- 您现在的位置：买卖IC网 > PDF目录30754 > LM4871N/NOPB (NATIONAL SEMICONDUCTOR CORP) 1.5 W, 1 CHANNEL, AUDIO AMPLIFIER, PDIP8 PDF资料下载
参数资料
| 型号： | LM4871N/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 1.5 W, 1 CHANNEL, AUDIO AMPLIFIER, PDIP8 |
| 封装： | DIP-8 |
| 文件页数： | 16/16页 |
| 文件大小： | 472K |
| 代理商： | LM4871N/NOPB |
Application Information (Continued)
LD (LLP) package is available from National Semiconduc-
tor’s Package Engineering Group under application note
AN1187.
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 3
AND 4 LOADS
Power dissipated by a load is a function of the voltage swing
across the load and the load’s impedance. As load imped-
ance decreases, load dissipation becomes increasingly de-
pendant on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connec-
tions. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1
trace resistance reduces
the output power dissipated by a 4
load from 2.0W to
1.95W. This problem of decreased load dissipation is exac-
erbated as load impedance decreases. Therefore, to main-
tain the highest load dissipation and widest output voltage
swing, PCB traces that connect the output pins to a load
must be as wide as possible.
Poor power supply regulation adversely affects maximum
output power. A poorly regulated supply’s output voltage
decreases with increasing load current. Reduced supply
voltage causes decreased headroom, output signal clipping,
and reduced output power. Even with tightly regulated sup-
plies, trace resistance creates the same effects as poor
supply regulation. Therefore, making the power supply
traces as wide as possible helps maintain full output voltage
swing.
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4871 has two operational
amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier’s gain is externally config-
urable; the second amplifier is internally fixed in a unity-gain,
inverting configuration. The closed-loop gain of the first am-
plifier is set by selecting the ratio of R
f to Ri while the second
amplifier’s gain is fixed by the two internal 40k
resistors.
Figure 1 shows that the output of amplifier one serves as the
input to amplifier two, which results in both amplifiers pro-
ducing signals identical in magnitude, but 180 out of phase.
Consequently, the differential gain for the IC is
A
VD= 2 *(Rf/Ri)
By driving the load differentially through outputs Vo1 and
Vo2, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is
different from the classical single-ended amplifier configura-
tion where one side of its load is connected to ground.
A bridge amplifier design has a few distinct advantages over
the single-ended configuration, as it provides differential
drive to the load, thus doubling output swing for a specified
supply voltage. Four times the output power is possible as
compared to a single-ended amplifier under the same con-
ditions. This increase in attainable output power assumes
that the amplifier is not current limited or clipped. In order to
choose an amplifier’s closed-loop gain without causing ex-
cessive clipping, please refer to the Audio Power Amplifier
Design section.
Another advantage of the differential bridge output is no net
DC voltage across load. This results from biasing V
O1 and
V
O2 at the same DC voltage, in this case VDD/2 . This
eliminates the coupling capacitor that single supply, single-
ended amplifiers require. Eliminating an output coupling ca-
pacitor in a single-ended configuration forces a single supply
amplifier’s half-supply bias voltage across the load. The
current flow created by the half-supply bias voltage in-
creases internal IC power dissipation and my permanently
damage loads such as speakers.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power
delivered to the load by a bridge amplifier is an increase in
internal power dissipation. Equation 1 states the maximum
power dissipation point for a bridge amplifier operating at a
given supply voltage and driving a specified output load.
P
DMAX = 4*(VDD)
2/(2
π2R
L)
(1)
Since the LM4871 has two operational amplifiers in one
package, the maximum internal power dissipation is 4 times
that of a single-ended ampifier. Even with this substantial
increase in power dissipation, the LM4871 does not require
heatsinking under most operating conditions and output
loading. From Equation 1, assuming a 5V power supply and
an 8
load, the maximum power dissipation point is
625 mW. The maximum power dissipation point obtained
from Equation 1 must not be greater than the power dissi-
pation that results from Equation 2:
P
DMAX =(TJMAX–TA)/
θ
JA
(2)
For the SO package,
θ
JA = 140C/W, for the DIP package,
θ
JA = 107C/W, and for the MSOP package,
θ
JA = 210C/W
assuming free air operation. For the LD package soldered to
a DAP pad that expands to a copper area of 1.0in
2 on a
PCB, the LM4871’s
θ
JA is 56C/W. TJMAX = 150C for the
LM4871. The
θ
JA can be decreased by using some form of
heat sinking. The resultant
θ
JA will be the summation of the
θ
JC,
θ
CS, and
θ
SA.
θ
JC is the junction to case of the package
(or to the exposed DAP, as is the case with the LD package),
θ
CS is the case to heat sink thermal resistance and
θ
SA is the
heat sink to ambient thermal resistance. By adding addi-
tional copper area around the LM4871, the
θ
JA can be
reduced from its free air value for the SO and MSOP pack-
ages. Increasing the copper area around the LD package
from 1.0in
2 to 2.0in2 area results in a
θ
JA decrease to
46C/W. Depending on the ambient temperature, T
A, and the
θ
JA, Equation 2 can be used to find the maximum internal
power dissipation supported by the IC packaging. If the
result of Equation 1 is greater than that of Equation 2, then
either the supply voltage must be decreased, the load im-
pedance increased, the
θ
JA decreased, or the ambient tem-
perature reduced. For the typical application of a 5V power
supply, with an 8
load, and no additional heatsinking, the
maximum ambient temperature possible without violating the
maximum junction temperature is approximately 61C pro-
vided that device operation is around the maximum power
dissipation point and assuming surface mount packaging.
For the LD package in a typical application of a 5V power
supply, with a 4
load, and 1.0in2 copper area soldered to
the exposed DAP pad, the maximum ambient temperature is
approximately 77C providing device operation is around the
maximum power dissipation point. Internal power dissipation
is a function of output power. If typical operation is not
around the maximum power dissipation point, the ambient
temperature can be increased. Refer to the Typical Perfor-
mance Characteristics curves for power dissipation infor-
mation for different output powers and output loading.
LM4871
www.national.com
9
相关PDF资料 |
PDF描述 |
|---|---|
| LM4872IBPX/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA8 |
| LM4872IBP/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA8 |
| LM4873MDC | 1.1 W, 2 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM4873MWC | 1.1 W, 2 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM4874MH/NOPB | 2.6 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO20 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4872 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1 Watt Audio Power Amplifier in micro SMD package |
| LM4872IBP | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD RoHS:否 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4872IBPX | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4872ITP | 制造商:Texas Instruments 功能描述:AMP AUDIO 1W BOOMER SMD 4872 |
| LM4872ITP/NOPB | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
发布紧急采购，3分钟左右您将得到回复。