AD ADV101KN80 Cmos 80 mhz, triple 8-bit video dac Datasheet

a
FEATURES
80 MHz Pipelined Operation
Triple 8-Bit D/A Converters
RS-343A/RS-170 Compatible Outputs
TTL Compatible Inputs
+5 V CMOS Monolithic Construction
40-Pin DIP or 44-Pin PLCC Package
Plug-In Replacement for BT101
Power Dissipation: 400 mW
APPLICATIONS
High Resolution Color Graphics
CAE/CAD/CAM Applications
Image Processing
Instrumentation
Video Signal Reconstruction
Desktop Publishing
SPEED GRADES
80 MHz
50 MHz
30 MHz
CMOS
80 MHz, Triple 8-Bit Video DAC
ADV101*
FUNCTIONAL BLOCK DIAGRAM
FS
ADJUST
VAA
VREF
REFERENCE
AMPLIFIER
ADV101
COMP
CLOCK
RED
REGISTER
8
8
GREEN
REGISTER
8
8
BLUE
REGISTER
8
8
R0
R7
PIXEL
INPUT
PORT
G0
DAC
IOR
DAC
IOG
DAC
IOB
SYNC
CONTROL
ISYNC
G7
B0
B7
REF WHITE
CONTROL
REGISTER
BLANK
SYNC
GND
GENERAL DESCRIPTION
The ADV101 is a digital-to-analog video converter on a single
monolithic chip. The part is specifically designed for high resolution color graphics and video systems. It consists of three,
high speed, 8-bit, video D/A converters (RGB); a standard TTL
input interface and high impedance, analog output, current
sources.
The ADV101 has three separate, 8-bit, pixel input ports, one
each for red, green and blue video data. Additional video input
controls on the part include sync, blank and reference white. A
single +5 V supply, an external 1.23 V reference and pixel clock
input are all that are required to make the part operational.
PRODUCT HIGHLIGHTS
1. Fast video refresh rate, 80 MHz.
2. Compatible with a wide variety of high resolution color
graphics video systems.
3. Guaranteed monotonic with a maximum differential nonlinearity of ± 0.5 LSB. Integral nonlinearity is guaranteed to be
a maximum of ± 1 LSB.
The ADV101 is capable of generating RGB video output signals, which are compatible with RS-343A and RS-170 video
standards, without requiring external buffering.
The ADV101 is fabricated in a +5 V CMOS process. Its monolithic CMOS construction ensures greater functionality with low
power dissipation. The part is packaged in both a 0.6", 40-pin
plastic DIP and a 44-pin plastic leaded (J-lead) chip carrier,
PLCC.
*ADV is a registered trademark of Analog Devices Inc.
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
= +5 V 6 5%; V = +1.235 V; R = 37.5 V, C = 10 pF; R = 560 V. I
ADV101–SPECIFICATIONS (Vconnected
to IOG. All Specifications T to T
unless otherwise noted.)
