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| 型号： | LM4674SQBD |
| 厂商： | National Semiconductor |
| 文件页数： | 4/27页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION LM4674SQ |
| 产品培训模块： | PowerWise® Products and Technology |
| 标准包装： | 1 |
| 系列： | Boomer® |
| 放大器类型： | D 类 |
| 输出类型： | 2 通道（立体声） |
| 在某负载时最大输出功率 x 通道数量： | 2.5W x 2 @ 4 欧姆 |
| 电源电压： | 2.4 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 板类型： | 完全填充 |
| 已用 IC / 零件： | LM4674 |
| 已供物品： | 板 |
| 相关产品： | LM4674SQX-ND - IC AMP AUDIO PWR 2.5W STER 16LLP LM4674SQ/NOPBDKR-ND - IC AMP AUDIO PWR 2.5W STER 16LLP LM4674SQ/NOPBCT-ND - IC AMP AUDIO PWR 2.5W STER 16LLP LM4674SQ/NOPBTR-ND - IC AMP AUDIO PWR 2.5W STER 16LLP |
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SNAS344E – DECEMBER 2005 – REVISED APRIL 2013
APPLICATION INFORMATION
GENERAL AMPLIFIER FUNCTION
The LM4674 stereo Class D audio power amplifier features a filterless modulation scheme that reduces external
component count, conserving board space and reducing system cost. The outputs of the device transition from
VDD to GND with a 300kHz switching frequency. With no signal applied, the outputs for each channel switch with
a 50% duty cycle, in phase, causing the two outputs to cancel. This cancellation results in no net voltage across
the speaker, thus there is no current to the load in the idle state.
With the input signal applied, the duty cycle (pulse width) of the LM4674 outputs changes. For increasing output
voltage, the duty cycle of the A output increases, while the duty cycle of the B output decreases for each
channel. For decreasing output voltages, the converse occurs. The difference between the two pulse widths
yields the differential output voltage.
DIFFERENTIAL AMPLIFIER EXPLANATION
As logic supplies continue to shrink, system designers are increasingly turning to differential analog signal
handling to preserve signal to noise ratios with restricted voltage signs. The LM4674 features two fully differential
amplifiers. A differential amplifier amplifies the difference between the two input signals. Traditional audio power
amplifiers have typically offered only single-ended inputs resulting in a 6dB reduction of SNR relative to
differential inputs. The LM4674 also offers the possibility of DC input coupling which eliminates the input coupling
capacitors. A major benefit of the fully differential amplifier is the improved common mode rejection ratio (CMRR)
over single ended input amplifiers. The increased CMRR of the differential amplifier reduces sensitivity to ground
offset related noise injection, especially important in noisy systems.
POWER DISSIPATION AND EFFICIENCY
The major benefit of a Class D amplifier is increased efficiency versus a class AB amplifier. The efficiency of the
LM4674 is attributed to the region of operation of the transistors in the output stage. The Class D output stage
acts as current steering switches, consuming negligible amounts of power compared to their Class AB
counterparts. Most of the power loss associated with the output stage is due to the IR loss of the MOSFET on-
resistance (RDS(ON)), along with switching losses due to gate charge.
SHUTDOWN FUNCTION
The LM4674 features independent left and right channel shutdown controls, allowing each channel to be
disabled independently. SDR controls the right channel, while SDL controls the left channel. Driving either low
disables the corresponding channel.
It is best to switch between ground and VDD for minimum current consumption while in shutdown. The LM4674
may be disabled with shutdown voltages in between GND and VDD, the idle current will be greater than the
typical 0.03A value. For logic levels between GND and VDD bypass SD_ with a 0.1μF capacitor.
The LM4674 shutdown inputs have internal pulldown resistors. The purpose of these resistors is to eliminate any
unwanted state changes when SD_ is floating. To minimize shutdown current, SD_ should be driven to GND or
left floating. If SD_ is not driven to GND or floating, an increase in shutdown supply current will be noticed.
SINGLE-ENDED AUDIO AMPLIFIER CONFIGURATION
The LM4674 is compatible with single-ended sources. When configured for single-ended inputs, input capacitors
must be used to block any DC component at the input of the device. Figure 5 shows the typical single-ended
applications circuit.
AUDIO AMPLIFIER POWER SUPPLY BYPASSING/FILTERING
Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass
capacitor as close to the device as possible. Typical applications employ a voltage regulator with 10F and 0.1F
bypass capacitors that increase supply stability. These capacitors do not eliminate the need for bypassing of the
LM4674 supply pins. A 1F capacitor is recommended.
12
Copyright 2005–2013, Texas Instruments Incorporated
Product Folder Links: LM4674
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4674SQX/NOPB | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4674TL | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Filterless 2.5W Stereo Class D Audio Power Amplifier |
| LM4674TL/NOPB | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4674TLBD | 功能描述:音频 IC 开发工具 LM4674 EVAL BOARD RoHS:否 制造商:Texas Instruments 产品:Evaluation Kits 类型:Audio Amplifiers 工具用于评估:TAS5614L 工作电源电压:12 V to 38 V |
| LM4674TLX | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
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