TMC22191 CADEKA [Cadeka Microcircuits LLC.], TMC22191 Datasheet - Page 52

• Manufacturer Part Number: TMC22191
• Description: Digital Video Encoders/Layering Engine
• Manufacturer: CADEKA [Cadeka Microcircuits LLC.]

TMC22091/TMC22191
Applications Discussion
The TMC22x91 is a complex mixed-signal VLSI circuit. It
converts digital video signals at clock rates of up to 30 MHz
to analog video outputs. A recommended circuit connection
is shown in Figure 35.
References
The circuit shown in Figure 35 uses a stable external 1.235V
voltage reference. To use the internal voltage reference, sim-
ply delete the 3.3k resistor and the LM185-12. A simple
voltage divider from the power supply should NOT be used,
as any variations in power supply voltage would appear
directly on the video outputs.
Filtering
An simple low-pass output reconstruction filter is shown in
Figure 36. This filter is located in the video signal path after
the COMPOSITE, LUMA, and CHROMA outputs. The
value of R
52
Encoder
Figure 36. Recommended Output Reconstruction Filter
1.0 H
Video
from
75
24
5
8
REF
75
may be varied to make up for the filter loss.
OL 4-0
BYPASS
PD 23-0
VHSYNC
VVSYNC
PDC
KEY
LDV
PXCK
CVBS 7-0
GHSYNC
GVSYNC
100
BYPASS and OL 4-0
on TMC22191 only.
pF
330pF
1.8 H
27pF
MICROPROCESSOR
INTERFACE
8 2
V DO
330pF
+5V
DIGITAL VIDEO
Figure 35. Recommended Interface Circuit
0.1 F
47 F
TMC22x91
ENCODER
D GND
27025A
75
Video
Output
INTERFACE
JTAG TEST
A GND
Interface to the TMC22071 Genlocking Video
Digitizer
The TMC22x91 Digital Video Encoder has been designed to
directly interface to the TMC22071 Genlocking Video Digi-
tizer. An interface circuit is shown in Figure 37. The micro-
processor interface for TMC22x91 and TMC22071 are
similar. The R/W, RESET, D
microprocessor are shared by the TMC22x91 and
TMC22071. The CS signals are separately driven from the
microprocessor bus.
Grounding Strategy
The TMC22x91 has distinctly separate analog and digital
circuits. To minimize digital crosstalk into the analog sig-
nals, the power supplies and grounds are provided over sepa-
rate pins. In general, the best results are obtained by
connecting all grounds to a ground plane. Power supply pins
should be individually decoupled at the pin.
0.1 F
47 F
V DDA
+5V
COMPOSITE
CHROMA
COMP
LUMA
V REF
R REF
Encoder
1.0 H
Video
from
75
LM185-1.2
392
75
0.1 F
100
3.3K
pF
0
and A
LPF
LPF
LPF
330pF
V DD
1.8 H
27pF
PRODUCT SPECIFICATION
0
0.1 F
signals from the host
330pF
27007A
+5V
IN5818
COMPOSITE VIDEO
S-VIDEO OUTPUT
OUTPUT
75
Video
Output