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CX25870 参数 Datasheet PDF下载

CX25870图片预览
型号: CX25870
PDF下载: 下载PDF文件 查看货源
内容描述: 视频编码器与自适应闪烁过滤和HDTV输出 [Video Encoder with Adaptive Flicker Filtering and HDTV Output]
分类和应用: 电视编码器
文件页数/大小: 291 页 / 3791 K
品牌: CONEXANT [ CONEXANT SYSTEMS, INC ]
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CX25870/871  
3.0 PC Board Considerations  
Flicker-Free Video Encoder with Ultrascale Technology  
3.4 Decoupling  
3.4 Decoupling  
3.4.1 Device Decoupling  
For optimum performance, all capacitors should be located as close as possible to  
the device, and the shortest possible leads (consistent with reliable operation)  
should be used to reduce the lead inductance. Chip capacitors are recommended  
for minimum lead inductance. Radial lead ceramic capacitors can be substituted  
for chip capacitors and are better than axial lead capacitors for self-resonance.  
Values are chosen to have self-resonance above the pixel clock.  
3.4.2 Power Supply Decoupling  
The best power supply performance is obtained with a 0.1 µF ceramic capacitor  
decoupling each group of VAA pins and each group of VDD pins to GND. The  
capacitors should be placed as close as possible to the device VAA/VDD pins and  
GND pins and connected with short, wide traces.  
The 47 µF capacitor shown in Figure 3-2 is for low-frequency power supply  
ripple; the 0.1 µF capacitors are for high-frequency power supply noise rejection.  
Inclusion of a 0.01 µF and a 1.0 µF capacitor between the group of VAA/VDD  
pins and GND/VSS pins will improve power supply decoupling at intermediate  
frequencies as well.  
When a linear regulator is used, the proper power-up sequence must be  
verified to prevent latchup. A linear regulator is recommended to filter the analog  
power supply if the power supply noise is greater than or equal to 200 mV. This is  
especially important when a switching power supply is used, or low voltage  
interface is implemented, and the switching frequency is close to the raster scan  
frequency. About 5 percent of the power supply hum and ripple noise less than  
1 MHz will couple onto the analog outputs.  
3.4.3 COMP Decoupling  
The COMP pin must be decoupled to the closest VAA pin, typically with a 0.1 µF  
ceramic capacitor. Low-frequency supply noise will require a larger value. The  
COMP capacitor must be as close as possible to the COMP and VAA pins. A  
surface-mount ceramic chip capacitor is preferred for minimal lead inductance.  
Lead inductance degrades the noise rejection of the circuit. Short, wide traces will  
also reduce lead inductance.  
3.4.4 VREF Decoupling  
A 1.0 µF ceramic capacitor should be used to decouple this input to GND.  
3.4.5 VBIAS Decoupling  
A 0.1 µF ceramic capacitor should be used to decouple this output to GND.  
100381B  
Conexant  
3-9