National Semiconductor introduced the LM4934 Boomer stereo audio subsystem to incorporate both digital and analog input paths for multimedia, smart and voice-over-Internet procotol (VoIP) phones. The LM4934 audio subsystem integrates audio amplifiers, volume control, a mixer, power management control and National’s 3D stereo sound-enhancement technology into a new, 3.3 mm by 3.9 mm, 42-bump micro SMDxt package. The 3D capability makes it easier for listeners to hear music more clearly through the phone by broadening the sound field of the closely placed speakers.

Key Technical Features

The LM4934 offers an I2S digital input and three analog inputs, which eliminate the need for an external digital-to-analog converter (DAC) and a multiplexer integrated circuit. Operating on a 3.3V supply, the single-chip LM4934 combines a stereo speaker amplifier delivering 500 mW typical per channel into an 8-Ohm load and a stereo headphone amplifier delivering 30 mW typical per channel into a 32-Ohm load. The chip features a 25 mW mono earpiece output and a separate line out to drive external audio devices. The on-board phased-lock loop (PLL) simplifies the customer’s selection of a clock frequency (from 8 MHz to 24 MHz) and saves cost by eliminating the need for an external crystal oscillator. The entire chip is controlled through 25 separate I2C compatible registers for maximum flexibility of routing inputs and outputs through the two-wire interface. In addition, the LM4934 routes and mixes the stereo and mono inputs into multiple, distinct output modes using a simple I2C compatible interface.

Packaging

National’s new micro SMDxt package provides high input/output analog devices with the smallest possible footprint for any given pin count. The micro SMDxt, which builds on the success of National’s micro SMD package, utilizes a unique solder ball structure that enables high-reliability products with bump counts up to 100 bumps at a 0.5 mm pitch. With the new package, reliability requirements for typical portable applications such as thermal cycling, thermal shock, drop test and flex test can be met without the use of an underfill.

Pricing and Availability

The LM4934, available now in a standard 42-bump micro SMDxt package, is priced at $3.80 in 1,000-unit quantities. A lead-free package will be available in early 2006.