TMC1175A
PRODUCT SPECIFICATION
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
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.
Equivalent Circuits and Threshold Level
V
DD
V
DD
p
Data or
Control
Input
n
p
Output
n
GND
27014B
GND
27011B
Figure 4. Equivalent Digital Input Circuit
Figure 5. Equivalent Digital Output Circuit
V
DDA
t
ENA
V
IN
OE
Three-State
Outputs
t
DIS
0.5V
2.0V
0.8V
0.5V
65-1175A-07
A
GND
27052A
High Impedance
Figure 6. Equivalent Analog Input Circuit
Figure 7. Threshold Levels for Three-State Measurements
6
REV. 1.3.3 2/28/02
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
