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TMC3503
Triple Video D/A Converter
8 bit, 80 Msps, 5V
Features
•
•
•
•
•
•
•
8-bit resolution
80, 50, and 30 megapixels per second
±0.5 LSB linearity error
Sync, blank, and white controls
Independent sync current output
1.0V p-p video into 37.5Ω or 75Ω load
Enhancemenet of ADV7120
– Internal bandgap voltage reference
– Double-buffered data for low distortion
– Power-down sleep mode
Double-buffered data for low distortion
TTL-compatible inputs
Low glitch energy
Single +5 Volt power supply
Description
The TMC3503 is a high-speed triple 8-bit D/A converter
especially suited for video and graphics applications.
It offers 8-bit resolution, TTL-compatible inputs, low power
consumption, a power-down sleep mode, and requires only a
single +5 Volt power supply. It has single-ended current
outputs, SYNC and BLANK control inputs, and a separate
current source for adding sync pulses to any D/A converter
output. WHITE and SLEEP control inputs are available on
PLCC parts. It is ideal for generating analog RGB from
digital RGB and driving computer display and video moni-
tors. Three speed grades are available: 30, 50, and 80 Msps.
The TMC3503 triple D/A converter is available in a 44-lead
plastic J-leaded PLCC. It is also available in a 48-lead plastic
LQFP package. It is fabricated on a sub-micron CMOS
process with performance guaranteed from 0°C to 70°C.
•
•
•
•
Applications
• Video signal conversion
– RGB
– YC
B
C
R
– Composite, Y, C
• Multimedia systems
• Image processing
• True-color graphics systems
• Broadcast television equipment
• High-Definition Television (HDTV) equipment
• Direct digital synthesis
Block Diagram
SYNC
BLANK
WHITE [PLCC only]
8
SYNC
IO
S
[LQFP only]
8 bit D/A
Converter
IO
G
G
7-0
B
7-0
8
8 bit D/A
Converter
IO
B
R
7-0
SLEEP [PLCC only]
CLOCK
8
8 bit D/A
Converter
IO
R
COMP
R
REF
V
REF
65-3503-01
+1.235V
Ref
REV. 1.02 11/24/99
TMC3503
PRODUCT SPECIFICATION
Functional Description
The TMC3503 is a low-cost triple 8-bit CMOS D/A con-
verter designed to directly drive computer CRT displays at
pixel rates up to 80 Msps. It comprises three identical 8-bit
D/A converters with registered data inputs, common clock,
and internal voltage reference. An independent current
source allows sync to be added to any D/A converter output.
SLEEP
The SLEEP control, when HIGH, places the TMC3503 in a
power-down state. This function operates asynchronously.
D/A Outputs
Each D/A output is a current source. To obtain a voltage out-
put, a resistor must be connected to ground. Output voltage
depends upon this external resistor, the reference voltage,
and the value of the gain-setting resistor connected between
R
REF
and GND.
Normally, a source termination resistor of 75 Ohms is con-
nected between the D/A current output pin and GND near
the D/A converter. A 75 Ohm coaxial cable may then be con-
nected with another 75 Ohm termination resistor at the far
end of the cable. This "double termination" presents the D/A
converter with a net resistive load of 37.5 Ohms.
The TMC3503 may also be operated with a single 75 Ohm
terminating resistor. To lower the output voltage swing to the
desired range, the value of the resistor on R
REF
should be
increased.
Digital Inputs
All digital inputs are TTL-compatible. Data are registered on
the rising edge of the CLK signal. The analog output
changes t
DO
after the rising edge of CLK. There is one stage
of pipeline delay on the chip. The guaranteed clock rates of
the TMC3503 are 80, 50, and 30 MHz.
SYNC and BLANK
SYNC and BLANK inputs control the output level
(Figure 1 and Table 1) of the D/A converters during CRT
retrace intervals. BLANK forces the D/A outputs to the
blanking level while SYNC turns off a separate current
source which is brought off the chip through the IO
S
pin.
data: 660 mV max.
Voltage Reference
The TMC3503 has an internal bandgap voltage reference of
+1.235 Volts. An external voltage reference may be con-
nected to the V
REF
pin, overriding the internal voltage refer-
ence. All three D/A converters are driven from the same
reference.
A 0.1µF capacitor must be connected between the COMP
pin and V
DD
to stabilize internal bias circuitry and ensure
low-noise operation.
pedestal: 54 mV
sync: 286 mV
65-3503-02
Figure 1. Nominal Output Levels
IO
S
may be connected to any one D/A output, or used inde-
pendently. It is commonly tied to the green D/A converter for
“Sync on Green” operation. This connection adds a 40 IRE
sync pulse to the D/A output and brings that D/A output to
0.0 Volts during the sync tip. SYNC and BLANK are regis-
tered on the rising edge of CLK.
