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| 型号： | MAX9741ETN+D |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 4/16页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO PWR 12W STER 56TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 37 |
| 类型： | D 类 |
| 输出类型： | 2 通道（立体声） |
| 在某负载时最大输出功率 x 通道数量： | 12W x 2 @ 8 欧姆 |
| 电源电压： | 10 V ~ 25 V |
| 特点： | 消除爆音，差分输入，静音，短路和热保护，关机 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 56-TQFN-EP（8x8） |
| 封装/外壳： | 56-WFQFN 裸露焊盘 |
| 包装： | 管件 |
MAX9741
12W+12W, Low-EMI, Spread-Spectrum,
Stereo, Class D Amplifier
12
______________________________________________________________________________________
Audio content, both music and voice, has a much lower
RMS value relative to its peak output power. Figure 5
shows a sine wave and an audio signal in the time
domain. Both are measured for RMS value by the oscil-
loscope. Although the audio signal has a slightly higher
peak value than the sine wave, its RMS value is almost
half that of the sine wave. Therefore, while an audio sig-
nal may reach similar peaks as a continuous sine wave,
the actual thermal impact on the Class D amplifier is
highly reduced. If the thermal performance of a system
is being evaluated, it is important to use actual audio
signals instead of sine waves for testing. If sine waves
must be used, the thermal performance will be less
than the system’s actual capability.
PC Board Thermal Considerations
The exposed pad is the primary route of heat away
from the IC. With a bottom-side exposed pad, the PC
board and its copper becomes the primary heatsink for
the Class D amplifier. Solder the exposed pad to a
large copper polygon. Add as much copper as possi-
ble from this polygon to any adjacent pin on the Class
D amplifier as well as to any adjacent components, pro-
vided these connections are at the same potential.
These copper paths must be as wide as possible. Each
of these paths contributes to the overall thermal capa-
bilities of the system.
The copper polygon to which the exposed pad is
attached should have multiple vias to the opposite side
of the PC board, where they connect to another copper
polygon. Make this polygon as large as possible within
the system’s constraints for signal routing.
Additional improvements are possible if all the traces
from the device are made as wide as possible.
Although the IC pins are not the primary thermal path
out of the package, they do provide a small amount.
The total improvement would not exceed approximately
10%, but it could make the difference between accept-
able performance and thermal problems.
With a bottomside exposed pad, the lowest resistance
thermal path is on the bottom of the PC board. The topside
of the IC is not a significant thermal path for the device.
Thermal Calculations
The die temperature of a Class D amplifier can be esti-
mated with some basic calculations. For example, the
die temperature is calculated for the below conditions:
TA = +40°C
POUT = 10W (5W + 5W)
Efficiency (
η) = 78%
θJA = 21°C/W
First, the Class D amplifier’s power dissipation must be
calculated.
Then the power dissipation is used to calculate the die
temperature, TC, as follows:
Load Impedance
The on-resistance of the MOSFET output stage in Class
D amplifiers affects both the efficiency and the peak-
current capability. Reducing the peak current into the
load reduces the I2R losses in the MOSFETs, increas-
ing efficiency. To keep the peak currents lower, choose
the highest impedance speaker which can still deliver
the desired output power within the voltage swing limits
of the Class D amplifier and its supply voltage.
Optimize MAX9741 Efficiency with
Load Impedance and Supply Voltage
To optimize efficiency, load the output stage with 12
to 16
speakers. The MAX9741 exhibits highest effi-
ciency performance when driving higher load imped-
ance (see the Typical Operating Characteristics). If a
12
to 16 load is not available, select a lower supply
voltage when driving 4
to 10 loads.
For best performance, choose a speaker impedance to
complement the required output power and the available
supply voltage. For example, if operating from a 24V sup-
ply and a peak output of 10W per channel is desired, using
12
speakers provides the best audio performance and
power efficiency. The amplifier outputs are short-circuit
protected at approximately 2A. Selecting a higher imped-
ance driver helps prevent exceeding the current limit.
TT
P
C
W
C W
C
CA
DISS
JA
=+
×
= ° +
× °
=
°
θ
40
2 82
21
99 2
./
.
P
W
WW
DISS
OUT
==
=
η
10
78
10
2 82
%
.
20ms/div
Figure 5. RMS Comparison of Sine Wave vs. Audio Signal
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX9741EVKIT | 制造商:Maxim Integrated Products 功能描述:12W+12W FILTERLESS - Rail/Tube 制造商:Maxim Integrated Products 功能描述:12W+12W FILTERLESS SPREAD-SPECTRU - Rail/Tube |
| MAX9742ETX+ | 功能描述:音频放大器 Stereo 16W Class D Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9742ETX+T | 功能描述:音频放大器 Stereo 16W Class D Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9742EVKIT+ | 功能描述:音频放大器 Evaluation Kit for the MAX9742 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9744ETH+ | 功能描述:音频放大器 Stereo 20W Class D Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
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