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| 型號： | LM4674TL/NOPB |
| 廠商： | National Semiconductor |
| 文件頁數(shù)： | 4/27頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC AMP AUDIO PWR 2.5W D 16USMD |
| 產(chǎn)品培訓(xùn)模塊： | PowerWise® Products and Technology |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 系列： | Boomer® |
| 類型： | D 類 |
| 輸出類型： | 2 通道（立體聲） |
| 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量： | 2.5W x 2 @ 4 歐姆 |
| 電源電壓： | 2.4 V ~ 5.5 V |
| 特點(diǎn)： | 消除爆音，差分輸入，PWM，短路保護(hù)，關(guān)機(jī) |
| 安裝類型： | 表面貼裝 |
| 供應(yīng)商設(shè)備封裝： | 16-uSMD |
| 封裝/外殼： | 16-WFBGA |
| 包裝： | 標(biāo)準(zhǔn)包裝 |
| 其它名稱： | LM4674TLDKR |
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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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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4674TLX | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM4674TLX/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4675 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Ultra-Low EMI, Filterless, 2.65W, Mono, Class D Audio Power Amplifier with Spread Spectrum |
| LM4675SD | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Ultra-Low EMI, Filterless, 2.65W, Mono, Class D Audio Power Amplifier with Spread Spectrum |
| LM4675SD/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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