BLANK gates the D/A inputs and sets the pedestal voltage.
If BLANK = HIGH, the D/A inputs are added to a pedestal
which offsets the current output. If BLANK = LOW, data
inputs and the pedestal are disabled.
Power and Ground
The TMC3503 D/A converter requires a single +5.0 Volt
power supply. The analog (V
DD
) power supply voltage
should be decoupled to GND to reduce power supply
induced noise. 0.1µF decoupling capacitors should be placed
as close as possible to the power pins.
The high slew-rate of digital data makes capacitive coupling
to the outputs of any D/A converter a potential problem.
Since the digital signals contain high-frequency components
of the CLK signal, as well as the video output signal, the
resulting data feedthrough often looks like harmonic distor-
tion or reduced signal-to-noise performance. All ground pins
should be connected to a common solid ground plane for
best performance.
WHITE
The WHITE control drives all three D/As to full-scale, over-
riding the data inputs. It is overridden by the BLANK input,
and is independent of SYNC.
2
REV. 1.02 11/24/99
PRODUCT SPECIFICATION
TMC3503
Table 1. Output Voltage versus Input Code, SYNC, BLANK, and WHITE
V
REF
= 1.235 V, R
REF
= 590
Ω,
R
L
= 37.5
Ω
RGB7-0
(MSB…LSB)
XXXX XXXX
1111 1111
1111 1110
1111 1101
•
•
0000 0000
1111 1111
•
•
0000 0010
0000 0001
0000 0000
XXXX XXXX
XXXX XXXX
All D/As
SYNC
X
X
X
X
•
•
X
X
•
•
X
X
X
X
X
BLANK
1
1
1
1
•
•
1
1
•
•
1
1
1
0
0
WHITE
1
0
0
0
•
•
0
0
•
•
0
0
0
X
X
V
OUT
0.714
0.714
0.711
0.709
•
•
0.385
0.383
•
•
0.059
0.057
0.054
0.000
0.000
SYNC
1
1
1
1
•
•
1
1
•
•
1
1
1
1
0
D/A with IOS Connected
BLANK
1
1
1
1
•
•
1
1
•
•
1
1
1
0
0
WHITE
1
0
0
0
•
•
0
0
•
•
0
0
0
X
X
V
OUT
1.000
1.000
0.997
0.995
•
•
0.671
0.669
•
•
0.345
0.343
0.340
0.286
0.000
Pin Assignments
PLCC Package
R
7
R
6
R
5
R
4
R
3
R
2
R
1
R
0
R
REF
V
REF
COMP
LQFP Package
GND
R
7
R
6
R
5
R
4
R
3
R
2
R
1
R
0
GND
GND
NC
38
37
36
35
48
47
46
45
44
43
42
41
40
39
38
37
39
44
43
42
41
18
19
20
21
22
23
24
25
26
27
28
G
0
G
1
G
2
G
3
G
4
G
5
G
6
G
7
BLANK
SYNC
V
DD
40
6
5
4
3
2
1
7
8
9
10
11
12
13
14
15
16
17
TMC3503
34
33
32
31
30
29
IO
R
IO
G
IO
S
V
DD
V
DD
V
DD
IO
B
GND
GND
GND
GND
GND
G
0
G
1
G
2
G
3
G
4
G
5
G
6
G
7
BLANK
SYNC
V
DD
1
2
3
4
5
6
7
8
9
10
11
12
TMC3503
36
35
34
33
32
31
30
29
28
27
26
25
R
REF
V
REF
COMP
IO
R
IO
G
OV
DD
V
DD
IO
B
GND
GND
CLOCK
NC
B
0
B
1
B
2
B
3
B
4
B
5
B
6
B
7
WHITE
CLK
SLEEP
65-3503-03
13
14
15
16
17
18
19
20
21
22
23
24
65-3503-06
Notes (LQFP Package Only):
1. Pin functions White and Sleep are not available.
2. IO
S
function is tied internally to IO
G
pin.
NC
GND
GND
B
0
B
1
B
2
B
3
B
4
B
5
B
6
B
7
NC
REV. 1.02 11/24/99
3
TMC3503
PRODUCT SPECIFICATION
Pin Descriptions
Pin
Name
CLK
Pin Number
LQFP
26
PLCC
27
Value
TTL
Pin Function Description
Clock Input.
