Analog audio subsystem with integrated noise reduction from National Semiconductor

National Semiconductor introduced the PowerWise LM49155, an analog audio subsystem with integrated noise reduction for use in smartphones and full-featured phones. This device can improve the talker's voice-signal-to-background-noise ratio while retaining natural speech quality and thus giving phone users clear voice on both transmit and receive ends of the communications link. The LM49155 also increases the accuracy of voice recognition systems.

The LM49155 analog audio subsystem consumes only 3.7 mA of quiescent current for the earpiece amplifier and microphone amplifier signal path. The subsystem enables rapid integration of noise suppression performance in phone handsets, without the added development time required to write and test voice-processing programming code for a DSP or microprocessor.

The LM49155 provides uplink noise suppression and downlink signal-to-noise ratio (SNR) enhancement. The subsystem includes a 1.35W Class D speaker driver with automatic level control (ALC), ground-referenced headphone amplifier with click-pop suppression, and mixing and volume control. The LM49155's uplink noise suppression technology rejects far-field noise through a two-microphone amplifier implementation. Downlink voice intelligibility is improved by enhancing the SNR between the handset's earpiece signal level and the ambient noise level. The LM49155 preserves uplink near-field voice signals within close range, while rejecting acoustic noise more than 0.5 meters away from the microphones. In addition, the LM49155 provides continuous downlink signal adjustments so the caller's voice is always clearly heard regardless of the listener's environment.

National's latest noise suppression technology is also available in a discrete noise-processing IC, the LMV1099. It delivers 34 dB uplink far-field noise suppression at 1 kHz, near-field SNR enhancement of 6 dB to 18 dB, and downlink SNR improvement of 16 dB. The LMV1099 provides uplink and downlink total harmonic distortion plus noise (THD+N) of 0.1 percent, shutdown current at 0.07 uA, and supply current of 3.7 mA. The IC operates from a supply voltage range of 2.7V to 5.5V.

Package:
LM49155 comes in an ultra-small 36-bump micro SMD package measuring 3.4 mm by 3.4 mm.
LMV1099 comes in a 25-bump micro SMD package.

Price:
The LM49155 analog audio subsystem is priced at US$2.25 each for 1,000-unit quantities.
The LMV1099 noise-processing IC is priced at US$1.50 each for 1,000-unit quantities.

Availability: Now

For more information visit: www.national.com.