Uplink noise suppression & downlink SNR enhancement analog audio subsystem

The LM49155 is a fully integrated audio subsystem designed for portable handheld applications such as cellular phones. The

LM49155 combines a Noise Suppression microphone amplifier, a 1.35W mono class D amplifier with ALC, class AB earpiece driver

with AGC, a high efficiency, stereo, ground referenced headphone amplifier with click pop suppression and I

2C modes select and volume control.

The LM49155 features analog fully differential input, and differential output microphone amplifier designed to reduce background

acoustic noise, while delivering superb speech clarity in voice communication applications. Downlink SNR enhancement with

an advanced acoustic AGC technology to adjust output levels.

The LM49155 speaker amplifier features National’s unique output limiter that provides both a no-clip feature and speaker protection.

The E

2S class D amplifier features a patented, ultra low EMI PWM architecture that significantly reduces RF emissions while preserving

audio quality and efficiency. The headphone drivers feature National’s ground referenced architecture that creates a ground-referenced

output from a single, low-voltage supply.

The LM49155 is available in an ultra-small 36-bump micro SMD package (3.434mm x 3.459mm x 0.6mm).

Notice: This document is not a full datasheet. For more information regarding this product or to order samples please contact

your local National Semiconductor sales office or visit http://www.national.com/support/dir.html

Key Specifications

■

 Uplink Far Field Noise Suppression

 Electrical FFNSE at f = 1kHz

34dB (typ)

■

 Downlink SNR Enhancement Earpiece Amplifier

  Near-Field SNR Enhancement

 Downlink SNRIE

6 to 18dB (typ)

16dB (typ)

■

 Class D Loudspeaker Amplifier RL = 15μH+8Ω+15μH

 POUT, THD+N

≤ %, VDD = 5.0V

1.35W (typ)

■

 Headphone Amplifier RL = 32Ω

 POUT, THD+N

≤ %, HPVDD = 1.8V

19mW (typ)