NS LM49151音频子系统应用方案

NS 公司的LM49151是全集成的音频子系统,设计用于手持设备如手机等. LM49151集成了1.25W单声道E2S D类放大器,125mW AB类耳机驱动器,每路42mW的参考地耳机驱动器,音量控制,输入混合器/复用器以及扬声器保护等. LM49151主要用于手机,PDA,笔记本电脑,MP3播放器和手提电子设备.本文介绍了LM49151的主要特性和指标以及方框图与典型应用电路图.

The LM49151 is a fully integrated audio subsystem designed for portable handheld applications such as cellular phones.

The LM49151 combines a 1.25W mono E2S class D amplifier, 125mW Class AB earpiece driver, 42mW/channel stereo ground referenced headphone drivers, volume control, input
mixer/multiplexer, and speaker protection into a single device.

The LM49151 class D speaker amplifier features National’s unique Automatic Level Control (ALC) that provides both a I2C programmable no-clip feature with Clip Controls and speaker protection. The E2S (Enhanced Emission Suppression) class D amplifier features a patented, ultra low EMI PWM architecture that significantly reduces RF  emissions while preserving audio quality and efficiency while delivering 1.25W into an 8Ω load with <1% THD+N with a 5V supply.

The 42mW/channel headphone drivers feature National’s ground referenced architecture that creates a ground-referenced output from a single supply, eliminating the need for bulky and expensive DC-blocking capacitors, saving space and minimizing system cost.

The LM49151 features separate volume controls for the loudspeaker and headphone inputs. Mode selection, shutdown control, and volume are controlled through an I2C compatible interface. The LM49151s superior click and pop suppression eliminates audible transients on power-up/down and during shutdown.

LM49151主要指标:

Output power at VDD = 3.3V THD+N ≤ 1%

LS Mode, RL = 8Ω 520mW (typ)

HP Mode, RL = 32Ω 40mW (typ)

Output power at VDD = 5V THD+N ≤ 1%

LS Mode, RL = 8Ω 1.25W (typ)

HP Mode, RL = 32Ω 42mW (typ)

Output Offset

LS Mode 15 6mV (typ)

HP Mode 15 2mV (typ)

LM49151主要特性:

E2S class D amplifier

Ground referenced outputs — eliminates output coupling capacitors

I2C programmable No Clip Function with Clip Control

Voltage limiter speaker protection

I2C volume and mode Control

Ear Piece Amplifier

Advanced click-and-pop suppression

Low supply current

Micro-power shutdown

20-bump micro SMD package

LM49151应用:

Mobile Phones

PDAs

Notebook PCs

Portable Electronics Devices

MP3 Players



图1.LM49151T方框图和典型应用电路图