TMC1203
PRODUCT SPECIFICATION
Application Notes
The circuit in Figure 10 employs a band-gap reference to
generate a variable R
TX
reference voltages for the TMC1203
as well as a bias voltage to offset the wideband input amplifi-
ers to mid-range. The operational amplifier in the reference
circuitry is a standard 741-type.
The voltage reference at R
TX
can be adjusted from 0.0 to 2.4
volts while R
BX
is grounded. Schottky diodes are used to
restrict the wideband amplifier output to between -0.3V and
V
DD
+0.3V. Diode protection is good practice to limit the
analog input voltage at V
INX
to the safe operating range.
0.1µF
LM185-1.2
0.1µF
1k�½
+5V
Gain Adjust
2k�½
0.1µF
–
1k�½
1k�½
100
GREEN
Video
Input
Wideband
Op-amp
0.1µF
VDDA
+
20�½
RTA
RTB
RTC
RBA
RBB
RBC
VINA
+5V
0.1µF
VDD
DA7-0
OEA
CLKA
+
–
1k�½
GREEN
Digital
Video
Output
75�½
10k�½
1k�½
TMC1203
+5V
DB7-0
BLUE
Digital
Video
Output
100
BLUE
Video
Input
+
–
1k�½
Wideband
Op-amp
VINB
OEB
CLKB
75�½
10k�½
1k�½
+5V
DC7-0
OEC
CLKC
VINC
AGND
DGND
RED
Digital
Video
Output
Pixel
Clock
100
RED
Video
Input
+
75�½
–
1k�½
10k�½
1k�½
Wideband
Op-amp
+5V
65-3720-07
Figure 10. Typical Interface Circuit - High Performance
Grounding
The TMC1203 has separate analog and digital circuits. To
keep digital system noise from the A/D converter, it is rec-
ommended that power supply voltages (V
DD
and V
DDA
)
come from the same source, and that ground connections
(D
GND
and A
GND
) be made to the analog ground plane, and
as close as possible to the device pins. Power supply pins
should be individually decoupled at the pin. The digital cir-
cuitry that gets its input from the TMC1203 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. Overall system
performance is strongly influenced by the board layout.
Capacitive coupling from digital to analog circuits may
result in poor A/D conversion. Consider the following sug-
gestions when doing the layout:
1.
Keep the critical analog traces (V
N
, R
TX
, R
BX
) as short
as possible and as far as possible from all digital signals.
The TMC1203 should be located close to the analog
input connectors.
12
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
