoIP voice chips. The W681308 puts the digitized voice into standard pulse code modulation (PCM) format at either 64 or 128 kbits/s and sends it by the USB port to the PC, where Skype software takes care of the compression and implements its special proprietary protocol.
The W681308 comes in a 48-pin leadless quad flat package (LQFP) and costs $1.80 in 10,000-unit quantities. A full software development kit with 8051-based Keil C development system is also available.
Winbond Electronic Corporation of America www.winbond-usa.com
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