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參數(shù)資料
| 型號： | LM4913 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 2W Monaural, 90mW Stereo Headphone Audio Amplifier |
| 中文描述： | 2W的單聲道，立體聲耳機(jī)90兆瓦音頻放大器 |
| 文件頁數(shù)： | 12/15頁 |
| 文件大?。?/td> | 767K |
| 代理商： | LM4913 |
Application Information
(Continued)
muting it. The output coupling capacitors blocks the amplifi-
er’s half supply DC voltage, protecting the headphones from
the VDD/2 DC output voltage.
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 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.
SELECTING EXTERNAL COMPONENTS
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value
input coupling capacitor (Ci in Figure 2).Ahigh value capaci-
tor can be expensive and may compromise space efficiency
in portable designs. In many cases, however, the speakers
used in portable systems, whether internal or external, have
little ability to reproduce signals below 150Hz. Applications
using speakers with this limited frequency response reap
little improvement by using large input capacitor.
The LM4913’s advanced output transient suppression cir-
cuitry has eliminated the need to select the input capacitor’s
value in relation to the BYPASS capacitor’s value as was
necessary in some previous Boomer amplifiers. The value of
CI is now strictly determined by the desired low frequency
response.
As shown in Figure 2, the input resistor (Ri) and the input
capacitor (Ci) produce a high pass filter cutoff frequency that
is found using Equation (7).
f
C
= 1 / 2
π
R
i
C
i
As an example when using a speaker with a low frequency
limit of 150Hz, Ci, using Equation (7) is 0.063μF. The 1.0μF
Ci shown in Figure 2 allows the LM4913 to drive high effi-
ciency, full range speaker whose response extends below
30Hz.
(7)
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consid-
eration should be paid to value of CB, the capacitor con-
nected to the BYPASS pin. Since CB determines how fast
the LM4913 settles to quiescent operation, its value is critical
when minimizing turn-on pops. The slower the LM4913’s
outputs ramp to their quiescent DC voltage (nominally VDD/
2), the smaller the turn-on pop. Choosing CB equal to 1.0μF
along with a small value of Ci (in the range of 0.1μF to
0.39μF), produces a click-less and pop-less shutdown func-
tion. As discussed above, choosing Ci no larger than neces-
sary for the desired bandwidth helps minimize clicks and
pops. CB’s value should be in the range of 5 times to 7 times
the value of Ci. This ensures that output transients are
eliminated when power is first applied or the LM4913 re-
sumes operation after shutdown.
OPTIMIZING CLICK AND POP REDUCTION
PERFORMANCE
The LM4913 contains circuitry that eliminates turn-on and
shutdown transients ("clicks and pops") and transients that
could occur when switching between BTL speakers and
single-ended headphones. For this discussion, turn-on re-
fers to either applying the power supply voltage or when the
micro-power shutdown mode is deactivated.
As the VDD/2 voltage present at the BYPASS pin ramps to
its final value, the LM4913’s internal amplifiers are config-
ured as unity gain buffers and are disconnected from the
RO/MO+ and LO/MO- pins. An internal current source
charges the capacitor connected between the BYPASS pin
and GND in a controlled, linear manner. Ideally, the input and
outputs track the voltage applied to the BYPASS pin. The
gain of the internal amplifiers remains unity until the voltage
on the bypass pin reaches VDD/2.As soon as the voltage on
the bypass pin is stable, the device becomes fully opera-
tional and the amplifier outputs are reconnected to their
respective output pins. Although the BYPASS pin current
cannot be modified, changing the size of CB alters the
device’s turn-on time. There is a linear relationship between
the size of CB and the turn-on time. Here are some typical
turn-on times for various values of CB:
200617A2
FIGURE 4. Headphone Circuit
L
www.national.com
12
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4913MH | 2W Monaural, 90mW Stereo Headphone Audio Amplifier |
| LM4913MM | 2W Monaural, 90mW Stereo Headphone Audio Amplifier |
| LM4917 | Ground-Referenced, 95mW Stereo Headphone Amplifier |
| LM4917MT | Ground-Referenced, 95mW Stereo Headphone Amplifier |
| LM4917SD | Ground-Referenced, 95mW Stereo Headphone Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4913A WAF | 制造商:Texas Instruments 功能描述: |
| LM4913MH | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM4913MH/NOPB | 功能描述:IC AMP AUDIO MONO/STER 10TSSOP 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(jī)，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(hù)，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) |
| 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 制造商全稱:National Semiconductor 功能描述:2W Monaural, 90mW Stereo Headphone Audio Amplifier |
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