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參數(shù)資料
| 型號(hào)： | LM4936 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Stereo 2W Audio Power Amplifiers with Volume Control and Selectable Control Interface (SPI or I2C) |
| 中文描述： | 2W的立體聲音頻功率放大器，帶有音量控制和可選控制接口（SPI或I2C） |
| 文件頁數(shù)： | 20/28頁 |
| 文件大?。?/td> | 1490K |
| 代理商： | LM4936 |
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Application Information
(Continued)
C
B
0.01μF
0.1μF
0.22μF
0.47μF
1.0μF
T
ON
2ms
20ms
44ms
94ms
200ms
DOCKING STATION INTERFACE
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 LM4936 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
/2, coupling capacitors should be connected in series
with the load when using these outputs. Typical values for
the output coupling capacitors are 0.33μF to 1.0μF. If polar-
ized coupling capacitors are used, connect their "+" termi-
nals to the respective output pin, see
Figure 2
.
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
(R
, R
) are shown in
Fig-
ure 2
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
VR
= R
DOCK1
/R
IN1
and - A
VL
= R
DOCK2
/R
IN2
Adjusting the input amplifier’s gain sets the minimum gain for
that channel. Although the single ended output of the Bridge
Output Amplifiers can be used to drive line level outputs, it is
recommended that the R & L Dock Outputs simpler signal
path be used for better performance.
(8)
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 LM4936’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
/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.Avalid
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 (R
) are shown
as 200k
values in
Figure 2
. 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 LM4936’s shutdown mode must be deactivated
before a system alert signal is applied to BEEP IN pin.
MICRO-POWER SHUTDOWN
Shutdown mode is activated when a digital 0 is loaded into
the Shutdown bit, B0. When active, the LM4936’s micro-
power shutdown feature turns off the amplifier’s bias circuitry
reducing supply current to a typical 0.7μA. Loading a digital
1 into B0 disables shutdown mode. When the LM4936 has
power applied, all register bits will have a default value of 0.
Because of this, the LM4936 will be in shutdown mode when
power is applied.
MODE FUNCTION
The LM4936’s Mode function has two states controlled by bit
B2. A digital 0 in bit B2 disables the volume control and
forces the LM4936 to function as a fixed gain amplifier. The
gain selection is determined by the GAIN SEL bit (B3) While
in the fixed gain mode the volume setting has no effect on
the output. When a digital 1 is loaded into B2 the output level
is determined by the volume control bits. See Table 4 for
volume settings.
MUTE FUNCTION
The LM4936 mutes the amplifier and DOCK outputs when a
digital 1 is loaded in bit B1. Even while muted, the LM4936
will amplify a system alert (beep) signal whose magnitude
satisfies the BEEP DETECT circuitry. Loading a digital 0 into
B1 returns the LM4936 to normal operation.
HP SENSE FUNCTION ( Headphone In )
Applying a voltage between the V
IH
threshold shown in the
graph found in the Typical Performance Characteristics and
V
to the LM4936’s HP SENSE control pin or loading a
digital 1 into the HP Control bit (B4) will change the output
mode. The ’+’ outputs will change to be in phase with the ’-’
outputs instead of 180 degrees out of phase. This action
mutes a bridged-connected load since the differential volt-
age across the load is now close to 0V. The HP SENSE pin
over rides the HP Control bit. See Table 2 for more info.
Quiescent current consumption is reduced when the IC is in
this single-ended mode.
Figure 3 shows the implementation of the LM4936’s head-
phone control function. With no headphones connected to
the headphone jack, the R1-R2 voltage divider sets the
20117805
FIGURE 3. Headphone Sensing Circuit
L
www.national.com
20
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PDF描述 |
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| LM4980 | 2 Cell Battery, 1mA, 42mW Per Channel High Fidelity Stereo Headphone Audio Amplifier for MP3 players |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM49360 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Mono Class D Audio Codec PMU with Ground Referenced Headphone Amplifiers, Earpiece Driver, Audio DSP, 2 Step-Down DC-DC Converters, and 7 LDO Regulators |
| LM49360RL | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Mono Class D Audio Codec PMU with Ground Referenced Headphone Amplifiers, Earpiece Driver, Audio DSP, 2 Step-Down DC-DC Converters, and 7 LDO Regulators |
| LM49360RLX | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Mono Class D Audio Codec PMU with Ground Referenced Headphone Amplifiers, Earpiece Driver, Audio DSP, 2 Step-Down DC-DC Converters, and 7 LDO Regulators |
| LM4936MH | 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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4936MH/NOPB | 功能描述:音頻放大器 Stereo 2W Audio Pwr Amp 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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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