tmc1175 Cadeka Microcircuits LLC., tmc1175 Datasheet - Page 12

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

TMC1175A
Typical Performance Characteristics
Applications Discussion
The circuit in Figure 12 employs a band-gap reference to
generate a variable RT reference voltages for the
TMC1175A as well as a bias voltage to offset the wideband
input amplifier to mid-range. An "offset adjust"
is also shown for varying the mid-range voltage level.
The operational amplifier in the reference circuitry is a
standard 741-type.
The voltage reference at R
volts while R
wideband amplifier output to between -0.7V and V
+0.7V. Diode protection is good practice to limit the analog
input voltage at V
12
30
25
20
15
10
50
40
30
20
10
5
0
0
0
0
Figure 10. Typical SNR vs f
B
2
is grounded. Diodes are used to restrict the
Figure 8. Typical I
IN
10
to the safe operating range.
4
T
can be adjusted from 0.0 to 2.4
20
6
DD
vs f
f s = 20 Msps
f s = 30 Msps
f s = 40 Msps
IN
8
and f
S
30
S
10
DD
40
12
The circuit in Figure 13 shows self-bias of R
connection to VR+ and VR-. This sets up a 0.6 to 2.6 Volt
input range for V
supply variation since the voltages on R
derived from V
biased at a adjustable midpoint of the A/D input range.
This circuit offers the advantage of minimum support
circuitry for the most cost-sensitive applications.
In Figure 14, an external band-gap reference sets R
Volts while R
R+, provides the bias current for the band-gap reference. The
A/D converter input is biased to the mid-point of the input
range.
60
50
40
30
20
10
50
40
30
20
10
0
0
Figure 11. Typical SNR vs Full Scale Input Range
0
0
Figure 9. Typical SFDR vs f
0.5
B
2
DDA
is grounded. The internal pull-up resistor,
IN
1.0
. The input range is susceptible to power
. The video input is AC-coupled and
4
1.5
2.0
6
PRODUCT SPECIFICATION
2.5
f s = 20 Msps
f s = 30 Msps
f s = 40 Msps
f s = 20 Msps
f s = 33 Msps
T
IN
8
and R
REV. 1.3.3 2/28/02
and f
3.0
T
and R
B
S
are directly
10
3.5
T
B
to +1.2
by
4.0
12