AA
REF
L
MIN
Parameter
STATIC PERFORMANCE
Resolution (Each DAC)
Accuracy (Each DAC)
Integral Nonlinearity, INL
Differential Nonlinearity, DNL
Gray Scale Error
Coding
DIGITAL INPUTS
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN2
ANALOG OUTPUTS
Gray Scale Current Range
Output Current
White Level Relative to Blank
White Level Relative to Black
Black Level Relative to Blank
Blank Level on IOR, IOB
Blank Level on IOG
Sync Level on IOG
LSB Size
DAC to DAC Matching
Output Compliance, VOC
Output Impedance, ROUT2
Output Capacitance, COUT2
VOLTAGE REFERENCE
Voltage Reference Range, VREF
Input Current, IVREF
POWER REQUIREMENTS
VAA
IAA
Power Supply Rejection Ratio
Power Dissipation
DYNAMIC PERFORMANCE
Glitch Impulse2, 3
DAC Noise2, 3, 4
Analog Output Skew
All Versions Units
L
MAX
SET
SYNC
1
Test Conditions/Comments
8
Bits
±1
± 0.5
±5
LSB max
LSB max
Guaranteed Monotonic
% Gray Scale max Max Gray Scale Current: IOG = (VREF* 12,082/RSET) mA
Max Gray Scale Current: IOR, IOB = (VREF* 8,627/RSET) mA
Binary
2
0.8
±1
10
V min
V max
µA max
pF max
15
22
mA min
mA max
17.69
20.40
16.74
18.50
0.95
1.90
0
50
6.29
9.5
0
50
69.1
2
–1
+1.4
100
30
mA min
mA max
mA min
mA max
mA min
mA max
µA min
µA max
mA min
mA max
µA min
µA max
µA typ
% typ
V min
V max
kΩ typ
pF max
1.14/1.26
+10
V min/V max
µA typ
5
125
100
0.5
625
500
V nom
mA max
mA max
%/% max
mW max
mW max
Typically 80 mA: 80 MHz Parts
Typically 70 mA: 50 MHz & 35 MHz Parts
Typically 0.12%/%: f = 1 kHz, COMP = 0.1 µF
Typically 400 mW: 80 MHz Parts
Typically 350 mW: 50 MHz & 30 MHz Parts
50
200
2
pV secs typ
pV secs typ
ns max
Typically 1 ns
VIN = 0.4 V or 2.4 V
Typically 19.05 mA
Typically 17.62 mA
Typically 1.44 mA
Typically 5 µA
Typically 7.62 mA
Typically 5 µA
IOUT = 0 mA
VREF = 1.235 V for Specified Performance
NOTES
1
Temperature Range (T MIN to T MAX); 0°C to +70°C.
2
Sample tested at +25°C to ensure compliance.
3
TTL input values are 0 to 3 volts, with input rise/fall times ≤ 3 ns, measured between the 10% and 90% points. Timing reference points at 50% for inputs and
outputs. See timing notes in Figure 1.
4
This includes effects due to clock and data feedthrough as well as RGB analog crosstalk.
Specifications subject to change without notice.
–2–
REV. B
ADV101
TIMING CHARACTERISTICS1
(VAA = +5 V 6 5%; VREF = +1.235 V; RL = 37.5 V, CL = 10 pF; RSET = 560 V.
ISYNC connected to IOG. All Specifications TMIN to TMAX2 unless otherwise noted.)
Parameter
80 MHz Version
50 MHz Version
30 MHz Version
Units
Conditions/Comments
fMAX
t1
t2
t3
t4
t5
t6
80
3
2
12.5
4
4
30
20
3
12
50
6
2
20
7
7
30
20
3
15
30
8
2
33.3
9
9
30
20
3
15
MHz max
ns min
ns min
ns min
ns min
ns min
ns max
ns typ
ns max
ns typ
Clock Rate
Data & Control Setup Time
Data & Control Hold Time
Clock Cycle Time
Clock Pulse Width High Time
Clock Pulse Width Low Time
Analog Output Delay
t7
t8 3
Analog Output Rise/Fall Time
Analog Output Transition Time
NOTES
1
TTL input values are 0 to 3 volts, with input rise/fall times ≤3 ns, measured between the 10% and 90% points. Timing reference points at 50% for inputs and outputs. See timing notes in Figure 1.
2
Temperature range (T MIN to TMAX): 0°C to +70°C.
3
Sample tested at +25°C to ensure compliance.
Specifications subject to change without notice.
t3
t4
t5
CLOCK
t1
DIGITAL INPUTS
(R0–R7, G0–G7, B0–B7;
t2
DATA
SYNC, BLANK,
REF WHITE)
t6
t8
ANALOG OUTPUTS
(IOR, IOG, IOB, I SYNC )
t7
NOTES
1. OUTPUT DELAY ( t6) MEASURED FROM THE 50% POINT OF THE RISING EDGE OF
CLOCK TO THE 50% POINT OF FULL-SCALE TRANSITION.
