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參數(shù)資料
| 型號(hào)： | ADV7128KR30 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | DAC |
| 英文描述： | CMOS 80 MHz, 10-Bit Video DAC |
| 中文描述： | PARALLEL, WORD INPUT LOADING, 10-BIT DAC, PDSO28 |
| 封裝： | SOIC-28 |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大小： | 135K |
| 代理商： | ADV7128KR30 |
ADV7128
REV. 0
–6–
Reference Input
An external 1.23 V voltage reference is required to drive the
ADV7128. T he AD589 from Analog Devices is an ideal choice
of reference. It is a two-terminal, low cost, temperature com-
pensated bandgap voltage reference which provides a fixed
1.23 V output voltage for input currents between 50
μ
A and
5 mA. Figure 4 shows a typical reference circuit connection dia-
gram. T he voltage reference gets its current drive from the
ADV7128’s V
AA
through an on-board 1 k
resistor to the V
REF
pin. A 0.1
μ
F ceramic capacitor is required between the COMP
pin and V
AA
. T his is necessary so as to provide compensation for
the internal reference amplifier.
A resistance R
SET
connected between R
SET
and GND deter-
mines the amplitude of the output video level according to the
following equation:
I
OUT
(mA) =
7,969
×
V
REF
(V)/R
SET
(
)
(1)
Using a variable value of R
SET
, as shown in Figure 4, allows for
accurate adjustment of the analog output video levels. Use of a
fixed 560
R
SET
resistor yields the analog output levels as
quoted in the specification page. T hese values typically corre-
spond to the RS-343A video waveform values as shown in
Figure 3.
TO DAC
V
AA
V
REF
GND
1k
RSET
SET
R
560
500
100
*ADDITIONAL CIRCUITRY, INCLUDING DECOUPLING COMPONENTS,
EXCLUDED FOR CLARITY
ANALOG POWER PLANE
COMP
0.01
μ
F
5V
+
5mA
I
REF
~
AD589
(1.235V
VOLTAGE
REFERENCE)
ADV7128
Figure 4. Reference Circuit
D/A Converter
T he ADV7128 contains a 10-bit D/A converter. T he DAC is
designed using an advanced, high speed, segmented architec-
ture. T he bit currents corresponding to each digital input are
routed to either the analog output (bit = “1”) or GND (bit =
“0”) by a sophisticated decoding scheme. T he use of identical
current sources in a monolithic design guarantees monotonicity
and low glitch. T he on-board operational amplifier stabilizes the
full-scale output current against temperature and power supply
variations.
Analog Output
T he analog output of the ADV7128 is a high impedance current
source. T he current output is capable of directly driving a
37.5
load, such as a doubly terminated 75
coaxial cable.
Figure 5a shows the required configuration for the output con-
nected into a doubly terminated 75
load. T his arrangement
will develop RS-343A video output voltage levels across a 75
monitor.
DAC
I
OUT
Z
O
= 75
(CABLE)
Z
S
= 75
(SOURCE
TERMINATION)
Z
L
= 75
(MONITOR)
Figure 5a. Analog Output Termination for RS-343A
A suggested method of driving RS-170 video levels into a 75
monitor is shown in Figure 5b. T he output current level of the
DAC remains unchanged, but the source termination resistance,
Z
S
, on the DAC is increased from 75
to 150
.
DAC
I
OUT
Z
O
= 75
(CABLE)
Z
S
= 150
(SOURCE
TERMINATION)
Z
= 75
(MONITOR)
Figure 5b. Analog Output Termination for RS-170
More detailed information regarding load terminations for vari-
ous output configurations, including RS-343A and RS-170, is
available in an Application Note entitled “Video Formats & Re-
quired Load T erminations” available from Analog Devices,
publication no. E1228-15-1/89.
Figure 3 shows the video waveforms associated with the current
output driving the doubly terminated 75
load of Figure 5a.
Gray Scale Operation
T he ADV7128 can be used for stand-alone, gray scale (mono-
chrome) or composite video applications (i.e., only one channel
used for video information).
Video Output Buffer
T he ADV7128 is specified to drive transmission line loads,
which is what most monitors are rated as. T he analog output
configurations to drive such loads are described in the Analog
Interface section and illustrated in Figure 5. However, in some
applications it may be required to drive long “transmission line”
cable lengths. Cable lengths greater than 10 meters can attenu-
ate and distort high frequency analog output pulses. T he inclu-
sion of output buffers will compensate for some cable distortion.
Buffers with large full power bandwidths and gains between 2
and 4 will be required. T hese buffers will 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. T hese include the AD84x series of monolithic
op amps. In very high frequency applications (80 MHz), the
AD9617 is recommended. More information on line driver buff-
ering circuits is given in the relevant op amp data sheets.
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 will result in any desired
video level.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADV7128KR30-REEL | 制造商:Analog Devices 功能描述:DAC 1-CH Segment 10-bit 28-Pin SOIC W T/R 制造商:Analog Devices 功能描述:SINGLE,10-BIT VIDEO DAC - Tape and Reel 制造商:Rochester Electronics LLC 功能描述:SINGLE,10-BIT VIDEO DAC - Tape and Reel |
| ADV7128KR50 | 制造商:Analog Devices 功能描述:DAC 1-CH Segment 10-bit 28-Pin SOIC W 制造商:Rochester Electronics LLC 功能描述:SINGLE,10-BIT VIDEO DAC - Bulk |
| ADV7128KR50-REEL | 制造商:Analog Devices 功能描述:DAC 1-CH Segment 10-bit 28-Pin SOIC W T/R 制造商:Rochester Electronics LLC 功能描述:SINGLE,10-BIT VIDEO DAC - Tape and Reel |
| ADV7128KR80 | 制造商:Analog Devices 功能描述:DAC 1-CH Segment 10-bit 28-Pin SOIC W 制造商:Rochester Electronics LLC 功能描述:SINGLE,10-BIT VIDEO DAC - Bulk 制造商:Analog Devices 功能描述:IC 10-BIT VIDEO DAC |
| ADV7128KR80-REEL | 制造商:Analog Devices 功能描述:DAC 1-CH Segment 10-bit 28-Pin SOIC W T/R 制造商:Rochester Electronics LLC 功能描述:SINGLE,10-BIT VIDEO DAC - Tape and Reel |
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