参数资料
| 型号： | MAX9756EVKIT |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 6/13页 |
| 文件大小： | 0K |
| 描述： | EVAL KIT FOR MAX9756 |
| 标准包装： | 1 |
| 类型： | 放大器：AB 类音频放大器 |
| 适用于相关产品： | MAX9756 |
| 所含物品： | 完全组装的评估板 |
MAX9756 Evaluation Kit
Step 1. Define the Output
Power Threshold
The output power threshold is defined by the desired
power rating (P OUT ) and the nominal impedance (R L )
of the application ’ s speakers. To set the threshold at
which the speaker output is clamped, an external resis-
tor must be connected from PREF to ground. The sug-
gested external resistor range is from 100k ? to 200k ?
(for best results use a 1% resistor). Leave PREF uncon-
nected to disable the ALC function.
Use the following equation to select the value of P PREF
for the desired maximum continuous output power
V PEAK
V RMS
V RMS = V PEAK
level, P OUT , assuming a sine-wave input signal:
? P OUT ? ? R L ?
P PREF = 180 k ? ? ? × ? ?
? 1 . 166 ? ? 8 ?
Note the MAX9756 ALC circuitry is based on a peak
signal detection algorithm. If a heavily clipped signal is
passed to the speaker, the resulting increased continu-
ous output power can potentially damage the speaker.
Take two waveforms with equal amplitude, for example
(Figure 2). The RMS voltage of the square wave is
1.414 times the peak voltage of the sine wave. In terms
of power, the total power of the square wave is double
the power of the sine wave.
The MAX9756 EV kit provides resistor R4 in series with
potentiometer R5 to adjust the output power threshold of
the MAX9756. The series resistance of R4 and R5 is
Figure 2. RMS Voltage of a Sine Wave vs. RMS Voltage of a
Square Wave
6dB
COMPRESSION
V OUT
referred to as R PREF . Resistor R3 is shipped uninstalled,
but is made available for occasions where a single resis-
tor is desired for evaluation. If resistor R3 is installed,
uninstall resistor R4.
Step 2. Define the Gain Setting
Accurately defining the gain setting of the MAX9756
amplifier is key to obtaining optimum ALC performance.
V IN [dB]
ALC TRANSFER FUNCTION
LINEAR TRANSFER FUNCTION
Figure 3. Amplifier Gain Selection
FS INPUT
[ ]
The overall gain structure must be set to ensure the
ALC circuitry is fully limiting with full-scale signals. This
gain structure will ensure the amplifier quickly responds
to an overdriven output condition. The design of the
MAX9756 limits ALC gain reduction to a maximum of
6dB, after which the output voltage will increase above
the defined threshold.
Select the gain (A V ) of the amplifier so that a full-scale
input signal (V INFS ) produces a fully compressed out-
put at the output threshold defined in Step 1.
A V = 2 ( P OUT × R L )
V INFS [ V / V ]
where V INFS is an RMS value.
If the ideal value is not available from the fixed-gain
options of the MAX9756, choose the closest setting to
the above.
Once a gain setting is selected, test the ALC threshold
with a 0dBFS, 1kHz input signal. Monitor the CT pin of
the MAX9756 to ensure the ALC circuitry is active. The
voltage at CT should be more than 3.5V under these
conditions. Increase the amplifier gain setting if the volt-
age at CT does not go above 3.5V with a 0dBFS input.
Jumpers JU2, JU3, and JU4 of the MAX9756 EV kit pro-
vide an option to set the maximum gain of the speakers
and headphone amplifiers on the EV kit. See Table 2 for
shunt positions.
6
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| MAX9757ETJ+ | 功能描述:音频放大器 Integrated Circuits (ICs) 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 |
| MAX9757ETJ+T | 功能描述:音频放大器 Integrated Circuits (ICs) 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 |
| MAX9758ETJ+ | 功能描述:音频放大器 Integrated Circuits (ICs) 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 |
| MAX9758ETJ+T | 功能描述:音频放大器 Integrated Circuits (ICs) 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 |
| MAX9759ETE+ | 功能描述:音频放大器 3.2W Low-EMI 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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