2. TRANSITION TIME ( t8) MEASURED FROM THE 50% POINT OF FULL-SCALE
TRANSITION TO WITHIN 2% OF THE FINAL OUTPUT VALUE.
3. OUTPUT RISE/FALL TIME ( t7) MEASURED BETWEEN THE 10% AND 90% POINTS
OF FULL TRANSITION.
Figure 1. Video Input/Output Timing
REV. B
–3–
ADV101
ABSOLUTE MAXIMUM RATINGS 1
VAA to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V
Voltage on Any Digital Pin . . . . GND – 0.5 V to VAA + 0.5 V
Ambient Operating Temperature (TA) . . . . . . . . 0°C to +70°C
Storage Temperature (TS) . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature (TJ) . . . . . . . . . . . . . . . . . . . . +150°C
Soldering Temperature (10 secs) . . . . . . . . . . . . . . . . . . 300°C
Vapor Phase Soldering (1 minute) . . . . . . . . . . . . . . . . . 220°C
IOR, IOB, IOG, ISYNC to GND2 . . . . . . . . . . . . . . 0 V to VAA
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Min
Typ
Max
Units
Power Supply
Ambient Operating
Temperature
Output Load
Reference Voltage
VAA
4.75
5.00
5.25
Volts
TA
RL
VREF
0
+70
37.5
1.235 1.26
°C
Ω
Volts
1.14
ORDERING GUIDE
NOTES
1
Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those listed in the
operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
2
Analog output short circuit to any power supply or common can be of an indefinite
duration.
1
Speed
50 MHz
Package
Option2
80 MHz
Plastic DIP
(N-40A)
ADV101KN80 ADV101KN50 ADV101KN30
PLCC3
(P-44A)
ADV101KP80
30 MHz
ADV101KP50
ADV101KP30
NOTES
1
All devices are specified for 0°C to +70°C operation.
2
N = Plastic DIP; P = Plastic Leaded Chip Carrier.
3
PLCC: Plastic Leaded Chip Carrier (J-lead).
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADV101 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
PIN CONFIGURATIONS
35 GND
B6 7
ADV101
34 IOB
B5 8
TOP VIEW
(NOT TO SCALE)
33 IOR
31 ISYNC
30 VAA
29 GND
B1 13
28 FS ADJUST
B2 14
27 VREF
B3 15
26 COMP
B5
B6
41
40
7
39 B7
R0
8
38 R4
R1
9
37 R5
36 R6
R3 11
ADV101
35 R7
G0 12
TOP VIEW
(Not to Scale)
34 G4
G1 13
33 G5
G2 14
32 G6
G3 15
31 G7
30 BLANK
REF WHITE 16
29 SYNC
COMP 17
–4–
22
23
24
25
26
27
28
GND
21 G0
21
IOB
22 G1
R3 20
20
IOR
23 G2
R2 19
19
IOG
R1 18
VREF
18
24 G3
VAA
25 REF WHITE
R0 17
ISYNC
CLOCK 16
42
R2 10
32 IOG
B0 12
43
VAA
GND 11
44
GND
VAA 10
1
GND
B4 9
2
CLOCK
FS ADJUST
B7 6
3
B4
36 SYNC
4
VAA
37 BLANK
R4 5
5
GND
R5 4
6
B0
38 G7
GND
R6 3
B1
39 G6
B3
40 G5
R7 2
B2
G4 1
VAA
PLCC
DIP
REV. B
ADV101
PIN FUNCTION DESCRIPTION
Pin
Mnemonic
BLANK
SYNC
CLOCK
REF WHITE
R0–R7,
G0–G7,
B0–B7
IOR, IOG, IOB
ISYNC
FS ADJUST
COMP
VREF
VAA
GND
REV. B
Function
Composite blank control input (TTL compatible). A logic zero on this control input drives the analog outputs,
IOR, IOB and IOG, to the blanking level. The BLANK signal is latched on the rising edge of CLOCK. While
BLANK is a logical zero, the R0–R7, G0–G7, R0–R7 and REF WHITE pixel and control inputs are ignored.
