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参数资料
| 型号： | LM4913MH/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 0.09 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
| 封装： | TSSOP-10 |
| 文件页数： | 4/18页 |
| 文件大小： | 1078K |
| 代理商： | LM4913MH/NOPB |
regulator's output, reduce noise on the supply line, and im-
prove the supply's transient response. However, their pres-
ence does not eliminate the need for a local 0.47F tantalum
bypass capacitance connected between the LM4913's supply
pins and ground. Do not substitute a ceramic capacitor for the
tantalum. Doing so may cause oscillation.
Keep the length of leads and traces that connect capacitors
between the LM4913's power supply pin and ground as short
as possible. Connecting a 0.47F capacitor, C
B, between the
BYPASS pin and ground improves the internal bias voltage's
stability and improves the amplifier's PSRR. The PSRR im-
provements increase as the bypass pin capacitor value in-
creases. Too large, however, increases turn-on time and can
compromise the amplifier's click and pop performance. The
selection of bypass capacitor values, especially C
B, depends
on desired PSRR requirements, click and pop performance
(as explained in the section, Proper Selection of External
Components), system cost, and size constraints.
MICRO-POWER SHUTDOWN
The LM4913 features an active-low micro-power shutdown
mode. When active, the LM4913'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
0.1A typical shutdown current is achieved by applying a volt-
age to the SHUTDOWN pin that is as near to GND as possi-
ble. A voltage that is greater than GND may increase the
shutdown current.
There are a few methods to control the micro-power shut-
down. These include using a single-pole, single-throw switch
(SPST), a microprocessor, or a microcontroller. When using
a switch, connect a 100k
pull-up resistor between the
SHUTDOWN pin and V
DD and the SPST switch between the
SHUTDOWN pin and GND. Select normal amplifier operation
by opening the switch. Closing the switch applies GND to the
SHUTDOWN pin, activating micro-power shutdown. The
switch and resistor guarantee 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 active-state voltage to the SHUTDOWN pin.
HEADPHONE (SINGLE-ENDED) AMPLIFIER OPERATION
BTL/SE [Mono (BTL)/Stereo (SE)] Function
Applying a voltage greater than 0.9V
DD to the LM4913's BTL/
SE headphone control pin switches the amplifier's operation
from mono BTL to stereo SE. Applying a voltage less than
0.55V
DD to the LM4913's BTL/SE headphone control pin
switches the amplifier's operation from stereo SE to mono
BTL.
Figure 3 shows how to control the LM4913's headphone func-
tion using four external resistors and a dual-switch stereo
headphone jack. External resistors R4 - R6 provide the con-
trol voltages that are applied through the upper headphone
jack switch. R6 and R7 provide a DC return path for the SE
coupling capacitors.
200617a1
FIGURE 3. Headphone Operation and BTL - SE Mode Switching
With no headphones connected to the headphone jack, the
R5-R6 voltage divider sets the voltage applied to the BTL/SE
pin (pin 7) at approximately 50mV (comfortably below the
0.55V
DD logic-low threshold). This 50mV tells the LM4913 to
select the signal applied to the MONO-IN input and places the
LM4913 in mono BTL operation. When stereo SE operation
is desired, both headphone jack switches are opened with a
headphone plug. Opening the lower one, allows R5 to apply
V
DD to the BTL/SE pin. This switches the amplifier's inputs to
the stereo signal. Opening the lower one breaks the connec-
tion between AMP4's output and the BTL speaker, muting it.
The output coupling capacitors blocks the amplifier's half sup-
ply DC voltage, protecting the headphones from the V
DD/2 DC
output voltage.
Figure 3 also shows the suggested headphone jack electrical
connections. The jack is designed to mate with a three-wire
plug. The plug's tip and adjacent ring should carry the left and
right channel stereo signals, respectively. The sleeve furthest
from the tip should carry the ground return. The Switchcraft
35RAPC4BH3 five-terminal headphone jack easily satisfies
the LM4913's requirement for a dual switch headphone jack.
For applications that require an SPDIF interface in the stereo
headphone jack, use a Foxconn 2F1138-TJ-TR.
www.national.com
12
LM4913
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4913MHX/NOPB | 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 1-CH Mono/2-CH Stereo 2W Class-AB 10-Pin TSSOP EP T/R |
| LM4913MM | 制造商:NSC 制造商全称:National Semiconductor 功能描述:2W Monaural, 90mW Stereo Headphone Audio Amplifier |
| LM4914 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1W Monaural, 85mW Stereo Headphone Audio Amplifier |
| LM4914A WAF | 制造商:Texas Instruments 功能描述: |
| LM4914MH | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1W Monaural, 85mW Stereo Headphone Audio Amplifier |
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