參數(shù)資料
型號： LM4839LQX/NOPB
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 音頻控制
英文描述： 2 CHANNEL(S), TONE CONTROL CIRCUIT, CQCC28
封裝： LLP-28
文件頁數(shù)： 7/34頁
文件大?。?/td> 1104K
代理商： LM4839LQX/NOPB
Application Information (Continued)
The LM4839 has two operational amplifiers per channel. The
maximum internal power dissipation per channel operating in
the bridge mode is four times that of a single-ended ampli-
fier. From Equation (3), assuming a 5V power supply and a
4
load, the maximum single channel power dissipation is
1.27W or 2.54W for stereo operation.
P
DMAX =4 * (VDD)
2/(2
π2R
L)
Bridge Mode
(3)
The LM4839’s power dissipation is twice that given by Equa-
tion (2) or Equation (3) when operating in the single-ended
mode or bridge mode, respectively. Twice the maximum
power dissipation point given by Equation (3) must not ex-
ceed the power dissipation given by Equation (4):
P
DMAX'=(TJMAX TA)/θJA
(4)
The LM4839’s T
JMAX = 150C. In the LQ package soldered
to a DAP pad that expands to a copper area of 5in
2 on a
PCB, the LM4839’s
θ
JA is 20C/W. In the MTE package
soldered to a DAP pad that expands to a copper area of 2in
2
on a PCB, the LM4839’s
θ
JA is 41C/W. For the LM4839MT
package,
θ
JA = 80C/W. At any given ambient temperature
T
A, use Equation (4) to find the maximum internal power
dissipation supported by the IC packaging. Rearranging
Equation (4) and substituting P
DMAX for PDMAX' results in
Equation (5). This equation gives the maximum ambient
temperature that still allows maximum stereo power dissipa-
tion without violating the LM4839’s maximum junction tem-
perature.
T
A =TJMAX – 2*PDMAX θJA
(5)
For a typical application with a 5V power supply and an 4
load, the maximum ambient temperature that allows maxi-
mum stereo power dissipation without exceeding the maxi-
mum junction temperature is approximately 99C for the LQ
package and 45C for the MTE package.
T
JMAX =PDMAX θJA +TA
(6)
Equation (6) gives the maximum junction temperature
T
JMAX. If the result violates the LM4839’s TJMAX150C, re-
duce the maximum junction temperature by reducing the
power supply voltage or increasing the load resistance. Fur-
ther allowance should be made for increased ambient tem-
peratures.
The above examples assume that a device is a surface
mount part operating around the maximum power dissipation
point. Since internal power dissipation is a function of output
power, higher ambient temperatures are allowed as output
power or duty cycle decreases.
If the result of Equation (2) is greater than that of Equation
(3), then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. If these
measures are insufficient, a heat sink can be added to
reduce
θ
JA. The heat sink can be created using additional
copper area around the package, with connections 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
JA is the sum of θJC, θCS, and θSA.(θJC is the
junction-to-case thermal impedance,
θ
CS is the case-to-sink
thermal impedance, and
θ
SA is the sink-to-ambient thermal
impedance.) Refer to the Typical Performance Character-
istics curves for power dissipation information at lower out-
put 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 10 F in parallel with a 0.1 F filter capacitor to
stabilize 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 1.0 F
tantalum bypass capacitance connected between the
LM4839’s supply pins and ground. Do not substitute a ce-
ramic capacitor for the tantalum. Doing so may cause oscil-
lation. Keep the length of leads and traces that connect
capacitors between the LM4839’s power supply pin and
ground as short as possible. Connecting a 1F capacitor,
C
B, 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 a capacitor, however,
increases turn-on time and can compromise the amplifier’s
click and pop performance. The selection of bypass capaci-
tor values, especially C
B, depends on desired PSRR require-
ments, click and pop performance (as explained in the sec-
tion, Proper Selection of External Components), system
cost, and size constraints.
PROPER SELECTION OF EXTERNAL COMPONENTS
Optimizing the LM4839’s performance requires properly se-
lecting external components. Though the LM4839 operates
well when using external components with wide tolerances,
best performance is achieved by optimizing component val-
ues.
The LM4839 is unity-gain stable, giving a designer maximum
design flexibility. The gain should be set to no more than a
given application requires. This allows the amplifier to
achieve minimum THD+N and maximum signal-to-noise ra-
tio. These parameters are compromised as the closed-loop
gain increases. However, low gain circuits demand input
signals with greater voltage swings to achieve maximum
output power. Fortunately, many signal sources such as
audio CODECs have outputs of 1V
RMS (2.83VP-P). Please
refer to the Audio Power Amplifier Design section for more
information on selecting the proper gain.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires a high
value input coupling capacitor (0.33F in
Figure 1). A high
value capacitor can be expensive and may compromise
space efficiency in portable designs. In many cases, how-
ever, the speakers used in portable systems, whether inter-
nal or external, have little ability to reproduce signals below
150Hz. Applications using speakers with this limited fre-
quency response reap little improvement by using a large
input capacitor.
Besides effecting system cost and size, the input coupling
capacitor has an affect on the LM4835’s click and pop per-
formance. When the supply voltage is first applied, a tran-
sient (pop) is created as the charge on the input capacitor
changes from zero to a quiescent state. The magnitude of
the pop is directly proportional to the input capacitor’s size.
LM4839
www.national.com
15
相關(guān)PDF資料
PDF描述
LM4840LQX/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC28
LM4840LQ/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC28
LM4840MTX/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO28
LM4840MT/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO28
LM4840MHX/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO28
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM4839MT 制造商:Texas Instruments 功能描述:Stereo 1.1W Audio Amplifiers,LM4839MT
LM4839MT/NOPB 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝: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，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR)
LM4839MTBD 功能描述:BOARD EVALUATION LM4839MT RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:1 系列:-
LM4839MTE 制造商:Texas Instruments 功能描述:AMP AUDIO STEREO 2.2W SMD TSSOP28
LM4839MTE/NOPB 功能描述:IC AMP AUDIO PWR 2.2W AB 28TSSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝: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，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR)
發(fā)布緊急采購，3分鐘左右您將得到回復。

采購需求

(若只采購一條型號，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進入我的后臺，查看報價

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進入我的后臺，查看報價

*型號 *數(shù)量 廠商 批號 封裝
添加更多采購

我的聯(lián)系方式

*
*
*