參數(shù)資料
型號(hào)： LM4841
廠商： National Semiconductor Corporation
英文描述： Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive
中文描述： 2W的立體聲放大器直流音量控制，瞬態(tài)自由輸出，無(wú)電容耳機(jī)驅(qū)動(dòng)器
文件頁(yè)數(shù)： 14/31頁(yè)
文件大小： 1138K
代理商： LM4841
Application Information
ELIMINATING OUTPUT COUPLING CAPACITORS
Typical single-supply audio amplifiers that can switch be-
tween
driving
bridge-tied-load
single-ended (SE) headphones use a coupling capacitor on
each SE output. This capacitor blocks the half-supply volt-
age to which the output amplifiers are typically biased and
couples the audio signal to the headphones. The signal
return to circuit ground is through the headphone jack’s
sleeve.
The LM4841 eliminates these coupling capacitors. Amplifi-
erA+ (pin 28 on MT/MH) is internally configured to apply
V
DD
/2 to a stereo headphone jack’s sleeve. This voltage
matches the quiescent voltage present on theAmpAout- and
AmpBout- outputs that drive the headphones. The head-
phones
operate
in
a
manner
bridge-tied-load (BTL). The same DC voltage is applied to
both headphone speaker terminals. This results in no net DC
current flow through the speaker. AC current flows through a
headphone speaker as an audio signal’s output amplitude
increases on the speaker’s terminal.
When operating as a headphone amplifier, the headphone
jack sleeve is not connected to circuit ground. Using the
headphone output jack as a line-level output will place the
(BTL)
speakers
and
very
similar
to
a
LM4841’s one-half supply voltage on a plug’s sleeve con-
nection.
Driving
a
portable
audio-visual display equipment is possible. This presents no
difficulty when the external equipment uses capacitively
coupled inputs. For the very small minority of equipment that
is DC-coupled, the LM4841 monitors the current supplied by
the amplifier that drives the headphone jack’s sleeve. If this
current exceeds 500mA
PK
, the amplifier is shutdown, pro-
tecting the LM4841 and the external equipment.
notebook
computer
or
OUTPUT TRANSIENT (’POPS AND CLICKS’)
ELIMINATED
The LM4841 contains advanced circuitry that eliminates out-
put transients (’pop and click’). This circuitry prevents all
traces of transients when the supply voltage is first applied,
when the part resumes operation after shutdown, or when
switching between BTL speakers and SE headphones. Two
circuits combine to eliminate pop and click. One circuit
mutes the output when switching between speaker loads.
Another circuit monitors the input signal. It maintains the
muted condition until there is sufficient input signal magni-
tude (
>
22mV
, typ) to mask any remaining transient that
may occur. (See Turn On Characteristics).
Figure 3 shows the LM4841’s lack of transients in the differ-
ential signal (Trace B) across a BTL 8
load. The LM4841’s
active-high SHUTDOWN pin is driven by the logic signal
shown in Trace A. Trace C is the VOUT- output signal and
trace D is the VOUT+ output signal. The shutdown signal
frequency is 1Hz with a 50% duty cycle. Figure 4 is gener-
ated with the same conditions except that the output drives a
32
single-ended (SE) load. Again, no trace of output tran-
sients on Trace B can be observed.
20028095
FIGURE 3. Differential output signal (Trace B) is devoid of transients. The SHUTDOWN pin is driven by a shutdown
signal (Trace A). The inverting output (Trace C) and the non-inverting output (Trace D) are applied across an 8
BTL
load.
L
www.national.com
14
相關(guān)PDF資料
PDF描述
LM4841LQ Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive
LM4841MH Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive
LM4841MT Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive
LM4842 Stereo 2W Amplifiers with DC Volume Control Transient Free Outputs, and Cap-less Headphone Drive
LM4842LQ Stereo 2W Amplifiers with DC Volume Control Transient Free Outputs, and Cap-less Headphone Drive
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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LM48410SQBD 功能描述:音頻 IC 開(kāi)發(fā)工具 LM48410 EVAL BOARD RoHS:否 制造商:Texas Instruments 產(chǎn)品:Evaluation Kits 類型:Audio Amplifiers 工具用于評(píng)估:TAS5614L 工作電源電壓:12 V to 38 V
LM48410SQE/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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