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參數(shù)資料
| 型號： | LM4923LQ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
| 中文描述： | 1.1 W, 1 CHANNEL, AUDIO AMPLIFIER, QCC8 |
| 封裝： | LLP-8 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 433K |
| 代理商： | LM4923LQ |
Typical Performance Characteristics
(Continued)
Output Power vs Load Resistance
Supply Current Shutdown Voltage
20071327
20071328
Application Information
DIFFERENTIAL AMPLIFIER EXPLANATION
The LM4923 is a fully differential audio amplifier that fea-
tures differential input and output stages. Internally this is
accomplished by two circuits: a differential amplifier and a
common mode feedback amplifier that adjusts the output
voltages so that the average value remains V
DD
/ 2. When
setting the differential gain, the amplifier can be considered
to have "halves". Each half uses an input and feedback
resistor (R
i1
and R
F1
) to set its respective closed-loop gain
(see Figure 1). With R
i1
= R
i2
and R
F1
= R
F2
, the gain is set
at -R
F
/ R
i
for each half. This results in a differential gain of
A
VD
= -R
F
/R
i
(1)
It is extremely important to match the input resistors to each
other, as well as the feedback resistors to each other for best
amplifier performance. See the
Proper Selection of Exter-
nal Components
section for more information. A differential
amplifier works in a manner where the difference between
the two input signals is amplified. In most applications, this
would require input signals that are 180 out of phase with
each other. The LM4923 can be used, however, as a single
ended input amplifier while still retaining its fully differential
benefits. In fact, completely unrelated signals may be placed
on the input pins. The LM4923 simply amplifies the differ-
ence between them.
All of these applications provide what is known as a "bridged
mode" output (bridge-tied-load, BTL). This results in output
signals at V
o1
and V
o2
that are 180 out of phase with
respect to each other. Bridged mode operation is different
from the single-ended amplifier configuration that connects
the load between the amplifier output and ground. A bridged
amplifier design has distinct advantages over the single-
ended configuration: it provides differential drive to the load,
thus doubling maximum possible output swing for a specific
supply voltage. Four times the output power is possible
compared with a single-ended amplifier under the same
conditions. This increase in attainable output power as-
sumes that the amplifier is not current limited or clipped. In
order to choose an amplifier’s closed-loop gain without caus-
ing excess clipping, please refer to the
Audio Power Am-
plifier Design
section.
A bridged configuration, such as the one used in the
LM4923, also creates a second advantage over single-
ended amplifiers. Since the differential outputs, V
o1
and V
o2
,
are biased at half-supply, no net DC voltage exists across
the load. This assumes that the input resistor pair and the
feedback resistor pair are properly matched (see
Proper
Selection of External Components
). BTL configuration
eliminates the output coupling capacitor required in single-
supply, single-ended amplifier configurations. If an output
coupling capacitor is not used in a single-ended output con-
figuration, the half-supply bias across the load would result
in both increased internal IC power dissipation as well as
permanent loudspeaker damage. Further advantages of
bridged mode operation specific to fully differential amplifiers
like the LM4923 include increased power supply rejection
ratio, common-mode noise reduction, and click and pop
reduction.
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS
The LM4923’s exposed-DAP (die attach paddle) package
(LLP) provide a low thermal resistance between the die and
the PCB to which the part is mounted and soldered. This
allows rapid heat transfer from the die to the surrounding
PCB copper traces, ground plane and, finally, surrounding
air. Failing to optimize thermal design may compromise the
LM4923’s high power performance and activate unwanted,
though necessary, thermal shutdown protection. The LLP
package must have its DAP soldered to a copper pad on the
PCB. The DAP’s PCB copper pad is connected to a large
plane of continuous unbroken copper. This plane forms a
thermal mass and heat sink and radiation area. Place the
heat sink area on either outside plane in the case of a
two-sided PCB, or on an inner layer of a board with more
than two layers. Connect the DAP copper pad to the inner
layer or backside copper heat sink area with a thermal via.
L
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4923LQ/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 |
| LM4923LQBD | 功能描述:音頻 IC 開發(fā)工具 LM4923LQ EVAL BOARD RoHS:否 制造商:Texas Instruments 產(chǎn)品:Evaluation Kits 類型:Audio Amplifiers 工具用于評估:TAS5614L 工作電源電壓:12 V to 38 V |
| LM4923LQBD/NOPB | 制造商:Texas Instruments 功能描述:Evaluation Kit For 1.1 Watt Fully Differential Audio Power Amplifier With Shut-Down Select |
| LM4923LQX | 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 |
| LM4923LQX/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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