CDK3400 Cadeka Microcircuits LLC., CDK3400 Datasheet - Page 10

• Manufacturer Part Number: CDK3400
• Description: 10-bit, 100/150msps, Triple Video Dacs
• Manufacturer: Cadeka Microcircuits LLC.

Data Sheet
Applications Dicussion
Figure 9 below illustrates a typical CDK3400/3401 inter-
face circuit. In this example, an optional 1.2V bandgap
reference is connected to the V
internal voltage reference source.
Grounding
It is important that the CDK3400/3401 power supply is well-
Printed Circuit Board Layout
Designing with high-performance mixed-signal circuits
demands printed circuits with ground planes. Overall
system performance is strongly influenced by the board
layout. Capacitive coupling from digital to analog circuits
may result in poor D/A conversion. Consider the following
suggestions when doing the layout:
1. Keep the critical analog traces (V
2. Power plane for the CDK3400/3401 should be separate
©2009 CADEKA Microcircuits LLC
IO
from all digital signals. The CDK3400/3401 should be
located near the board edge, close to the analog out-put
connectors.
from that which supplies the digital circuitry. A single
power plane should be used for all of the V
the power supply for the CDK3400/3401 is the same
as that of the system’s digital circuitry, power to the
CDK3400/3401 should be decoupled with 0.1µF and
0.01µF capacitors and iso-lated with a ferrite bead.
R
, IO
G
) as short as possible and as far as possible
GREEN PIXEL
BLUE PIXEL
RED PIXEL
CLOCK
BLANK
INPUT
INPUT
INPUT
SYNC
R9-0
G9-0
B9-0
CLK
SYNC
BLANK
REF
REF
output, overriding the
Triple 10-bit D/A Converter
Figure 9. Typical Interface Circuit Diagram
, I
CDK3400/3401
VDD
+5V
REF
0.1µF
10µF
, COMP, IO
DD
GND
pins. If
S
,
regulated and free of high-frequency noise. Careful power
supply decoupling will ensure the highest quality video
signals at the output of the circuit. The CDK3400/3401 has
separate analog and digital circuits. To keep digital system
noise from the D/A converter, it is recommended that
power supply voltages (V
power source and all ground connections (GND) be made
to the analog ground plane. Power supply pins should be
individually decoupled at the pin.
3. The ground plane should be solid, not cross-hatched.
4. If the digital power supply has a dedicated power plane
5. CLK should be handled carefully. Jitter and noise on this
Evaluation boards are available (CEB3400 and CEB3401),
contact CADEKA for more information.
Related Products
n
n
COMP
R
V
CDK3402/3403 Triple 8-bit 100/150MSPS DACs
CDK3404 Triple 8-bit 180MSPS DAC
IO
IO
IO
REF
REF
Connections to the ground plane should have very short
leads.
layer, it should not be placed under the CDK3400/3401,
the voltage reference, or the analog outputs. Capacitive
coupling of digital power supply noise from this layer
to the CDK3400/3401 and its related analog circuitry can
have an adverse effect on performance.
clock will degrade performance. Terminate the clock line
carefully to eliminate overshoot and ringing.
R
G
B
0.1µF
560Ω
75Ω
75Ω
75Ω
+5V
3.3kΩ
(not required without external reference)
LM185-1.2
(Optional)
Green w/Sync
Z
Z
Z
o
o
o
Blue
Red
= 75Ω
= 75Ω
= 75Ω
DD
) come from the system analog
75Ω
75Ω
75Ω
0.1µF
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