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參數(shù)資料
| 型號： | CLC949ACQ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | ADC |
| 英文描述： | Very Low-Power, 12-Bit, 20MSPS Monolithic A/D Convertter |
| 中文描述： | 1-CH 12-BIT PROPRIETARY METHOD ADC, PARALLEL ACCESS, PQCC44 |
| 封裝： | PLASTIC, LCC-44 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大小： | 737K |
| 代理商： | CLC949ACQ |
7
http://www.national.com
with a frequency of 1/2 the sample rate. The bias current
was then turned up until the SNR was better than 65dB
and the SFDR exceeded 72dB. The axis on the left
shows the power that was dissipated by the device as a
function of speed, whereas the other curve uses the axis
on the right to show the resistor value required to obtain
this bias.
Figure 6: Power Dissipation & Programming
Resistor vs. Sample Rate
Dynamic Power Down
In systems where you do not use the A/D converter con-
tinually, and low power consumption is a key require-
ment, the power to the CLC949 can be turned down while
it is not being used. This is done through the use of the
BIASC pin, and a programming resistor to the power
supply. When the potential on this resistor is brought low,
the part goes into a sleep mode which saves power. This
can be accomplished by connecting the bias setting
resistor to a CMOS gate as shown in Figure 7. In sleep
mode the CLC949 will draw approximately 8mA, or
40mW on a 5V supply.
Figure 7: Dynamic Power Savings
PCB Layout
The keys to a successful CLC949 layout are
a substantial low-impedance ground plane, short
connections in and out of the data converter, and proper
power supply decoupling. The use of a socket for the
final design is not recommended but if one must be used
during debug or prototyping, then Comlinear recommends
the McKenzie #PLCC-44P-T-SMT socket which has low
parasitic impedances. The traces from the clock source
to the CLC949 should be as short as possible, if forced
to put the clock driver more than a couple of
centimeters away from the CLC949, then add a buffer for
the clock right next to the CLC949.
There is an evaluation board available for the CLC949
(E949PCASM) This board can be used to quickly
evaluate the performance of the CLC949 data converter.
Use of this evaluation board as a model for your PCB lay-
out is recommended. The schematic for this evaluation
board is shown in Figure 8 on the following page. The
board layout for the E949PCASM is shown in the
E949PCASM datasheet.
Power Supplies, Grounding and Bypassing
To obtain the best possible performance from high speed
devices, you must pay close attention to power supplies,
bypassing and grounding. This applies not only to the
A/D converter itself but to the entire system.
The recommended supply decoupling scheme for the
CLC949 includes:
One 0.01 to 0.033
μ
F capacitor between each
power pin and GND.
One 6.8 to 10
μ
F capacitor per board, placed no
more than a few inches from the A/D connected
between V
DD
and GND.
One 0.1
μ
F capacitor from each of the reference
inputs (V
REFP
, V
REFN
, V
REFPC
, V
REFNC
) to GND.
If the board has supplies that include excessive
digital switching noise, then ferrite beads in series
with the power feed to the A/D should also be
included.
Proper bypassing of all other integrated circuits
on the board, especially digital logic I.C.s.
CLC949
CMOS Inverter
V
DD
BC0
BIASC
BC1
Sleep
10k
*See Figure 6 above.
R
p
*
Power Dissipation & Programming
Resistor vs. Sample Rate
P
R
p
)
Sample Rate (MSPS)
200
150
0
5
10
50
0
100
Power
Resistor
20
50
40
20
0
30
15
Ordering Information
Model
Temperature Range
Description
CLC949ACQ
CLC949AJQ
0
C to +70
C
-40
C to +85
C
44-pin PLCC
44-pin PLCC
Package Thermal Resistance
Package
q
JC
q
JA
44-pin PLCC
10
°
C/W
35
°
C/W
Power Requirements
Typ
65
220
400
Units
mW
mW
mW
V
cc
= +5V, 5MSPS, Low Bias
V
cc
= +5V, 20MSPS, Med Bias
V
cc
= +5V, 30MSPS, High Bias
相關(guān)PDF資料 |
PDF描述 |
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| CLC949AJQ | Very Low-Power, 12-Bit, 20MSPS Monolithic A/D Convertter |
| CLC952PCASM | CLC949ACQ |
| CLC952 | CLC949ACQ |
| CLC952ACMSA | CLC949ACQ |
| CLC952AJMSA | CLC949ACQ |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CLC949AJQ | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Texas Instruments 功能描述: |
| CLC952 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:CLC949ACQ |
| CLC952 WAF | 制造商:Texas Instruments 功能描述: |
| CLC952ACMSA | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| CLC952AJMSA | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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