tmc1175 Cadeka Microcircuits LLC., tmc1175 Datasheet - Page 13

• Manufacturer Part Number: tmc1175
• Description: Video A/d Converter 8 Bit, 40 Msps
• Manufacturer: Cadeka Microcircuits LLC.

PRODUCT SPECIFICATION
Grounding
The TMC1175A has separate analog and digital
circuits. To keep digital system noise from the A/D
converter, it is recommended that power supply voltages
(V
V
A
pins should be individually decoupled at the pin. The digital
circuitry that gets its input from the TMC1175A should be
referred to the system digital ground plane.
Printed Circuit Board Layout
Designing with high performance mixed-signal circuits
demands printed circuits with ground planes. Wire-wrap is
not an option, even for breadboarding. Overall system per-
formance is strongly influenced by the board layout. Capac-
itive coupling from digital to analog circuits may result in
poor A/D conversion. Consider the following suggestions
when doing the layout:
1. Keep the critical analog traces (V
2. The power plane for the TMC1175A should be sepa-
3.
REV. 1.3.3 2/28/02
GND
DDA
DDD
VR-) as short as possible and as far as possible from all
digital signals. The TMC1175A should be located near
the board edge, close to the analog input connectors.
rate from that which supplies the rest of the digital cir-
cuitry. A single power plane should be used for all of
the V
is the same as that of the system's digital circuitry,
power to the TMC1175A should be decoupled with
ferrite beads and 0.1µF capacitors to reduce noise.
The ground plane should be solid, not cross-hatched.
Connections to the ground plane should have very
short leads.
) be made to the analog ground plane. Power supply
regulated, and that ground connections (D
and V
DD
0.1µF
pins. If the power supply for the TMC1175A
DDA
LM385
) originate from separate sources with
2kΩ
Gain Adjust
1kΩ
0.1mF
Figure 12. Typical Interface Circuit-High Performance
+5V
1kΩ
IN
+
-
, R
T
1kΩ
Video
Input
, R
B
20Ω
, VR+,
GND
and
75Ω
Figure 14. Typical Interface Circuit – Stabilized Reference
455Ω
RF
Input
+
-
Video
Input
Figure 13. Typical Interface Circuit – Low Cost
455Ω
Offset
Adjust
0.1µF
LM385
Wideband
Op-amp
2.2kΩ
560Ω
2V
+5V
2kΩ
Regulated +5V
56Ω
75Ω
10µF
1kΩ
0.1µF
+5V
10µF
0.1µF
1kΩ
0.1µF
R B
VR-
VR+
R T
V IN
A GND
V DDA
0.1µF
0.1µF
0.1µF
0.1µF
TMC1175A
R B
VR-
VR+
R T
V IN
R B
VR-
A GND
VR+
R T
V IN
V DDA
A GND
V DDA
TMC1175A
D GND
V DDD
TMC1175A
CONV
D 7-0
OE
D GND
+5V
D GND
+5V
V DDD
V DDD
CONV
CONV
+5V
0.1µF
27056A
D 7-0
D 7-0
OE
OE
0.1µF
TMC1175A
0.1µF
24458A
24457A
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