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參數(shù)資料
| 型號： | LM4849 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Stereo 2W Audio Power Amplifiers with DC Volume Control and Input Mux |
| 中文描述： | 立體聲2W的音頻功率放大器直流音量控制和輸入復(fù)用器 |
| 文件頁數(shù)： | 16/19頁 |
| 文件大?。?/td> | 690K |
| 代理商： | LM4849 |
Application Information
(Continued)
TABLE 1. Logic Level Truth Table for SHUTDOWN, HP-IN, and MUX Operation
SHUTDOWN
PIN
Logic Low
Logic Low
Logic Low
Logic Low
Logic High
HP-IN PIN
MUX CHANNEL
SELECT PIN
Logic Low
Logic High
Logic Low
Logic High
X
OPERATIONAL MODE
(MUX INPUT CHANNEL #)
Bridged Amplifiers (1)
Bridged Amplifiers (2)
Single-Ended Amplifiers (1)
Single-Ended Amplifiers (2)
Micro-Power Shutdown
Logic Low
Logic Low
Logic High
Logic High
X
MUTE FUNCTION
The LM4849 mutes the amplifier and DOCK outputs when
V
is applied to the MUTE pin. Applying 0V to the MUTE
pin returns the LM4849 to normal, unmated operation. Pre-
vent unanticipated mute behavior by connecting the MUTE
pin to V
DD
or ground. Do not let the mute pin float.
HP SENSE FUNCTION ( Head Phone In )
Applying a voltage between 4V and V
to the LM4849’s
HP-IN headphone control pin turns off the amps that drive
the left out "+" and right out "+" pins. This action mutes a
bridged-connected load. Quiescent current consumption is
reduced when the IC is in this single-ended mode.
Figure 2
shows the implementation of the LM4849’s head-
phone control function. With no headphones connected to
the headphone jack, the R1-R2 voltage divider sets the
voltage applied to the HP Sense pin at approximately 50mV.
This 50mV puts the LM4849 into bridged mode operation.
The output coupling capacitor blocks the amplifier’s half
supply DC voltage, protecting the headphones. (The HP-IN
threshold is set at 4V). While the LM4849 operates in
bridged mode, the DC potential across the load is essentially
0V. Therefore, even in an ideal situation, the output swing
cannot cause a false single-ended trigger. Connecting head-
phones to the headphone jack disconnects the headphone
jack contact pin from R2 and allows R1 to pull the HP Sense
pin up to V
through R4. This enables the headphone
function, turns off both of the "+" output amplifiers and mutes
the bridged speaker. The amplifier then drives the head-
phones, whose impedance is in parallel with resistors R2
and R3. These resistors have negligible effect on the
LM4849’s output drive capability since the typical impedance
of headphones is 32
.
Figure 2
also shows the suggested headphone jack electri-
cal connections. The jack is designed to mate with a three-
wire plug. The plug’s tip and ring should each carry one of
the two stereo output signals, whereas the sleeve should
carry the ground return. A headphone jack with one control
pin contact is sufficient to drive the HP-IN pin when connect-
ing headphones.
A microprocessor or a switch can replace the headphone
jack contact pin. When a microprocessor or switch applies a
voltage greater than 4V to the HP-IN pin, a bridge-connected
speaker is muted and the single ended output amplifiers will
drive a pair of headphones.
DC VOLUME CONTROL
The LM4849 has an internal stereo volume control whose
setting is a function of the DC voltage applied to the DC VOL
CONTROL pin.
The LM4849 volume control consists of 31 steps that are
individually selected by a variable DC voltage level on the
volume control pin. The range of the steps, controlled by the
DC voltage, are from 0dB - 78dB. Each gain step corre-
sponds to a specific input voltage range, as shown in table 2.
To minimize the effect of noise on the volume control pin,
which can affect the selected gain level, hysteresis has been
implemented. The amount of hysteresis corresponds to half
of the step width, as shown in Volume Control Characteriza-
tion Graph (DS200133-40).
For highest accuracy, the voltage shown in the ’recom-
mended voltage’ column of the table is used to select a
desired gain. This recommended voltage is exactly halfway
between the two nearest transitions to the next highest or
next lowest gain levels.
The gain levels are 1dB/step from 0dB to -6dB, 2dB/step
from -6dB to -36dB, 3dB/step from -36dB to -47dB, 4dB/step
from -47db to -51dB, 5dB/step from -51dB to -66dB, and
12dB to the last step at -78dB.
20076704
FIGURE 2. Headphone Sensing Circuit (MH Pinout)
L
www.national.com
16
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4849MH | Stereo 2W Audio Power Amplifiers with DC Volume Control and Input Mux |
| LM4852 | Integrated Audio Amplifier System |
| LM4852LQ | Integrated Audio Amplifier System |
| LM4852ITL | Integrated Audio Amplifier System |
| LM4854IBL | 1.9W Monaural, 85mW Stereo Headphone Audio Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4849MH | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Stereo 2W Audio Power Amplifiers with DC Volume Control and Input Mux |
| LM4849MH/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(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，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:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，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) |
| LM4849MHX/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(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，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:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，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) |
| LM4850 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Mono 1.5 W / Stereo 300 mW Power Amplifier |
| LM4850A E WAF | 制造商:Texas Instruments 功能描述: |
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