National Semiconductor has announced the LM49155 analog audio subsystem with integrated noise reduction for mobile phones and other portable handheld applications. Designed to maintain voice quality in noisy environments while using minimum power consumption, the device enables the rapid integration of noise suppression performance in phone handsets.
The device combines a noise suppression microphone amplifier, a 1.35-W mono class-D amplifier with ALC, a class-AB earpiece driver with AGC, a high-efficiency, stereo, ground-referenced headphone amplifier with click/pop suppression and I2 C mode select and volume control. Quiescent current consumption is 3.7 mA for the earpiece amplifier and microphone amplifier signal path.
The LM49155's uplink noise suppression technology rejects far-field noise at 34 dB at 1 kHz through a two-microphone amplifier implementation. Downlink voice intelligibility is improved by enhancing the SNR (by 16 dB typ) between the handset's earpiece signal level and the ambient noise level.
The LM49155 is packaged in a 36-bump micro SMD package measuring 3.4 x 3.4 mm. Pricing is $2.25 each in 1,000-unit quantities.