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参数资料
| 型号： | LTC2226IUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC 12BIT 25MSPS SAMPL 32-QFN |
| 标准包装： | 73 |
| 位数： | 12 |
| 采样率（每秒）： | 25M |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 90mW |
| 电压电源： | 单电源 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-QFN 裸露焊盘（5x5） |
| 包装： | 管件 |
| 输入数目和类型： | 1 个单端，双极; 1 个差分，双极 |
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LTC2228/LTC2227/LTC2226
16
222876fb
APPLICATIONS INFORMATION
CONVERTER OPERATION
As shown in Figure 1, the LTC2228/LTC2227/LTC2226
is a CMOS pipelined multi-step converter. The converter
has six pipelined ADC stages; a sampled analog input will
result in a digitized value ve cycles later (see the Timing
Diagram section). For optimal AC performance the analog
inputs should be driven differentially. For cost sensitive
applications, the analog inputs can be driven single-ended
with slightly worse harmonic distortion. The CLK input is
single-ended. The LTC2228/LTC2227/LTC2226 has two
phases of operation, determined by the state of the CLK
input pin.
Each pipelined stage shown in Figure 1 contains an ADC,
a reconstruction DAC and an interstage residue amplier.
In operation, the ADC quantizes the input to the stage and
the quantized value is subtracted from the input by the
DAC to produce a residue. The residue is amplied and
output by the residue amplier. Successive stages operate
out of phase so that when the odd stages are outputting
their residue, the even stages are acquiring that residue
and vice versa.
When CLK is low, the analog input is sampled differentially
directly onto the input sample-and-hold capacitors, inside
the “Input S/H” shown in the Block Diagram. At the instant
that CLK transitions from low to high, the sampled input is
held. While CLK is high, the held input voltage is buffered
by the S/H amplier which drives the rst pipelined ADC
stage. The rst stage acquires the output of the S/H dur-
ing this high phase of CLK. When CLK goes back low, the
rst stage produces its residue which is acquired by the
second stage. At the same time, the input S/H goes back to
acquiring the analog input. When CLK goes back high, the
second stage produces its residue which is acquired by the
third stage. An identical process is repeated for the third,
fourth and fth stages, resulting in a fth stage residue
that is sent to the sixth stage ADC for nal evaluation.
Each ADC stage following the rst has additional range to
accommodate ash and amplier offset errors. Results
from all of the ADC stages are digitally synchronized such
that the results can be properly combined in the correction
logic before being sent to the output buffer.
SAMPLE/HOLD OPERATION AND INPUT DRIVE
Sample/Hold Operation
Figure 2 shows an equivalent circuit for the LTC2228/
LTC2227/LTC2226 CMOS differential sample-and-hold.
The analog inputs are connected to the sampling capaci-
tors (CSAMPLE) through NMOS transistors. The capacitors
shown attached to each input (CPARASITIC) are the summa-
tion of all other capacitance associated with each input.
During the sample phase when CLK is low, the transistors
connect the analog inputs to the sampling capacitors and
they charge to and track the differential input voltage. When
CLK transitions from low to high, the sampled input voltage
is held on the sampling capacitors. During the hold phase
when CLK is high, the sampling capacitors are disconnected
from the input and the held voltage is passed to the ADC
core for processing. As CLK transitions from high to low,
the inputs are reconnected to the sampling capacitors to
acquire a new sample. Since the sampling capacitors still
hold the previous sample, a charging glitch proportional to
the change in voltage between samples will be seen at this
time. If the change between the last sample and the new
sample is small, the charging glitch seen at the input will
be small. If the input change is large, such as the change
seen with input frequencies near Nyquist, then a larger
charging glitch will be seen.
VDD
15Ω
CPARASITIC
1pF
CPARASITIC
1pF
CSAMPLE
4pF
CSAMPLE
4pF
LTC2228/27/26
AIN
+
AIN
–
CLK
222876 F02
Figure 2. Equivalent Input Circuit
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相关代理商/技术参数 |
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| LTC2226IUH-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:12-Bit, 65/40/25Msps Low Power 3V ADCs |
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| LTC2226LX | 制造商:LINER 制造商全称:Linear Technology 功能描述:12-Bit, 25Msps 125°C ADC in LQFP |
| LTC2227 | 制造商:LINER 制造商全称:Linear Technology 功能描述:14-Bit, 80Msps Low Power 3V ADC |
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