Composite sync control input (TTL compatible). A logical zero on the SYNC input; switches off a 40 IRE current source on the ISYNC output. SYNC does not override any other control or data input, therefore, it should
only be asserted during the blanking interval. SYNC is latched on the rising edge of CLOCK.
Clock input (TTL compatible). The rising edge of CLOCK latches the R0–R7, G0–G7, B0–B7, SYNC,
BLANK and REF WHITE pixel and control inputs. It is typically the pixel clock rate of the video system.
CLOCK should be driven by a dedicated TTL buffer.
Reference white control input (TTL compatible). A logical one on this input forces the IOR, IOG and IOB outputs to the white level, regardless of the pixel input data (R0–R7, G0–G7 and B0–B7) REF WHITE is latched
on the rising edge of clock.
Red, green and blue pixel data inputs (TTL compatible). Pixel data is latched on the rising edge of CLOCK. R0,
G0 and B0 are the least significant data bits. Unused pixel data inputs should be connected to either the regular
PCB power or ground plane.
Red, green and blue current outputs. These high impedance current sources are capable of directly driving a
doubly terminated 75 Ω coaxial cable. All three current outputs should have similar output loads whether or not
they are all being used.
Sync current output. This high impedance current source can be directly connected to the IOG output. This allows sync information to be encoded onto the green channel. ISYNC does not output any current while SYNC is
at logical zero. The amount of current output at ISYNC while SYNC is at logical one is given by:
ISYNC (mA) = 3,455 × VREF (V)/RSET (Ω)
If sync information is not required on the green channel, ISYNC should be connected to AGND.
Full-scale adjust control. A resistor (RSET) connected between this pin and GND, controls the magnitude of the
full-scale video signal. Note that the IRE relationships are maintained, regardless of the full-scale output current.
The relationship between RSET and the full-scale output current on IOG (assuming ISYNC is connected to IOG)
is given by:
RSET (Ω) = 12,082 × VREF (V)/IOG (mA)
The relationship between RSET and the full-scale output current on IOR and IOB is given by:
IOR, IOB (mA) = 8,628 × VREF (V)/ RSET (Ω)
Compensation pin. This is a compensation pin for the internal reference amplifier. A 0.1 µF ceramic capacitor
must be connected between COMP and VAA.
Voltage reference input. An external 1.2 V voltage reference must be connected to this pin. The use of an external resistor divider network is not recommended. A 0.1 µF decoupling ceramic capacitor should be connected
between VREF and VAA.
Analog power supply (5 V ± 5%). All VAA pins on the ADV101 must be connected.
Ground. All GND pins must be connected.
–5–
ADV101
TERMINOLOGY
Raster Scan
Blanking Level
The level separating the SYNC portion from the video portion
of the waveform. Usually referred to as the front porch or back
porch. At 0 IRE units, it is the level which will shut off the picture tube, resulting in the blackest possible picture.
The most basic method of sweeping a CRT one line at a time to
generate and display images.
Color Video (RGB)
The maximum positive polarity amplitude of the video signal.
Reference Black Level
The maximum negative polarity amplitude of the video signal.
Reference White Level
This usually refers to the technique of combining the three primary colors of red, green and blue to produce color pictures
within the usual spectrum. In RGB monitors, three DACs are
required, one for each color.
Sync Level
The peak level of the SYNC signal.
Video Signal
That portion of the composite video signal which varies in gray
scale levels between reference white and reference black. Also referred to as the picture signal, this is the portion which may be
visually observed.
Sync Signal (SYNC)
The position of the composite video signal which synchronizes
the scanning process.
Gray Scale
The discrete levels of video signal between reference black and
reference white levels. An 8-bit DAC contains 256 different levels, while a 6-bit DAC contains 64.
The REF WHITE control input drives the RGB video outputs
to the white level. This function could be used to overlay a cursor or crosshair onto the RGB video output.
CIRCUIT DESCRIPTION AND OPERATION
The ADV101 contains three 8-bit D/A converters, with three
input channels, each containing an 8-bit register. Also integrated on board the part is a reference amplifier and CRT control functions BLANK, SYNC and REF WHITE.
