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參數(shù)資料
| 型號： | MAX4455 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Triple Differential Transceivers 20-SOIC -40 to 85 |
| 中文描述： | 任意圖形隨屏顯示視頻發(fā)生器 |
| 文件頁數(shù)： | 18/30頁 |
| 文件大?。?/td> | 663K |
| 代理商： | MAX4455 |
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M
Arbitrary Graphics On-Screen Display
Video Generator
18
______________________________________________________________________________________
techniques can be used in conjunction. A thicker line
exhibits much less of the flicker effect. Once the line is
from five to six lines thick, the additional improvement
from thicker lines is negligible.
Anti-aliasing is a fairly well-known technique that involves
decreasing the severity of the transition of the graphic or
font structure. Here, it involves bracketing a horizontal line
with two or more other lines that have a relative bright-
ness that is between the brightness level of the line and
the background. This is illustrated in Figure 9.
The proper application of this technique softens the
look of the line, which can be undesirable in some
cases. In general, it makes the display easier to read.
Finite Switch Time Effects
The MAX4455 generates the OSDFILL_ and OSDKEY_
signals time coincident with each other within a few
nanoseconds. Since the OSDKEY_ signal controls
when the external fast mux switch switches from normal
camera video to the OSDFILL signal, any finite delay in
the response time of this fast mux switch has an effect
on the resulting OSD insertion (Figure 10).
Due to the finite switching time of the fast mux switch,
both the leading and trailing portions of the OSDFILL_
are inserted slightly later in time. The leading edge
does not create a visible artifact on the screen since it
only shifts the image to the right an amount equal to the
switch delay. The trailing edge of the OSDFILL_ can
result in a visible artifact because the OSDFILL_ signal
has already returned to 0 IRE before the fast mux
switch can transition back to the camera video signal.
This effect is shown in Figure 11.
In a typical NTSC system with a bandwidth of 4.2MHz,
the narrowest resolved image is about 120ns wide. If the
delay of the fast mux switch is less than half of this, 60ns
or less, no visible artifact should be seen on the display.
The displayed information can be designed to dramati-
cally minimize the adverse effect of the finite switch time,
if desired. For example, virtually all fonts and graphics
that are overlayed on normal video need to be outlined
for good readability. A very common technique is to use
white structures with a black outline border. To compen-
sate for the above finite switch time effect, construct the
graphic or font with a thinner trailing edge. When dis-
played, it looks symmetrical with the trailing edge appear-
ing normal. Figure 12 illustrates this technique.
Memory Sharing
Memory sharing is a feature that reduces the host
processor burden for tasks such as time-stamp update.
The MAX4455 supports user-specified starting and
ending lines to be shared by any number of channels.
In Figure 13, the time stamp is written only to channel 0
on line start through line end. Graphics data stored in
lines outside of start and end remain unique for each of
the eight video channels (Figure 13).
In Figure 13, channel 0
’
s start line number through end
line number are duplicated onto channel 2 and channel
4
’
s display. The source of shared data is defined in the
SHRSHC register (see the
MAX4455 Registed Descrip-
tion
section). For example, channel 15 can be pro-
grammed to display channel 7
’
s graphics beginning at
channel 7 start line #n through end line #m, etc.
Sharing is restricted to even channels with even chan-
nels and odd channels with odd channels. For exam-
ple, channels 1, 3, 5, 7 can share lines and channels 0,
2, 4, 6 can share lines in any combination.
Power Supplies and Bypassing
The MAX4455 operates from a single 2.7V to 5.5V analog
supply and a 3V to 3.6V digital supply. Additional logic
supplies for host μP interface (V
H1
) and the OSDKEY_
interface (V
K1
) allow the MAX4455 to interface with other
logic supplies from 2.7V to 5.5V. Bypass each supply pin
with a 0.1μF capacitor to ground.
Layout Concerns
For best performance, make the OSDFILL_ and OSD-
KEY_ output traces as short as possible, and place the
75
termination resistor close to the crosspoint switch
OSDFILL_ input with the resistor terminated to the solid
analog ground plane. The SDRAM interface is the high-
est speed connection and therefore requires careful
layout. Place the SDRAM close to the MAX4455 to mini-
mize trace lengths. The MAX4455 pinout is optimized
for memory bus trace routing to the SDRAM without
crossing traces. Refer to the MAX4455 EV kit for a
proven PC board layout.
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| MAX4455ECQ | Triple Differential Transceivers 20-SOIC -40 to 85 |
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| MAX4504EPA | Low-Voltage, Dual-Supply, SPST, CMOS Analog Switches |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX4455ECQ | 功能描述:視頻開關(guān) IC RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| MAX4455ECQ+D | 功能描述:視頻開關(guān) IC RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| MAX4455ECQ+TD | 功能描述:視頻開關(guān) IC Integrated Circuits (ICs) RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| MAX4455ECQ-T | 功能描述:視頻開關(guān) IC RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| MAX4455EVKIT | 制造商:Maxim Integrated Products 功能描述:ARBITRARY GRAPHICS ON-SCREEN DISPLAY VIDEO GE - Bulk |
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