The clock input is TTL-compatible and all pixel
data is registered on the rising edge of CLK. It is recommended
that CLK be driven by a dedicated TTL buffer to avoid reflection
induced jitter, overshoot, and undershoot.
Red, Green, and Blue Pixel Inputs.
The R, G, and B digital
inputs are TTL-compatible and registered on the rising edge of
CLK.
Sync Pulse Input.
Bringing SYNC LOW, turns off a 40 IRE
(7.62 mA) current source which forms a sync pulse on any D/A
converter output connected to IO
S
. SYNC is registered on the
rising edge of CLK along with pixel data and has the same
pipeline latency as BLANK and pixel data. SYNC does not
override any other data and should be used only during the
blanking interval. If the system does not require sync pulses,
SYNC and IO
S
should be connected to GND.
Blanking Input.
When BLANK is LOW, pixel inputs are ignored
and the D/A converter outputs are driven to the blanking level.
BLANK is registered on the rising edge of CLK and has the
same two-pipe latency as SYNC and Data.
Force Full Scale Input.
When WHITE is HIGH, pixel inputs are
ignored and the D/A converter outputs are driven to their full-
scale output level. A BLANK input overwrites a WHITE input.
WHITE is register on the rising edge of CLK and has the same
two-pipe latency as SYNC and Data.
Power-down Control Input.
When HIGH, SLEEP places the D/
A converter in a low-power-dissipation mode. The D/A current
sources and the digital processing are disabled. The last data
loaded into the input and D/A registers is retained. This control is
asynchronous.
Red, Green, and Blue Data Outputs.
The current source
outputs of the D/A converters are capable of driving RS-343A/
SMPTE-170M compatible levels into doubly-terminated 75 Ohm
lines. Sync pulses may be added to any D/A output.
SYNC Current Output.
When this pin is connected to any of the
D/A converter outputs, a 40 IRE offset is added to the video
level. When the SYNC input is LOW, the current is turned off,
bring the sync tip voltage to 0.0V. If no sync pulse is required,
IO
S
should be grounded. When SYNC is HIGH, the current
flowing out of IO
S
is:
IO
S
= 3.64 (V
REF
/ R
REF
)
Voltage Reference
V
REF
35
41
+1.235 V
Voltage Reference Input/Output.
An internal voltage source of
+1.235 Volts is output on this pin. An external +1.235 Volt
reference may be applied here which overrides the internal
reference. Decoupling V
REF
to GND with a 0.1µF ceramic
capacitor is required.
Clock and Pixel I/O
R
7-0
G
7-0
B
7-0
Controls
SYNC
47-40
9-2
23-16
11
6-1, 44-43
14-7
25-18
16
TTL
TTL
BLANK
10
15
TTL
WHITE
—
26
TTL
SLEEP
—
28
TTL
Video Outputs
IO
R
IO
G
IO
B
IO
S
33
32
29
32
(connected
to IO
G
)
39
38
33
37
0.714 V
p-p
0.714 V
p-p
4
REV. 1.02 11/24/99
PRODUCT SPECIFICATION
TMC3503
Pin Descriptions
(continued)
Pin
Name
R
REF
Pin Number
LQFP
36
PLCC
42
Value
590
Ω
Pin Function Description
Current-setting Resistor.
The full-scale output current of each
D/A converter is determined by the value of the resistor
connected between R
REF
and GND. The nominal value for
R
REF
is found from:
R
REF
= 9.1 (V
REF
/I
FS
)
where I
FS
is the full-scale (white) output current (amps) from the
D/A converter (without sync). Sync is 0.4 I
FS
.
D/A full-scale (white) current may also be calculated from:
I
FS
= V
FS
/R
L
Where V
FS
is the white voltage level and R
L
is the total resistive
load (ohms) on each D/A converter. V
FS
is the blank to full-scale
voltage.
COMP
34
40
0.1 µF
Compensation Capacitor.
A 0.1 µF ceramic capacitor must be
connected between COMP and V
DD
to stabilize internal bias
circuitry.
Power Supply.
Ground.
Power, Ground
V
DD
GND
12, 30, 31 17, 34–36
1, 14, 15,
27, 28, 38,
39, 48
13, 24, 25,
37
29–32
+5 V
0.0V
NC
—
—
No Connect
Equivalent Circuits
V
DD
V
DD
p
Digital
Input
n
OUT
GND
GND
27014D
27013B
n
V
DD
p
Figure 2. Equivalent Digital Input Circuit Figure 3. Equivalent Analog Output Circuit
REV. 1.02 11/24/99
5
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