Table I details the resultant effect on the analog outputs of
BLANK, SYNC and REF WHITE.
Digital Inputs
All these digital inputs are specified to accept TTL logic levels
24-bits of pixel data (color information) R0–R7, G0–G7 and
B0–B7 are latched into the device on the rising edge of each
clock cycle. This data is presented to the three 8-bit DACs and
is then converted to three analog (RGB) output waveforms.
(See Figure 2.)
Clock Input
The CLOCK input of the ADV101 is typically the pixel clock
rate of the system. It is also known as the dot rate. The dot rate
and hence the required CLOCK frequency, will be determined
by the on-screen resolution, according to the following equation.
Three other digital control signals are latched to the analog
video outputs in a similar fashion. BLANK, SYNC and REF
WHITE are each latched on the rising edge of CLOCK to
maintain synchronization with the pixel data stream.
Dot Rate = (Horiz Res) × (Vert Res) × (Refresh Rate)/
Dot Rate = (Retrace Factor)
The BLANK and SYNC functions allow for the encoding of
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 and SYNC digital inputs. Figure 3 shows the analog
output, RGB video waveform of the ADV101. The influence of
SYNC and BLANK on the analog video waveform is illustrated.
Horiz Res
= Number of pixels/line
Vert Res
= Number of lines/frame
Refresh Rate
= 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
= Total blank time factor. This takes into account that the display is blanked for a certain
fraction of the total duration of each frame
(e.g., 0.8).
CLOCK
DIGITAL INPUTS
DATA
(R0–R7, G0–G7, B0–B7;
SYNC, BLANK,
REFWHITE)
ANALOG OUTPUTS
(IOR, IOG, IOB, ISYNC )
Figure 2. Video Data Input/Output
–6–
REV. B
ADV101
If we, therefore, have a graphics system with a 1024 × 1024
resolution, a noninterlaced 60 Hz refresh rate and a retrace factor of 0.8, then:
The required CLOCK frequency is thus 78.6 MHz.
All video data and control inputs are latched into the ADV101
on the rising edge of CLOCK, as previously described in the
“Digital Inputs” section. It is recommended that the CLOCK
input to the ADV101 be driven by a TTL buffer (e.g., 74F244).
Dot Rate = 1024 × 1024 × 60/0.8
Dot Rate = 78.6 MHz
RED, BLUE
GREEN
mA
V
mA
V
19.05
0.714
26.67
1.000
WHITE LEVEL
92.5 IRE
1.44
0.054
9.05
0.340
7.62
0.286
BLACK LEVEL
7.5 IRE
0
0
BLANK LEVEL
40 IRE
0
0
SYNC LEVEL
NOTES
1. OUTPUTS CONNECTED TO A DOUBLY TERMINATED 75Ω LOAD.
2. VREF = 1.235V, R SET = 560Ω, I SYNC CONNECTED TO IOG.
3. RS-343A LEVELS AND TOLERANCES ASSUMED ON ALL LEVELS.
Figure 3. RGB Video Output Waveform
Table I. Video Output Truth Table
Description
IOG
(mA)1
IOR, IOB
(mA)
REF
WHITE
SYNC
BLANK
DAC
Input Data
WHITE LEVEL
WHITE LEVEL
VIDEO
VIDEO to BLANK
BLACK LEVEL
BLACK to BLANK
BLANK LEVEL
SYNC LEVEL
26.67
26.67
video + 9.05
video + 1.44
9.05
1.44
7.62
0
19.05
19.05
video + 1.44
video + 1.44
1.44
1.44
0
0
1
0
0
0
0
0
0
0
1
1
1
0
1
0
1
0
1
1
1
1
1
1
0
0
xxH
FFH
data
data
00H
00H
xxH
xxH
NOTE
1
Typical with full-scale IOG = 26.67 mA. VREF = 1.235 V, R SET = 560 Ω, ISYNC connected to IOG.
