參數(shù)資料
型號： LM4838LQ/NOPB
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 音頻控制
英文描述： 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC28
封裝： LLP-28
文件頁數(shù)： 11/38頁
文件大?。?/td> 2351K
代理商： LM4838LQ/NOPB
Application Information (Continued)
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4838’s shutdown function. Activate micro-power shut-
down by applying V
DD to the SHUTDOWN pin. When active,
the LM4838’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.
There are a few ways to control the micro-power shutdown.
These include using a single-pole, single-throw switch, a
microprocessor, or a microcontroller. When using a switch,
connect an external 10k
pull-up resistor between the
SHUTDOWN pin and V
DD. Connect the switch between the
SHUTDOWN pin and ground. Select normal amplifier opera-
tion by closing the switch. Opening the switch connects the
SHUTDOWN pin to V
DD through the pull-up resistor, activat-
ing micro-power shutdown. The switch and resistor guaran-
tee that the SHUTDOWN pin will not float. This prevents
unwanted state changes. In a system with a microprocessor
or a microcontroller, use a digital output to apply the control
voltage to the SHUTDOWN pin. Driving the SHUTDOWN pin
with active circuitry eliminates the need for a pull up resistor.
MODE FUNCTION
The LM4838’s MODE function has 2 states controlled by the
voltage applied to the MODE pin. Mode 0, selected by
applying 0V to the MODE pin, forces the LM4838 to effec-
tively function as a "line-out," unity-gain amplifier. Mode 1,
which uses the internal DC controlled volume control is
selected by applying V
DD to the MODE pin. This mode sets
the amplifier’s gain according to the DC voltage applied to
the DC VOL CONTROL pin. Unanticipated gain behavior can
be prevented by connecting the MODE pin to V
DD or ground.
Note: Do not let the mode pin float.
MUTE FUNCTION
The LM4838 mutes the amplifier and DOCK outputs when
V
DD is applied to the MUTE pin. Even while muted, the
LM4838 will amplify a system alert (beep) signal whose
magnitude satisfies the BEEP DETECT circuitry. Applying
0V to the MUTE pin returns the LM4838 to normal, unmuted
operation. Prevent unanticipated mute behavior by connect-
ing the MUTE pin to V
DD or ground. Do not let the mute pain
float.
HP SENSE FUNCTION ( Head Phone In )
Applying a voltage between 4V and V
DD to the LM4838’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 3 shows the implementation of the LM4838’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 LM4838 into bridged mode op-
eration. 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 LM4838 operates
in bridged mode, the DC potential across the load is essen-
tially 0V. Therefore, even in an ideal situation, the output
swing cannot cause a false single-ended trigger. Connecting
headphones to the headphone jack disconnects the head-
phone jack contact pin from R2 and allows R1 to pull the HP
Sense pin up to V
DD through R4. This enables the head-
phone function, turns off both of the "+" output amplifiers,
and mutes the bridged speaker. The remaining single-ended
amplifiers then drive the headphones, whose impedance is
in parallel with resistors R2 and R3. These resistors have
negligible effect on the LM4838’s output drive capability
since the typical impedance of headphones is 32
.
Figure 3 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 1A
and 2A will drive a pair of headphones.
20013304
FIGURE 3. Headphone Sensing Circuit
LM4838
www.national.com
19
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參數(shù)描述
LM4838LQX/NOPB 功能描述:IC AMP AUDIO PWR 2.2W STER 28LLP 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，2-通道（立體聲） 在某負(fù)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)
LM4838MT 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2W SMD TSSOP28
LM4838MT/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，2-通道（立體聲） 在某負(fù)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)
LM4838MTE 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2.2W SMD TSSOP28
LM4838MTE/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，2-通道（立體聲） 在某負(fù)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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