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BT861KRF 参数 Datasheet PDF下载

BT861KRF图片预览
型号: BT861KRF
PDF下载: 下载PDF文件 查看货源
内容描述: 多端口的YCrCb到NTSC / PAL / SECAM数字视频编码器 [Multiport YCrCb to NTSC / PAL / SECAM Digital Video Encoder]
分类和应用: 商用集成电路编码器
文件页数/大小: 111 页 / 1232 K
品牌: CONEXANT [ CONEXANT SYSTEMS, INC ]
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Bt860/861  
4.0 Applications  
Multiport YCrCb to NTSC/PAL /SECAM  
4.1 PC Board Considerations  
4.1.8 Digital Signal Interconnect  
The digital inputs to the Bt860/861 should be isolated from the analog outputs  
and other analog circuitry as much as possible and should not overlay the analog  
power plane.  
Most noise on the analog outputs is caused by excessive edge rates (less than  
3 ns), overshoot, undershoot, and ringing on the digital inputs coupling into the  
analog signals. Ringing can be reduced by damping the line with a series resistor  
(30–300 Ω).  
Because feed-through noise is proportional to the digital edge rates,  
lower-speed logic (3–5 ns edge rates) should be used whenever possible. Route  
the digital signals at 90-degree angles to any analog signals.  
4.1.9 Analog Signal Interconnect  
Locate the Bt860/861 as close as possible to the output connectors to minimize  
noise pickup and reflections caused by impedance mismatch. The video output  
signals should overlay the ground plane.  
The analog outputs are susceptible to crosstalk from digital lines; digital traces  
must not be routed under or adjacent to the analog output traces.  
For maximum performance, the analog video output impedance, cable  
impedance, and load impedance should be identical. The load resistor connection  
between the video outputs and AGND should be as close as possible to the  
Bt860/861 to minimize reflections. Turn off all unused analog outputs by setting  
the applicable EN_DAC_x register bit to 0.  
4.1.10 ESD and Latchup Considerations  
Correct ESD-sensitive handling procedures are required to prevent device  
damage, which can produce symptoms ranging from catastrophic failure to erratic  
device behavior with leaky inputs.  
All logic inputs should be held low until power to the device has settled to the  
specified tolerance. DAC power decoupling networks with large time constants  
should be avoided; they could delay VAA and VDD power to the device. Ferrite  
beads must be used only for analog power VAA decoupling. Inductors cause a  
time constant delay that induces latchup, and should not be substituted for ferrite  
beads.  
Latchup can be prevented by ensuring that all power pins are at the same  
potential, all GND pins are at the same potential, and that the VAA and VDD  
supply voltages are applied before the signal pin voltages. The correct power-up  
sequence ensures that any signal pin voltage will never exceed the power supply  
voltage.  
D860DSA  
Conexant  
4-5  
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