Video Synchronization and Control
Reference Input
The ADV101 has a single composite video sync (SYNC) input
control. Many graphics processors and CRT controllers have
the ability of generating horizontal sync (HSYNC), vertical sync
(VSYNC) and composite SYNC.
An external 1.23 V voltage reference is required to drive the
ADV101. The AD589 from Analog Devices is an ideal choice of
reference. It is a two-terminal, low cost, temperature compensated bandgap voltage reference which provides a fixed 1.23 V
output voltage for input currents between 50 µA and 5 mA. Figure 4 shows a typical reference circuit connection diagram. The
voltage reference gets its current drive from the ADV101’s VAA
through an external 1 kΩ resistor to the VREF pin. A 0.1 µF ceramic capacitor is required between the COMP and VAA. This is
necessary so as to provide compensation for the internal reference amplifier.
In a graphics system which does not automatically generate a
composite SYNC signal, the inclusion of some additional logic
circuitry will enable the generation of a composite SYNC signal.
The ISYNC current output is typically connected directly to the
IOG output, thus encoding video synchronization information
onto the green video channel. If it is not required to encode sync
information onto the ADV101, the SYNC input should be tied
to logic low and ISYNC should be connected to analog GND.
REV. B
–7–
ADV101
A resistance RSET connected between FS ADJUST and GND
determines the amplitude of the output video level according to
the following equations:
IOR, IOG, IOB
Z O = 75Ω
DACs
(CABLE)
IOG (mA) = 12,082 × VREF (V)/RSET (Ω)
(1)
IOR, IOB (mA) = 8,628 × VREF (V)/RSET (Ω)
(2)
Z L= 75Ω
Z S = 75Ω
(MONITOR)
(SOURCE
TERMINATION)
If SYNC is not being encoded onto the green channel, then
Equation 1 will be similar to Equation 2.
Using a variable value of RSET, as shown in Figure 4, allows for
accurate adjustment of the analog output video levels. Use of a
fixed 560 Ω RSET resistor yields the analog output levels as
quoted in the specification page. These values also correspond
to the RS-343A video waveform values as shown in Figure 3.
TERMINATION REPEATED THREE TIMES
FOR RED, GREEN AND BLUE DACs
Figure 5a. Analog Output Termination for RS-343A
IOR, IOG, IOB
ANALOG POWER PLANE
+5V
0.1µF
Z O = 75Ω
DACs
(CABLE)
Z S = 150Ω
COMP
(SOURCE
TERMINATION)
VAA
(MONITOR)
I REF ~
~ 4mA
1kΩ
VREF
TERMINATION REPEATED THREE TIMES
FOR RED, GREEN AND BLUE DACs
TO DACs
FS ADJUST
Figure 5b. Analog Output Termination for RS-170
AD589
500Ω
RSET
560Ω
required configuration for each of the three RGB outputs connected into a doubly terminated 75 Ω load. This arrangement
will develop RS-343A video output voltage levels across a 75 Ω
monitor.
(1.235V
VOLTAGE
REFERENCE)
100Ω
GND
ADV101*
Z L= 75Ω
A suggested method of driving RS-170 video levels into a 75 Ω
monitor is shown in Figure 5b. The output current levels of the
DACs remain unchanged, but the source termination resistance,
ZS, on each of the three DACs is increased from 75 Ω to 150 Ω.
*ADDITIONAL CIRCUITRY, INCLUDING
DECOUPLING COMPONENTS,
EXCLUDED FOR CLARITY
More detailed information regarding load terminations for various output configurations, including RS-343A and RS-170, is
available in an application note entitled “Video Formats &
Required Load Terminations” available from Analog Devices,
publication number E1228-15-1/89.
Figure 4. Reference Circuit
D/A Converters
The ADV101 contains three matched 8-bit D/A converters. The
DACs are designed using an advanced, high speed, segmented
architecture. The 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. As all this circuitry is on one monolithic device, matching between the three
DACs is optimized. As well as matching, the use of identical
current sources in a monolithic design guarantees monotonicity
and low glitch. The onboard operational amplifier stabilizes the
full-scale output current against temperature and power supply
variations.
