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參數(shù)資料
| 型號： | LM4835MTE |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻控制 |
| 英文描述： | Stereo 2W Audio Power Amplifiers with DC Volume Control and Selectable Gain |
| 中文描述： | 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO28 |
| 封裝： | TSSOP-28 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 648K |
| 代理商： | LM4835MTE |
Application Information
(Continued)
BEEP DETECT FUNCTION
The Beep Detect pin (pin 11) is a mono input that detects the
presence of a beep signal. When a signal greater than
2.5V
(or 1/2 V
) is present at pin 11, the Beep Detect cir-
cuitry will enable the bridged amplifiers. Beep in signals less
than 2.5V
(or 1/2 V
) will not trigger the Beep Detect cir-
cuitry. When triggered, the Beep Detect circuitry will enable
the bridged amplifiers regardless of the state of the mute,
mode, or HP sense pins. As shown in the Fig. 2, a 200k
re-
sistor is placed in series with the input capacitor. This 200k
resistor can be changed to vary the amplitude of the beep in
signal. Higher values of the resistor will reduce the amplifier
gain and attenuate the beep in signal. These resistors are re-
quired in order for the beep signal to pass to the output. The
Beep Detect pin will not pass the beep signal to the output.
In cases where system beeps are required when the system
is in a suspended mode, the LM4835 must be brought out of
shutdown before the beep in signal is input.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4835 contains a shutdown pin to externally turn off the
bias circuitry. The LM4835 will shutdown when a logic high is
placed on the shutdown pin. The trigger point between a
logic low and logic high level is typically half supply. It is best
to switch between ground and the supply V
to provide
maximum device performance. By switching the shutdown
pin to V
, the LM4835 supply current draw will be mini-
mized. While the device will be disabled with shutdown pin
voltages less than V
, the idle current may be greater than
the typical value of 0.7 μA.The shutdown pin should not be
floated, since this may result in an unwanted shutdown con-
dition.
In many applications, a microcontroller or microprocessor
output is used to control the shutdown circuitry which pro-
vides a quick, smooth transition into shutdown.Another solu-
tion is to use a single-pole, single-throw switch in conjuction
with an external pull-up resistor. When the switch is
closed,the shutdown pin is connected to ground and enables
the amplifier. If the switch is open, then the external pull-up
resistor will shutdown the LM4835. This scheme prevents
the shutdown pin from floating.
MODE FUNCTION
The LM4835 was designed to operate in two modes. In
mode 0 (lineout mode),where the mode pin (pin 4) is given a
logic level low, the attenuation of the outputs are fixed at
unity gain. In mode 1 (adjustable mode), where the mode pin
is given a logic level high, the attenuation of the amplifier out-
puts is controlled through the DC voltage at pin 7.
MUTE FUNCTION
By placing a logic level high on the mute pin (pin5), the out-
puts of the amplifiers and pins 9 and 13 will be muted. The
beep in signal will be output even if the LM4835 is muted.
The mute pin must not be floated.
HP SENSE FUNCTION
The LM4835 possesses a headphone sense pin (pin 21) that
mutes the bridged amplifier, when given a logic high, so that
headphone or line out operation can occur while the bridged
connected load will be muted.
Figure 4 shows the implementation of the LM4835’s head-
phone control function using a single-supply. The voltage di-
vider of R1, R2, and R4 sets the voltage at the HP sense pin
(pin 21) to be approximately 50 mV when there are no head-
phones plugged into the system. This logic-low voltage at
the HP sense pin enables the bridged power amplifiers. Re-
sistor R4 limits the amount of current flowing out of the HP
sense pin when the voltage at that pin goes below ground re-
sulting from the music coming from the headphone amplifier.
Since the threshold of the HP sense pin is set at 4V ( or 80%
V
DD
), the output swing cannot cause false triggering.
When a set of headphones are plugged into the system, the
contact pin of the headphone jack is disconnected from the
signal pin, interrupting the voltage divider set up by resistors
R1, R2, and R4. Resistor R1 then pulls up the HP sense pin,
enabling the headphone function and disabling the bridged
amplifier. The headphone amplifier then drives the head-
phones, whose impedance is in parallel with resistor R2 and
R3. Also shown in Figure 4 are the electrical connections for
the headphone jack and plug.A3-wire plug consists of a Tip,
Ring and Sleeve, where the Tip and Ring are signal carrying
conductors and the Sleeve is the common ground return.
One control pin contact for each headphone jack is sufficient
to indicate that the user has inserted a plug into a jack and
that another mode of operation is desired.
The LM4835 can be used to drive both a bridged 8
internal
speaker and a pair of 32
speakers without using the HP
sense circuit. In this case the HP sense is controlled by a mi-
croprocessor or a switch.
GAIN SELECT FUNCTION (Bass Boost)
External gain/internal gain can be toggled by changing the
logic at pin 3. A logic high will switch the power amplifiers to
external gain mode. In external gain mode the gain of the
amplifier is set by the external resistors. Whereas the inter-
nal gain mode sets the amplifiers to unity gain.
In some cases a designer may want to improve the low fre-
quency response of the bridged amplifier or incorporate a
bass boost feature. This bass boost can be useful in systems
where speakers are housed in small enclosures. A resistor,
R
, and a capacitor, C
, in parallel, can be placed in se-
ries with the feedback resistor of the bridged amplifier as
seen in Figure 5
DS100139-4
FIGURE 4. Headphone Sensing Circuit
www.national.com
12
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM4835MTE/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，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4835MTEX/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，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4835MTX | 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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4835MTX/HALF | 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® 標準包裝:80 系列:- 類型:AB 類 輸出類型:1-通道（單聲道） 在某負載時最大輸出功率 x 通道數(shù)量:1.25W x 1 @ 8 歐姆 電源電壓:2.5 V ~ 5.5 V 特點:消除爆音，差分輸入，關閉，熱保護 安裝類型:表面貼裝 供應商設備封裝:8-MSOP-PowerPad 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:管件 配用:296-31419-ND - EVAL MODULE FOR TPA6205A1 其它名稱:296-34563-5TPA6205A1DGN-ND |
| LM4835MTX/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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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