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ADV7123KSTZ50 参数 Datasheet PDF下载

ADV7123KSTZ50图片预览
型号: ADV7123KSTZ50
PDF下载: 下载PDF文件 查看货源
内容描述: CMOS , 330 MHz的三路10位高速视频DAC [CMOS, 330 MHz Triple 10-Bit High Speed Video DAC]
分类和应用: 转换器数模转换器PC
文件页数/大小: 24 页 / 340 K
品牌: ADI [ ADI ]
 浏览型号ADV7123KSTZ50的Datasheet PDF文件第15页浏览型号ADV7123KSTZ50的Datasheet PDF文件第16页浏览型号ADV7123KSTZ50的Datasheet PDF文件第17页浏览型号ADV7123KSTZ50的Datasheet PDF文件第18页浏览型号ADV7123KSTZ50的Datasheet PDF文件第20页浏览型号ADV7123KSTZ50的Datasheet PDF文件第21页浏览型号ADV7123KSTZ50的Datasheet PDF文件第22页浏览型号ADV7123KSTZ50的Datasheet PDF文件第23页  
ADV7123  
Z
Z
1
2
Figure 23 shows the video waveforms associated with the three  
RGB outputs driving the doubly terminated 75 ꢁ load of Figure 24.  
As well as the gray scale levels, black level to white level, Figure 23  
+V  
7
0.1µF  
S
2
3
Z
= 75  
0
75Ω  
SYNC  
BLANK  
IOR, IOG, IOB  
DACs  
also shows the contributions of  
and  
for the  
AD848  
6
ADV7123. These control inputs add appropriately weighted  
currents to the analog outputs, producing the specific output  
level requirements for video applications. Table 9 details how  
(CABLE)  
Z
= 75Ω  
0.1µF  
4
L
(MONITOR)  
Z
= 75Ω  
(SOURCE  
TERMINATION)  
S
–V  
S
Z
1
GAIN (G) = 1 +  
SYNC  
BLANK  
the  
and  
inputs modify the output levels.  
Z
2
Figure 27. AD848 As an Output Buffer  
GRAY SCALE OPERATION  
The ADV7123 can be used for standalone, gray scale (mono-  
chrome), or composite video applications (that is, only one  
channel used for video information). Any one of the three  
channels, red, green, or blue, can be used to input the digital  
video data. The two unused video data channels should be tied  
to Logic 0. The unused analog outputs should be terminated  
with the same load as that for the used channel; that is, if the  
red channel is used and IOR is terminated with a doubly  
terminated 75 ꢁ load (37.5 ꢁ), IOB and IOG should be  
terminated with 37.5 ꢁ resistors (see Figure 26).  
PCB LAYOUT CONSIDERATIONS  
The ADV7123 is optimally designed for lowest noise perfor-  
mance, both radiated and conducted noise. To complement the  
excellent noise performance of the ADV7123, it is imperative  
that great care be given to the PCB layout. Figure 28 shows a  
recommended connection diagram for the ADV7123.  
The layout should be optimized for lowest noise on the  
ADV7123 power and ground lines. This can be achieved by  
shielding the digital inputs and providing good decoupling.  
Shorten the lead length between groups of VAA and GND pins  
to minimize inductive ringing.  
DOUBLY  
R0  
R9  
IOR  
IOG  
TERMINATED  
VIDEO  
OUTPUT  
7.5LOAD  
It is recommended to use a 4-layer printed circuit board with a  
single ground plane. The ground and power planes should  
separate the signal trace layer and the solder side layer. Noise  
on the analog power plane can be further reduced by using  
multiple decoupling capacitors (see Figure 28). Optimum  
performance is achieved by using 0.1 μF and 0.01 μF ceramic  
capacitors. Individually decouple each VAA pin to ground by  
placing the capacitors as close as possible to the device with the  
capacitor leads as short as possible, thus minimizing lead  
inductance. It is important to note that while the ADV7123  
contains circuitry to reject power supply noise, this rejection  
decreases with frequency. If a high frequency switching power  
supply is used, pay close attention to reducing power supply  
noise. A dc power supply filter (Murata BNX002) provides EMI  
suppression between the switching power supply and the main  
PCB. Alternatively, consideration can be given to using a 3-  
terminal voltage regulator.  
37.5Ω  
37.5Ω  
ADV7123  
G0  
G9  
IOB  
B0  
B9  
GND  
Figure 26. Input and Output Connections for Standalone Gray Scale or  
Composite Video  
VIDEO OUTPUT BUFFERS  
The ADV7123 is specified to drive transmission line loads. The  
analog output configuration to drive such loads is described in  
the Analog Outputs section and illustrated in Figure 27. However,  
in some applications it may be required to drive long transmis-  
sion line cable lengths. Cable lengths greater than 10 meters can  
attenuate and distort high frequency analog output pulses. The  
inclusion of output buffers compensates for some cable distortion.  
Buffers with large full power bandwidths and gains between  
two and four are required. These buffers also need to be able to  
supply sufficient current over the complete output voltage swing.  
Analog Devices produces a range of suitable op amps for such  
applications. These include the AD843, AD844, AD847, and  
AD848 series of monolithic op amps. In very high frequency  
applications (80 MHz), the AD8061 is recommended. More  
information on line driver buffering circuits is given in the  
relevant op amp data sheets.  
DIGITAL SIGNAL INTERCONNECT  
Isolate the digital signal lines to the ADV7123 as much as  
possible from the analog outputs and other analog circuitry.  
Digital signal lines should not overlay the analog power plane.  
Due to the high clock rates used, long clock lines to the  
ADV7123 should be avoided to minimize noise pickup.  
Connect any active pull-up termination resistors for the digital  
inputs to the regular PCB power plane (VCC) and not the analog  
power plane.  
Use of buffer amplifiers also allows implementation of other  
video standards besides RS-343A and RS-170. Altering the gain  
components of the buffer circuit results in any desired video level.  
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