tmc1175 Cadeka Microcircuits LLC., tmc1175 Datasheet - Page 6

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

TMC1175A
This is the primary reason that the signal to noise ratio drops
off as full scale frequency increases. Note, also, that the slew
rate is directly proportional to signal amplitude, A. A/Ds will
handle lower-amplitude signals of higher bandwidth.
All this is of particular interest in applications such as digi-
tizing analog VGA RGB signals, or the output of a CCD
imaging chip. These data are effectively pre-sampled: there
is a period of rapid slewing from one pixel value to another,
followed by a relatively stable dc level before the signal
slews to the next pixel value. The goal is, of course, to
Equivalent Circuits and Threshold Level
6
Data or
Control
Input
Figure 6. Equivalent Analog Input Circuit
Figure 4. Equivalent Digital Input Circuit
V
IN
A
GND
V
DDA
GND
p
n
V
DD
27052A
27014B
sample on these pixel values, not on the slewing between
pixels. During the aperture time, the A/D sees essentially a
dc signal, and classic bandwidth considerations are not
important. As long as the input circuit can slew and settle to
the new value in the prescribed period, an accurate conver-
sion will be made.
The TMC1175A is capable of slewing a full 2V and settling
between samples taken as little as 25ns apart, making it ideal
for digitizing analog VGA and CCD outputs.
Figure 7. Threshold Levels for Three-State Measurements
Three-State
Outputs
OE
Figure 5. Equivalent Digital Output Circuit
t
DIS
0.5V
0.5V
p
n
V
DD
GND
High Impedance
PRODUCT SPECIFICATION
REV. 1.3.3 2/28/02
27011B
t
Output
ENA
65-1175A-07
2.0V
0.8V