LM4935 Integration in New Micro SMDxt Package Saves Up to 70 Percent Board Space
The industry’s smallest audio subsystem with a mono Class D speaker driver from National Semiconductor integrates all the analog and digital audio functions needed for smart phones and voice-over-Internet protocol (VoIP) phones. In a related announcement today, National released additional details of the subsystem’s new 4 mm by 4 mm micro SMDxt package, which saves up to 70 percent board space over existing packages. A member of the Boomer® audio power amplifier family, the LM4935 subsystem provides high-quality output power with a minimal number of external components.
Key Technical Features and Benefits
The LM4935 is a complete audio subsystem with multiple digital and analog inputs and outputs. Operating on supplies ranging from 1.8V to 5.5V, the LM4935 combines several features: a Class D speaker amplifier delivering 570 mW into an 8-Ohm load; a stereo headphone amplifier that supports output capacitor-less (OCL) or AC-coupled operation delivering 30 mW per channel into a 32-Ohm; a mono earpiece amplifier delivering 30 mW into a 32-Ohm load; and a line output for an external-powered handsfree speaker providing filter-less Class D stereo speaker capability. Other features include a successive approximation register (SAR) analog-to-digital converter (ADC) for system monitoring and a high-fidelity digital-to-analog converter.
The LM4935’s bi-directional I2S digital interface with pulse-code modulation (PCM) capability transmits any audio file or voice data transmission back and forth from the baseband application-specific integrated circuit (ASIC) or processor to the analog outputs. The subsystem also features a read/write I2C compatible digital interface.
In addition, the LM4935 gives engineers design flexibility in arranging analog inputs through a sophisticated switching/mixing circuitry, eliminating the need for external audio switches and mixing components. Two analog inputs allow the LM4935 to accept a stereo signal from an FM radio or operate as two separate mono inputs that can accept other analog input signals. Additional analog inputs allow for differential mono input and output from a GSM, CDMA or other cell phone radio module as well as a baseband application-specific integrated circuit (ASIC). Two additional inputs support internal and external microphone capability.
Innovative, Advanced 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.
National produces billions of chips per year and packages them in more than 70 different package types. The company has more than 290 patents in package technologies and receives approximately 30 new packaging patents each year. National has introduced several packaging innovations to the industry, including both the micro SMD and LLP® packaging technologies.
Pricing and Availability
Available now in a 49-bump micro SMDxt package, the LM4935 is priced at $3.95 each in 1,000-unit quantities.