Figure 3 shows the video waveforms associated with the three
RGB outputs driving the doubly terminated 75 Ω load of Figure
5a. As well as the gray scale levels, black level to white level, the
diagram also shows the contributions of SYNC and BLANK.
These control inputs add appropriately weighted currents to the
analog outputs, producing the specific output level requirements
for video applications. Table I details how the SYNC and
BLANK inputs modify the output levels.
Gray Scale Operation
The ADV101 can be used for stand-alone, gray scale (monochrome) or composite video applications (i.e., 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 logical zero.
Analog Outputs
The ADV101 has three analog outputs, corresponding to the
red, green and blue video signals. A fourth analog output
(ISYNC) can be used if it is required to encode video synchronization information onto the green signal. In this case, ISYNC is
connected to IOG. (See “Video Synchronization and Control”
section.)
The red, green and blue analog outputs of the ADV101 are high
impedance current sources. Each one of these three RGB current outputs is capable of directly driving a 37.5 Ω load, such as
a doubly terminated 75 Ω coaxial cable. Figure 5a shows the
–8–
REV. B
ADV101
The unused analog outputs should be terminated with the same
load as that for the used channel. In other words, if the red
channel is used and IOR is terminated with a doubly terminated 75 Ω load (37.5 Ω), IOB and IOG should be terminated
with 37.5 Ω resistors. (See Figure 6.)
VIDEO
INPUT
The ADV101 is specified to drive transmission line loads, which
is what most monitors are rated as. The 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 attenuate and
distort high frequency analog output pulses. The inclusion of
output buffers will compensate for some cable distortion. Buffers with large full power bandwidths and gains between 2 and 4
will be required. These 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. These include the AD84X series of monolithic op
amps. In very high frequency applications (80 MHz), the
AD9617 is recommended. More information on line driver buffering circuits is given in the relevant op amp data sheets.
DOUBLY
TERMINATED
75Ω LOAD
IOR
R0
Video Output Buffers
R7
IOG
G0
37.5Ω
G7
B0
IOB
B7
37.5Ω
ADV101
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.
GND
Figure 6. Input and Output Connections for Stand-Alone
Gray Scale or Composite Video
Z2
Z1
+V
S
IOR, IOG, IOB
2
0.1µF
Z O = 75Ω
7
AD848 6
DACs
Z S = 75Ω
(SOURCE
TERMINATION)
3
4
75Ω
0.1µF
(CABLE)
Z1
GAIN (G) = 1 +
Z2
Figure 7. AD848 As an Output Buffer
REV. B
Z L= 75Ω
(MONITOR)
–V
S
–9–
ADV101
PC BOARD LAYOUT CONSIDERATIONS
Ground Planes
The ADV101 is optimally designed for lowest noise performance, both radiated and conducted noise. To complement the
excellent noise performance of the ADV101, it is imperative
that great care be given to the PC board layout. Figure 8 shows
a recommended connection diagram for the ADV101.
The ADV101, and associated analog circuitry, should have a
separate ground plane referred to as the analog ground plane.
This ground plane should connect to the regular PCB ground
plane at a single point through a ferrite bead, as illustrated in
Figure 8. This bead should be located as close as possible
(within 3 inches) to the ADV101.
The layout should be optimized for lowest noise on the
ADV101 power and ground lines. This can be achieved by
shielding the digital inputs and providing good decoupling. The
lead length between groups of VAA and GND pins should by
minimized so as to minimize inductive ringing.
The analog ground plane should encompass all ADV101
ground pins, voltage reference circuitry, power supply bypass
circuitry, the analog output traces and any output amplifiers.
The regular PCB ground plane area should encompass all the
digital signal traces, excluding the ground pins, leading up to
the ADV101.
