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參數(shù)資料
| 型號： | LM4855IBL |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Boomer AUDIO POWER AMPLIFIER Integrated Audio Amplifier System |
| 中文描述： | 1.1 W, 3 CHANNEL, AUDIO AMPLIFIER, PBGA18 |
| 封裝： | MICRO SMD-18 |
| 文件頁數(shù)： | 18/24頁 |
| 文件大?。?/td> | 1116K |
| 代理商： | LM4855IBL |
APPLICATION INFORMATION
(Continued)
voltage, increase the load impedance, or reduce the ambient
temperature. If these measures are insufficient, a heat sink
can be added to reduce
θ
. The heat sink can be created
using additional copper area around the package, with con-
nections to the ground pin(s), supply pin and amplifier output
pins. External, solder attached SMT heatsinks such as the
Thermalloy 7106D can also improve power dissipation.
When adding a heat sink, the
θ
is the sum of
θ
,
θ
CS
, and
θ
. (
θ
is the junction-to-case thermal impedance,
θ
is
the case-to-sink thermal impedance, and
θ
is the sink-to-
ambient thermal impedance.) Refer to the Typical Perfor-
mance Characteristics curves for power dissipation informa-
tion at lower output power levels.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. Applications that employ a 5V regulator typically
use a 10μF in parallel with a 0.1μF filter capacitors to stabi-
lize the regulator’s output, reduce noise on the supply line,
and improve the supply’s transient response. However, their
presence does not eliminate the need for a local 1.0μF
tantalum bypass capacitance connected between the
LM4855’s supply pins and ground. Keep the length of leads
and traces that connect capacitors between the LM4855’s
power supply pin and ground as short as possible. Connect-
ing a 1μF capacitor, C
, between the BYPASS pin and
ground improves the internal bias voltage’s stability and
improves the amplifier’s PSRR. The PSRR improvements
increase as the bypass pin capacitor value increases. 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
, depends on desired
PSRR requirements, click and pop performance (as ex-
plained in the section, Proper Selection of External Compo-
nents), system cost, and size constraints.
SELECTING EXTERNAL COMPONENTS
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value
input coupling capacitor (C
in Figure 2). A high 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 internal input resistor (R
i
) and the input capacitor (C
i
)
produce a high pass filter cutoff frequency that is found using
Equation (9).
f
c
= 1 / (2
π
R
i
C
i
)
(9)
As an example when using a speaker with a low frequency
limit of 150Hz, C
, using Equation (9) is 0.063μF. The 0.22μF
C
shown in Figure 1 allows the LM4855 to drive high effi-
ciency, full range speaker whose response extends below
40Hz.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consid-
eration should be paid to value of C
B
, the capacitor con-
nected to the BYPASS pin. Since C
determines how fast
the LM4855 settles to quiescent operation, its value is critical
when minimizing turn-on pops. The slower the LM4855’s
outputs ramp to their quiescent DC voltage (nominally V
/
2), the smaller the turn-on pop. Choosing C
equal to 1.0μF
along with a small value of C
i
(in the range of 0.1μF to
0.39μF), produces a click-less and pop-less shutdown func-
tion. As discussed above, choosing C
i
no larger than neces-
sary for the desired bandwidth helps minimize clicks and
pops. C
B
’s value should be in the range of 5 times to 7 times
the value of C
i
. This ensures that output transients are
eliminated when power is first applied or the LM4855 re-
sumes operation after shutdown.
L
www.national.com
18
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|---|---|
| LM4855LQ | Boomer AUDIO POWER AMPLIFIER Integrated Audio Amplifier System |
| LM4855ITL | Boomer AUDIO POWER AMPLIFIER Integrated Audio Amplifier System |
| LM4855 | Boomer AUDIO POWER AMPLIFIER Integrated Audio Amplifier System |
| LM4857 | Stereo 1.2W Audio Sub-system with 3D Enhancement |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4855IBL/NOPB | 功能描述:IC AMP AUDIO PWR 1.5W AB 18USMD 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，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，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) |
| LM4855ITL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述:IC AMP AUDIO 1W MONO SMD 4855 |
| LM4855ITL/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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4855ITLX | 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 1-CH Mono/2-CH Stereo 1.1W Class-AB 18-Pin uSMD T/R |
| LM4855ITLX/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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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