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參數(shù)資料
| 型號： | LM4839LQX/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻控制 |
| 英文描述： | 2 CHANNEL(S), TONE CONTROL CIRCUIT, CQCC28 |
| 封裝： | LLP-28 |
| 文件頁數(shù)： | 8/34頁 |
| 文件大?。?/td> | 1104K |
| 代理商： | LM4839LQX/NOPB |
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Application Information (Continued)
Higher value capacitors need more time to reach a quiescent
DC voltage (usually V
DD/2) when charged with a fixed cur-
rent. The amplifier’s output charges the input capacitor
through the feedback resistor, R
f. Thus, pops can be mini-
mized by selecting an input capacitor value that is no higher
than necessary to meet the desired 3dB frequency.
As shown in
Figure 1, the input resistors (RIN = 20K) and the
input capacitosr (CIN = 0.33F) produce a 6dB high pass
filter cutoff frequency that is found using Equation (7).
(7)
As an example when using a speaker with a low frequency
limit of 150Hz, the input coupling capacitor using Equation
(7), is 0.063F. The 0.33F input coupling capacitor shown
in
Figure 1 allows the LM4839 to drive high efficiency, full
range speaker whose response extends below 30Hz.
OPTIMIZING CLICK AND POP REDUCTION
PERFORMANCE
The LM4839 contains circuitry that minimizes turn-on and
shutdown transients or “clicks and pops”. For this discus-
sion, turn-on refers to either applying the power supply volt-
age or when the shutdown mode is deactivated. While the
power supply is ramping to its final value, the LM4839’s
internal amplifiers are configured as unity gain buffers. An
internal current source changes the voltage of the BYPASS
pin in a controlled, linear manner. Ideally, the input and
outputs track the voltage applied to the BYPASS pin. The
gain of the internal amplifiers remains unity until the voltage
on the bypass pin reaches 1/2 V
DD . As soon as the voltage
on the bypass pin is stable, the device becomes fully opera-
tional. Although the BYPASS pin current cannot be modified,
changing the size of C
B alters the device’s turn-on time and
the magnitude of “clicks and pops”. Increasing the value of
C
B reduces the magnitude of turn-on pops. However, this
presents a tradeoff: as the size of C
B increases, the turn-on
time increases. There is a linear relationship between the
size of C
B and the turn-on time. Here are some typical
turn-on times for various values of C
B:
C
B
T
ON
0.01F
2ms
0.1F
20ms
0.22F
44ms
0.47F
94ms
1.0F
200ms
DOCKING STATION
Applications such as notebook computers can take advan-
tage of a docking station to connect to external devices such
as monitors or audio/visual equipment that sends or receives
line level signals. The LM4839 has two outputs, Right Dock
and Left Dock which connect to outputs of the internal input
amplifiers that drive the volume control inputs. These input
amplifiers can drive loads of >1k
(such as powered speak-
ers) with a rail-to-rail signal. Since the output signal present
on the RIGHT DOCK and LEFT DOCK pins is biased to
V
DD/2, coupling capacitors should be connected in series
with the load. Typical values for the coupling capacitors are
0.33F to 1.0F. If polarized coupling capacitors are used,
connect their ’+’ terminals to the respective output pin.
Since the DOCK outputs precede the internal volume con-
trol, the signal amplitude will be equal to the input signal’s
magnitude and cannot be adjusted. However, the input am-
plifier’s closed-loop gain can be adjusted using external
resistors. These 20K resistors are shown in Figure 1 (RIN,
RF ) and they set each input amplifier’s gain to -1. Use
Equation 8 to determine the input and feedback resistor
values for a desired gain.
-A
v =RF /Ri
(8)
Adjusting the input amplifier’s gain sets the minimum gain for
that channel. Although the single ended outputs of the
Bridge Output Amplifiers can be used to drive line level
outputs, it is recommended that theR&L Dock Outputs
simpler signal path be used for better performance.
STEREO-INPUT MULTIPLEXER (STEREO MUX)
The LM4839 has two stereo inputs. The MUX CONTROL pin
controls which stereo input is active. Applying 0V to the MUX
CONTROL pin selects stereo input 1. Applying V
DD to the
MUX CONTROL pin selects stereo input 2.
BEEP DETECT FUNCTION
Computers and notebooks produce a system ’beep’ signal
that drives a small speaker. The speaker’s auditory output
signifies that the system requires user attention or input. To
accommodate this system alert signal, the LM4839’s beep
input pin is a mono input that accepts the beep signal.
Internal level detection circuitry at this input monitors the
beep signal’s magnitude. When a signal level greater than
V
DD/2 is detected on the BEEP IN pin, the bridge output
amplifiers are enabled. The beep signal is amplified and
applied to the load connected to the output amplifiers. A valid
beep signal will be applied to the load even when MUTE is
active. Use the input resistors connected between the BEEP
IN pin and the stereo input pins to accommodate different
beep signal amplitudes. These resistors are shown as
200k
devices in Figure 1. Use higher value resistors to
reduce the gain applied to the beep signal. The resistors
must be used to pass the beep signal to the stereo inputs.
The BEEP IN pin is used only to detect the beep signal’s
magnitude: it does not pass the signal to the output amplifi-
ers. The LM4839’s shutdown mode must be deactivated
before a system alert signal is applied to the BEEP IN pin.
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4839’s shutdown function. Activate micro-power shut-
down by applying V
DD to the SHUTDOWN pin. When active,
the LM4839’s micro-power shutdown feature turns off the
amplifier’s bias circuitry, reducing the supply current. The
logic threshold is typically V
DD/2. The low 0.7 A typical
shutdown current is achieved by applying a voltage that is as
near as V
DD as possible, to the SHUTDOWN pin. A voltage
that is less than V
DD may increase the shutdown current.
Logic Level Truth Table shows the logic signal levels that
activate and deactivate micro-power shutdown and head-
phone amplifier operation.
There are a few ways to control the micro-power shutdown.
These include using a single-pole, single-throw switch, a
LM4839
www.national.com
16
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4839MT | 制造商:Texas Instruments 功能描述:Stereo 1.1W Audio Amplifiers,LM4839MT |
| LM4839MT/NOPB | 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機，2-通道（立體聲） 在某負載時最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點:I²C，麥克風(fēng)，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4839MTBD | 功能描述:BOARD EVALUATION LM4839MT RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:1 系列:- |
| LM4839MTE | 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2.2W SMD TSSOP28 |
| LM4839MTE/NOPB | 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機，2-通道（立體聲） 在某負載時最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點:I²C，麥克風(fēng)，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
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