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PAM8803 参数 Datasheet PDF下载

PAM8803图片预览
型号: PAM8803
PDF下载: 下载PDF文件 查看货源
内容描述: 3W立体声无滤波器D类音频放大器,具有数字音量控制 [3W Filterless Stereo Class-D Audio Amplifier with Digital Volume Control]
分类和应用: 音频放大器
文件页数/大小: 13 页 / 304 K
品牌: PAM [ POWER ANALOG MICOELECTRONICS ]
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PAM8803  
3W Filterless Stereo Class-D Audio Amplifier  
with Digital Volume Control  
Application Information  
Maximum Gain  
There are 64 discrete gain settings ranging from  
+24dB maximum to -75dB minimum. Upon device  
As shown in block diagram(page 2),the PAM8803  
has two internal amplifiers stage. The first  
stage's gain is externally configurable, while the  
second stage's is internally fixed in a fixed-gain,  
inverting configuration. The closed-loop gain of  
the first stage is set by selecting the ratio of Rf to  
Ri while the second stage's gain is fixed at 2x.  
Consequently, the differential gain for the IC is  
power on or applied a logic low to the RST pin,  
the amplifier's gain is set to a default value of  
2.6dB. However, when coming out of mute mode,  
the PAM8803 will revert back to its previous gain  
setting. Volume levels for each step vary and are  
specified in Gain Setting table on page 7.  
If both the UP and DN pins are held high, no  
volume change will occur. Trigger points for the  
UP and DN pins are at 70% of VDD minimum for a  
logic high, and 20% of VDD maximum for a logic  
low. It is recommended, however, to toggle UP  
and DN between VD D and GND for best  
performance.  
AVD=20*log [2*(Rf/Ri)]  
The PAM8803 sets maximum Rf=218kΩ and  
minimum Ri=27kΩ, thus the maximum closed-  
gain is 24dB.  
Digital Volume Control (DVC)  
UP/DN  
The PAM8803 features a digital volume control  
which consists of the UP, DN and RST pins. An  
internal clock is used where the clock frequency  
value is determined from the following formula:  
VOLUME  
LEVEL  
2 cycles  
9.5 cycles  
3.5 cycles  
2 cycles  
Figure 1.Timming Diagram  
Mute Operation  
fCLK = fOSC / 213  
The MUTE pin is an input for controlling the  
output state of the PAM8803. A logic low on this  
pin disables the outputs, and a logic high on this  
pin enables the outputs. This pin may be used as  
a quick disable or enable of the outputs without a  
volume fade. Quiescent current is listed in the  
electrical characteristic table. The MUTE pin can  
be left floating due to the pull-up internal.  
The oscillator frequency fOSC value is 200kHz  
typical,with 20% tolerance.The DVC’s clock  
frequency is 33Hz (cycle time 30ms) typical.  
Volume changes are then effected by toggling  
either the UP or DN pins with a logic low. After a  
period of 3.5 clocks pulses with either the UP or  
DN pins held low, the volume will change to the  
next specified step, either UP or DN, and  
followed by a short delay. This delay decreases  
the longer the line is held low, eventually  
reaching a delay of zero. The delay allows the  
user to pull the UP or DN terminal low once for  
one volume change, or hold down to ramp  
several volume changes. The delay is optimally  
configured for push button volume control.  
Shutdown operation  
In order to reduce power consumption while not  
in use, the PAM8803 contains shutdown circuitry  
that is used to turn off the amplifier's bias  
circuitry. This shutdown feature turns the  
amplifier off when logic low is placed on the  
SHDN pin. By switching the SHDN pin connected  
to GND, the PAM8803 supply current draw will be  
minimized in idle mode. The SHDN pin cannot be  
left floating due to the pull-down internal.  
If either the UP or DN pin remains low after the  
first volume transition the volume will change  
again, but this time after 9.5 clock pulses. The  
followed transition occurs at 2 clock pulses for  
each volume transition. This is intended to  
provide the user with a volume control that  
pauses briefly after initial application, and then  
slowly increases the rate of volume change as it  
is continuously applied. This cycle is shown in  
the timing diagram shown in figure 1.  
Power Analog Microelectronics,Inc  
www.poweranalog.com  
12/2009 Rev 1.4  
9