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| 型号： | DC1783A-E |
| 厂商： | Linear Technology |
| 文件页数： | 3/26页 |
| 文件大小： | 0K |
| 描述： | BOARD SAR ADC LTC2379-18 |
| 软件下载： | QuikEval II System |
| 设计资源： | DC1783A Design Files DC1783A Schematic |
| 标准包装： | 1 |
| 系列： | QuikEval™ |
| ADC 的数量： | 1 |
| 位数： | 18 |
| 采样率（每秒）： | 1.6M |
| 数据接口： | 串行，SPI? |
| 输入范围： | ±VREF |
| 在以下条件下的电源（标准）： | 18mW @ 1.6MSPS |
| 工作温度： | 0°C ~ 70°C |
| 已用 IC / 零件： | LTC2379-18 |
| 已供物品： | 板 |
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LTC2379-18
11
237918fa
APPLICATIONS INFORMATION
INPUT DRIVE CIRCUITS
A low impedance source can directly drive the high im-
pedance inputs of the LTC2379-18 without gain error. A
high impedance source should be buffered to minimize
settling time during acquisition and to optimize the dis-
tortion performance of the ADC. Minimizing settling time
is important even for DC inputs, because the ADC inputs
draw a current spike when entering acquisition.
For best performance, a buffer amplifier should be used
to drive the analog inputs of the LTC2379-18. The ampli-
fier provides low output impedance, which produces fast
settling of the analog signal during the acquisition phase.
It also provides isolation between the signal source and
the current spike the ADC inputs draw.
Input Filtering
The noise and distortion of the buffer amplifier and signal
source must be considered since they add to the ADC noise
and distortion. Noisy input signals should be filtered prior
to the buffer amplifier input with an appropriate filter to
minimize noise. The simple 1-pole RC lowpass filter (LPF1)
shown in Figure 4 is sufficient for many applications.
20Ω
3300pF
6600pF
20Ω
500Ω
LPF2
LPF1
BW = 800kHz
BW = 48kHz
SINGLE-ENDED-
TO-DIFFERENTIAL
DRIVER
SINGLE-ENDED-
INPUT SIGNAL
LTC2379-18
IN+
IN–
237918 F04
3300pF
High quality capacitors and resistors should be used in the
RC filters since these components can add distortion. NPO
and silver mica type dielectric capacitors have excellent
linearity. Carbon surface mount resistors can generate
distortion from self heating and from damage that may
occur during soldering. Metal film surface mount resistors
are much less susceptible to both problems.
Single-Ended-to-Differential Conversion
For single-ended input signals, a single-ended to differential
conversion circuit must be used to produce a differential
signal at the inputs of the LTC2379-18. The LT6350 ADC
driver is recommended for performing single-ended-to-
differential conversions. The LT6350 is flexible and may
be configured to convert single-ended signals of various
amplitudes to the ±5V differential input range of the
LTC2379-18. The LT6350 is also available in H-grade to
complement the extended temperature operation of the
LTC2379-18 up to 125°C.
Figure 5a shows the LT6350 being used to convert a 0V
to 5V single-ended input signal. In this case, the first
amplifier is configured as a unity gain buffer and the single-
ended input signal directly drives the high-impedance
input of the amplifier. As shown in the FFT of Figure 5b,
the LT6350 drives the LTC2379-18 to near full datasheet
performance.
The LT6350 can also be used to buffer and convert large
true bipolar signals which swing below ground to the
±5V differential input range of the LTC2379-18 in order
to maximize the signal swing that can be digitized. Fig-
ure6a shows the LT6350 being used to convert a ±10V
true bipolar signal for use by the LTC2379-18. In this
case, the first amplifier in the LT6350 is configured as
an inverting amplifier stage, which acts to attenuate and
level shift the input signal to the 0V to 5V input range of
the LTC2379-18. In the inverting amplifier configuration,
the single-ended input signal source no longer directly
drives a high impedance input of the first amplifier. The
input impedance is instead set by resistor RIN. RIN must
be chosen carefully based on the source impedance of the
signal source. Higher values of RIN tend to degrade both
the noise and distortion of the LT6350 and LTC2379-18
as a system.
Figure 4. Input Signal Chain
Another filter network consisting of LPF2 should be used
between the buffer and ADC input to both minimize the
noise contribution of the buffer and to help minimize distur-
bances reflected into the buffer from sampling transients.
Long RC time constants at the analog inputs will slow
down the settling of the analog inputs. Therefore, LPF2
requires a wider bandwidth than LPF1. A buffer amplifier
with a low noise density must be selected to minimize
degradation of the SNR.
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| DC1783A-F | 功能描述:BOARD SAR ADC LTC2378-18 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:QuikEval™ 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
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| DC1785A | 制造商:Linear Technology 功能描述:EVAL BOARD, LTC2991 TEMP, VOLTAGE, CURRE |
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