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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 ]
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ADV7123  
CIRCUIT DESCRIPTION AND OPERATION  
The ADV7123 contains three 10-bit DACs, with three input  
channels, each containing a 10-bit register. Also integrated  
on board the part is a reference amplifier. The CRT control  
Table 9 details the resultant effect on the analog outputs of  
BLANK SYNC  
and  
.
All these digital inputs are specified to accept TTL logic levels.  
BLANK  
functions,  
ADV7123.  
SYNC  
and  
, are integrated on board the  
CLOCK INPUT  
The CLOCK input of the ADV7123 is typically the pixel clock  
rate of the system. It is also known as the dot rate. The dot rate,  
and thus the required CLOCK frequency, is determined by the  
on-screen resolution, according to the following equation:  
DIGITAL INPUTS  
There are 30 bits of pixel data (color information), R0 to R9, G0  
to G9, and B0 to B9, latched into the device on the rising edge  
of each clock cycle. This data is presented to the three 10-bit  
DACs and then converted to three analog (RGB) output  
waveforms (see Figure 22).  
Dot Rate = (Horiz Res) × (Vert Res) × (Refresh Rate)/  
(Retrace Factor)  
where:  
CLOCK  
Horiz Res is the number of pixels per line.  
Vert Res is the number of lines per frame.  
DIGITAL INPUTS  
(R9 TO R0, G9 TO G0,  
DATA  
Refresh Rate is the horizontal scan rate. This is the rate at which  
the screen must be refreshed, typically 60 Hz for a noninterlaced  
system, or 30 Hz for an interlaced system.  
Retrace Factor is the total blank time factor. This takes into  
account that the display is blanked for a certain fraction of the  
total duration of each frame (for example, 0.8).  
B9 TO B0,  
SYNC, BLANK)  
ANALOG OUTPUTS  
(IOR, IOR, IOG, IOG,  
IOB, IOB)  
Figure 22. Video Data Input/Output  
The ADV7123 has two additional control signals that are latched  
Therefore, for a graphics system with a 1024 × 1024 resolution,  
a noninterlaced 60 Hz refresh rate, and a retrace factor of 0.8,  
BLANK  
to the analog video outputs in a similar fashion.  
and  
are each latched on the rising edge of CLOCK to maintain  
synchronization with the pixel data stream.  
BLANK SYNC  
SYNC  
Dot Rate = 1024 × 1024 × 60/0.8 = 78.6 MHz  
The required CLOCK frequency is thus 78.6 MHz.  
The  
and  
functions allow for the encoding of  
All video data and control inputs are latched into the ADV7123  
on the rising edge of CLOCK, as described in the Digital Inputs  
section. It is recommended that the CLOCK input to the  
ADV7123 be driven by a TTL buffer (for example, 74F244).  
these video synchronization signals onto the RGB video output.  
This is done by adding appropriately weighted current sources  
to the analog outputs, as determined by the logic levels on the  
BLANK  
SYNC  
and  
output, RGB video waveform of the ADV7123. The influence of  
SYNC BLANK  
digital inputs. Figure 23 shows the analog  
and  
on the analog video waveform is illustrated.  
RED AND BLUE  
GREEN  
mA  
V
mA  
V
18.67  
0.7  
26.0  
0.975  
WHITE LEVEL  
BLANK LEVEL  
SYNC LEVEL  
0
0
7.2  
0.271  
0
0
NOTES  
1. OUTPUTS CONNECTED TO A DOUBLY TERMINATED 75LOAD.  
2. V = 1.235V, R = 530.  
REF SET  
3. RS-343 LEVELS AND TOLERANCES ASSUMED ON ALL LEVELS.  
Figure 23. Typical RGB Video Output Waveform  
Rev. D | Page 17 of 24