COMP
C6
0.1µF
R0
ANALOG POWER PLANE
R7
VIDEO
DATA
INPUTS
VAA
G0
G7
L1 (FERRITE BEAD)
C3
0.1µF
B0
B7
C4
0.1µF
R4
1kΩ
C5
0.1µF
VREF
Z1 (AD589)
ADV101
+ 5V (VCC )
C1
33µF
C2
10µF
ANALOG GROUND PLANE
GND
GROUND
RSET
560Ω
R1
75Ω
R2
75Ω
R3
75Ω
L2 (FERRITE BEAD)
FS ADJUST
CLOCK
IOR
VIDEO
CONTROL
INPUTS
REF WHITE
RGB
VIDEO
OUTPUT
IOG
SYNC
ISYNC
IOB
BLANK
COMPONENT
C1
C2
C3, C4, C5, C6
L1, L2
R1, R2, R3
R4
RSET
Z1
DESCRIPTION
33µF TANTALUM CAPACITOR
10µF TANTALUM CAPACITOR
0.1µF CERAMIC CAPACITOR
FERRITE BEAD
75Ω 1% METAL FILM RESISTOR
1kΩ 1% METAL FILM RESISTOR
560Ω 1% METAL FILM RESISTOR
1.235V VOLTAGE REFERENCE
VENDOR PART NUMBER
FAIR-RITE 27430011 OR MURATA BL01/02/03
DALE CMF-55C
DALE CMF-55C
DALE CMF-55C
ANALOG DEVICES AD589JH
Figure 8. Typical Connection Diagram and Component List
–10–
REV. B
ADV101
Power Planes
Digital Signal Interconnect
The PC board layout should have two distinct power planes,
one for analog circuitry and one for digital circuitry. The analog
power plane should encompass the ADV101 (VAA) and all associated analog circuitry. This power plane should be connected
to the regular PCB power plane (VCC) at a single point through
a ferrite bead, as illustrated in Figure 8. This bead should be located within three inches of the ADV101.
The digital signal lines to the ADV101 should be isolated 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
ADV101 should be avoided so as to minimize noise pickup.
The PCB power plane should provide power to all digital logic
on the PC board, and the analog power plane should provide
power to all ADV101 power pins, voltage reference circuitry and
any output amplifiers.
The PCB power and ground planes should not overlay portions
of the analog power plane. Keeping the PCB power and ground
planes from overlaying the analog power plane will contribute to
a reduction in plane-to-plane noise coupling.
Supply Decoupling
Noise on the analog power plane can be further reduced by the
use of multiple decoupling capacitors. (See Figure 8.)
Optimum performance is achieved by the use of 0.1 µF ceramic
capacitors. Each of the two groups of VAA should be individually
decoupled to ground. This should be done 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 ADV101 contains circuitry
to reject power supply noise, this rejection decreases with frequency. If a high frequency switching power supply is used, the
designer should pay close attention to reducing power supply
noise. A dc power supply filter (Murata BNX002) will provide
EMI suppression between the switching power supply and the
main PCB. Alternatively, consideration could be given to using
a three-terminal voltage regulator.
REV. B
Any active pull-up termination resistors for the digital inputs
should be connected to the regular PCB power plane (VCC), and
not the analog power plane.
Analog Signal Interconnect
The ADV101 should be located as close as possible to the output connectors thus minimizing noise pickup and reflections
due to impedance mismatch.
The video output signals should overlay the ground plane, and
not the analog power plane, thereby maximizing the high frequency power supply rejection.
For optimum performance, the analog outputs should each have
a source termination resistance to ground of 75 Ω (doubly
terminated 75 Ω configuration). This termination resistance
should be as close as possible to the ADV101 so as to minimize
reflections.
Additional information on PCB design is available in an application note entitled “Design and Layout of a Video Graphics System for Reduced EMI.” This application note is available from
Analog Devices, publication number E1309–15–10/89.
–11–
ADV101
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
C1380–24–4/90
44-Terminal Plastic Leaded Chip Carrier
(P-44A)
PRINTED IN U.S.A.
40-Pin Plastic DIP
(N-40A)
–12–
REV. B
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