TI(NS) 公司的LM48901是四路音頻D類功率放大器,輸出級采用前沿速率恐怖行動(ERC)PWM架構,能降低RF輻射而維持音頻質量和效率,它的I2S接口和標準串行音頻接口兼容,差分輸入立體聲ADC,平行輸出模式,RL = 8Ω, THD+N ≤10%時的輸出功率為1.7W ,RL = 4Ω, THD+N ≤10%時為2.8W (typ),而典型的THD+N為0.06%,主要用在便攜式計算機,平板電腦,臺式電腦,條形音箱,多媒體設備,MP3播放器附件和塢站.本文介紹了LM48901主要特性和指標,音頻放大器應用電路,通路音頻放大器應用電路和I2C_EN/I2C_EX菊花鏈案例應用電路以及評估板主要特性.
The LM48901 is a quad Class D amplifier that utilizes National’s proprietary spatial sound processor to create an enhanced sound stage for portable multimedia devices. The Class D output stages feature National’s edge rate control (ERC) PWM architecture that significantly reduces RF emissions while preserving audio quality and efficiency.
The LM48901’s flexible I 2S interface is compatible with standard serial audio interfaces. A stereo differential-input ADC gives the device the ability to process analog stereo audio signals.
The LM48901 is configured through an I 2C compatible interface and is capable of delivering 2.8W/channel of continuous output power into an 4Ω load with less than 10% THD+N. A 2.1 mode pairs two output drivers in parallel, increasing current drive for 4Ω loads.
Output short circuit and thermal overload protection prevent the device from being damaged during fault conditions. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown. The LM48901 is available in space saving microSMD and LLP packages.
LM48901 主要特性:
Spatial Sound Processing
I 2S Compatible Input
Differential-Input Stereo ADC
Edge Rate Control Reduces EMI while Preserving Audio Quality and Efficiency
Paralleled Output Mode
Short Circuit and Thermal Overload Protection
Minimum external components
Click and Pop suppression
Micro-power shutdown
Available in space-saving micro SMD and LLP packages
LM48901 應用:
Laptops
Tablets
Desktop Computers
Sound Bars
Multimedia Devices
MP3 Player Accessories
Docking Stations
LM48901 主要指標:
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■ SNR (A-Weighted)
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87dBA (typ)
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■ Output Power/channel, PVDD = 5V
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RL = 8Ω, THD+N ≤10%
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1.7W (typ)
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RL = 4Ω, THD+N ≤10%
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2.8W (typ)
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■ THD+N
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0.06% (typ)
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■ Efficiency/Channel
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89% (typ)
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■ PSRR at 217Hz
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71dB (typ)
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■ Shutdown current
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1μA (typ)
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圖1.LM48901典型音頻放大器應用電路
圖2.LM48901通路音頻放大器應用電路
圖3.LM48901 I2C_EN/I2C_EX菊花鏈案例應用電路
The LM49801 evaluation board accepts three audio input formats: stereo differential analog, SPDIF, or I2S. Multiple boards are easily cascaded, increasing the number of channels. The LM48901 can also be configured as a 2.1 amplifier for stereo + subwoofer applications.
The board is controlled though a Windows- and Mac OSX-compatible graphic user interface (GUI). The GUI configures the device, loads spatial coefficients, and provides a graphic equalizer. The board connects to a computer through a USB interface device (included).
System Components
Evaluation system hardware
LM49801SQ Evaluation Board
USB to I2C Interface
圖4.LM49801評估板外形圖
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