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参数资料
| 型号： | LM4841LQ/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频控制 |
| 英文描述： | 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC28 |
| 封装： | LLP-28 |
| 文件页数： | 11/31页 |
| 文件大小： | 1138K |
| 代理商： | LM4841LQ/NOPB |
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Application Information (Continued)
CAP-LESS HEADPHONE (SINGLE-ENDED) AMPLIFIER
OPERATION
An internal pullup circuit is connected to the HP Sense (Pin
21 HP-IN) headphone amplifier control pin. When this pin is
left unconnected, V
DD is applied to the HPIN. This turns off
Amp B +OUT (not seen in Fig 5, see Fig 2 Pin 15) and
switches Amp A +OUT’s input signal from an audio signal to
the V
DD/2 voltage present on pin 28 (Amp A + OUT). The
result is muted bridge-connected loads. Quiescent current
consumption is reduced when the IC is in this singleended
mode.
Figure 5 above shows the implementation of the LM4841’s
headphone control function. An internal comparator with a
nominal 400mV offset monitors the signal present at the
OUT B output. It compares this signal against the signal
applied to the HPIN pin (Notice in Figure 5, Pin 21 is
shorted to Pin 17 without a headphone plugged in). When
these signals are equal, as in the case when a BTL is
connected to the amplifier, an internal comparator forces the
LM4841 to maintain bridgedamplifier operation. When the
HPIN pin is externally floated, such as when headphones
are connected to the jack shown in Figure 5, an internal
pullup forces V
DD on the internal comparator’s HPIN in-
puts. This changes the comparator’s output state and en-
ables the headphone function: it turns off Amp B +OUT (not
seen in Fig 5, see Fig 2 Pin 15), switches the Amp A +OUT
input signal from an audio signal to the V
DD/2 DC voltage
present on pin 28, and mutes the bridge-connected loads.
Amp A -OUT and Amp B -OUT drive the headphones.
Figures 2 and 6 also show suggested headphone jack elec-
trical connections. The jack is designed to mate with a
threewire plug. The plug’s tip and ring should each carry
one of the two stereo output signals, whereas the sleeve
provides the return to Amp A +OUT. A headphone jack with
one control pin contact is sufficient to drive the HPIN pin
when connecting headphones
A switch can replace the headphone jack contact pin. When
a switch shorts the HPIN pin to V
DD (An open switch
contact will accomplish this because there is an internal
pull-up resistor), the bridgeconnected speakers are muted
and Amp A -OUT and Amp B -OUT drive the stereo head-
phones. When a switch shorts the HPIN pin to GND (pulling
down the internal pull-up resistor), the LM4841 operates in
bridge mode. If headphone drive is not needed, short the
HPIN pin to the OUTB pin.
ESD Protection
As stated in the Absolute Maximum Ratings, pin 28 on the
MT/MH packages and pin 25 on the LQ package, have a
maximum ESD susceptibility rating of 6500V. For higher
ESD voltages, the addition of a PCDN042 dual transil (from
California Micro Devices), as shown in Figure 6, will provide
additional protection.
GAIN SELECT FUNCTION (Bass Boost)
The LM4841 features selectable gain, using either internal or
external feedback resistors. Either set of feedback resistors
set the gain of the output amplifiers. The voltage applied to
the GAIN SELECT pin controls which gain is selected. Ap-
plying V
DD to the GAIN SELECT pin selects the external gain
mode. Applying 0V to the GAIN SELECT pin selects the
internally set unity gain.
In some cases a designer may want to improve the low
frequency 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
BA, and a capacitor, CBA, in parallel, can be placed in series
with the feedback resistor of the bridged amplifier as seen in
Figure 7.
20028094
FIGURE 6. The PCDN042 provides additional ESD protection beyond the 6500V shown in the
Absolute Maximum Ratings for the AMP2A output
LM4841
www.national.com
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4841MH | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive |
| LM4841MH/NOPB | 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4841MT | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Stereo 2W Amplifiers with DC Volume Control, Transient Free Outputs, and Cap-less Headphone Drive |
| LM4841MT/NOPB | 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4842 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Stereo 2W Amplifiers with DC Volume Control Transient Free Outputs, and Cap-less Headphone Drive |
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