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參數(shù)資料
| 型號(hào)： | TMC1273 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | 8 bit, 20 Msps, 3V Power Supply Video A/D Converter(8位,20Msps, 3V 電源視頻A/D轉(zhuǎn)換器) |
| 中文描述： | 8位，20 MSPS的3V的電源供應(yīng)器視頻A / D轉(zhuǎn)換器（8位，20Msps，3V的電源視頻的A / D轉(zhuǎn)換器） |
| 文件頁數(shù)： | 12/20頁 |
| 文件大?。?/td> | 98K |
| 代理商： | TMC1273 |
PRODUCT SPECIFICATION
TMC1173A/TMC1273
12
P
Applications Discussion
The circuit in Figure 12 employs a band-gap reference to
generate a variable RT reference voltages for the
TMC1173A/1273 as well as a bias voltage to offset the
inverting 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
T
can be adjusted from 0.0 to 2.4
volts while R
B
is grounded. Diodes are used to restrict the
wideband amplifier output to between -0.7V and V
DD
+0.7V. Diode protection is good practice to limit the analog
input voltage at V
IN
to the safe operating range.
The circuit in Figure 13 shows self-bias of R
T
and R
B
by
connection to VR+ and VR-. This sets up a 0.4 to 1.7 Volt
input range for V
IN
. The input range is susceptible to power
supply variation since the voltages on R
T
and R
B
are directly
derived from V
DDA
. The video input is AC-coupled and
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
T
to +1.2
Volts while R
B
is grounded. The internal pull-up resistor,
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.
Grounding
The TMC1173A/1273 has separate analog and digital
circuits. To keep digital system noise from the A/D
converter, it is recommended that power supply voltages
(V
DDD
and V
DDA
) come from the same source, and that
ground connections (D
GND
and A
GND
) be made to the ana-
log ground plane. Power supply pins should be individually
decoupled at the pin. The digital circuitry that gets its input
from the TMC1173A/1273 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
likely to degrade performance. Overall system performance
is strongly influenced by the board layout. Capacitive cou-
pling 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
IN
, R
T
, R
B
, VR+, VR-)
as short as possible and as far as possible from all digital
signals. The TMC1173A/1273 should be located near
the board edge, close to the analog input connectors.
2.
The power plane for the TMC1173A/1273 should be
separate from that which supplies the rest of the digital
circuitry. A single power plane should be used for all of
the V
DD
pins. If the power supply for the TMC1173A/
1273 is the same as that of the system's digital circuitry,
power to the TMC1173A/1273 should be decoupled
with ferrite beads and 0.1
m
F capacitors to reduce noise.
3.
The ground plane should be solid, not cross-hatched.
Connections to the ground plane should have very short
leads.
4.
Decoupling capacitors should be applied liberally to
V
DD
pins. Remember that not all power supply pins are
created equal. They supply different circuits on the inte-
grated circuit, each of which generate varying amounts
and types of noise. For best results, use 0.1
m
F ceramic
capacitors. Lead lengths should be minimized. Ceramic
chip capacitors are the best choice.
5.
If the digital power supply has a dedicated power plane
layer, it should not be placed under the TMC1173A/
1273, the voltage reference, or the analog inputs. Capac-
itive coupling of digital power supply noise from this
layer to the TMC1173A/1273 and its related analog cir-
cuitry can have an adverse effect on performance.
6.
CONV should be handled carefully. Jitter and noise on
this clock may degrade performance. Terminate the
clock line carefully to eliminate overshoot and ringing.
Evaluation Board
An evaluation board is available that implements good inter-
face practices and provide a convenient testbed for develop-
ing system applications and circuit variations. An on-board
D/A converter is provided to reconstruct the digitized signal
and to evaluate converter performance.
Contact your sales representative for information.
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PDF描述 |
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| TMC1203KLC20 | Triple Video A/D Converter |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TMC1275M7C20 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Video A/D Conveter |
| TMC1275M7C30 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Video A/D Conveter |
| TMC1275M7C40 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Video A/D Conveter |
| TMC1275N2C20 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Video A/D Conveter |
| TMC1275N2C30 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Video A/D Conveter |
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