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PAM8303DAZN 参数 Datasheet PDF下载

PAM8303DAZN图片预览
型号: PAM8303DAZN
PDF下载: 下载PDF文件 查看货源
内容描述: 超低EMI ,无需滤波器3W单声道D类音频功率放大器 [Ultra Low EMI, 3W Filterless Mono Class-D Audio Power Amplifier]
分类和应用: 放大器功率放大器
文件页数/大小: 17 页 / 273 K
品牌: PAM [ POWER ANALOG MICOELECTRONICS ]
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PAM8303D  
Ultra Low EMI, 3W Filterless  
Mono Class-D Audio Power Amplifier  
Application Information  
Input Resistance (Ri)  
For this reason, a low-leakage tantalum or  
ceramic capacitor is the best choice. When  
polarized capacitors are used, the positive side  
of the capacitor should face the amplifier input in  
most applications as the DC level is held at VDD/2,  
which is likely higher than the source DC level.  
Please note that it is important to confirm the  
capacitor polarity in the application.  
The input resistors (Ri) set the gain of the  
amplifier according to Equation 1.  
2´150kW V  
æ
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Gain =  
ç
÷
ø
Ri  
V
è
Resistor matching is very important in fully  
differential amplifiers. The balance of the output  
on the reference voltage depends on matched  
ratios of the resistors. CMRR, PSRR, and  
cancellation of the second harmonic distortion  
diminish if resistor mismatch occurs. Therefore,  
it is recommended to use 1% tolerance resistors  
or better to keep the performance optimized.  
Matching is more important than overall  
tolerance. Resistor arrays with 1% matching can  
be used with a tolerance greater than 1%.  
Decoupling Capacitor (CS )  
The PAM8303D is a high-performance CMOS  
audio amplifier that requires adequate power  
supply decoupling to ensure the output total  
harmonic distortion (THD) as low as possible.  
Power supply decoupling also prevents the  
oscillations causing by long lead length between  
the amplifier and the speaker.  
Place the input resistors very close to the  
PAM8303D to limit noise injection on the high-  
impedance nodes.  
The optimum decoupling is achieved by using  
two different types of capacitors that target on  
different types of noise on the power supply  
leads. For higher frequency transients, spikes, or  
digital hash on the line, a good low equivalent-  
series-resistance (ESR) ceramic capacitor,  
typically 1μF, is placed as close as possible to  
the device each VDD and PVDD pin for the best  
operation. For filtering lower frequency noise  
signals, a large ceramic capacitor of 10μF or  
greater placed near the audio power amplifier is  
recommended.  
For optimal performance the gain should be set  
to 2X(Ri=150k) or lower. Lower gain allows the  
PAM8303D to operate at its best, and keeps a  
high voltage at the input making the inputs less  
susceptible to noise. In addition to these  
features, higher value of Ri minimizes pop noise.  
Input Capacitors (Ci )  
In the typical application, an input capacitor, Ci,  
is required to allow the amplifier to bias the input  
signal to the proper DC level for optimum  
operation. In this case, Ci and the minimum input  
impedance Ri form is a high-pass filter with the  
corner frequency determined in the follow  
How to Reduce EMI  
Most applications require a ferrite bead filter for  
EMI elimination shown at Figure 1. The ferrite  
filter reduces EMI around 1MHz and higher.  
When selecting a ferrite bead, choose one with  
high impedance at high frequencies, but low  
impedance at low frequencies.  
equation:  
1
fC =  
2pRiCi  
(
)
Ferrite Bead  
OUT+  
It is important to consider the value of Ci as it  
directly affects the low frequency performance of  
the circuit. For example, when Ri is 150kΩ and  
the specification calls for a flat bass response  
are down to 150Hz. Equation is reconfigured as  
200pF  
Ferrite Bead  
OUT-  
200pF  
followed:  
1
Ci =  
2pR  
ifc  
(
)
Figure 1: Ferrite Bead Filter to Reduce EMI  
When input resistance variation is considered,  
the Ci is 7nF, so one would likely choose a value  
of 10nF. A further consideration for this capacitor  
is the leakage path from the input source through  
the input network (Ci, Ri + Rf) to the load. This  
leakage current creates a DC offset voltage at  
the input to the amplifier that reduces useful  
headroom, especially in high gain applications.  
Shutdown operation  
In order to reduce power consumption while not  
in use, the PAM8303D contains shutdown  
circuitry that is used to turn off the amplifier’s  
bias circuitry. This shutdown feature turns the  
Power Analog Microelectronics,Inc  
09/2008 Rev 1.4  
www.poweranalog.com  
12