參數(shù)資料
型號(hào)： ADS5421Y
英文描述： 14-Bit, 40MHz Sampling ANALOG-TO-DIGITAL CONVERTER
中文描述： 14位，40MHz的采樣模擬數(shù)字轉(zhuǎn)換器
文件頁(yè)數(shù)： 14/21頁(yè)
文件大?。?/td> 395K
代理商： ADS5421Y
ADS5421
SBAS237D
14
www.ti.com
FIGURE 9. Example for an External Reference Circuit Using a Dual, Single-Supply Op Amp.
R
3
R
4
R
1
R
2
+
+
2.2
μ
F
0.1
μ
F
0.1
μ
F
+
2.2
μ
F
0.1
μ
F
10
μ
F
REFT
REFB
ADS5421
1/2
OPA2234
1/2
OPA2234
4.7k
+5V
+5V
REF1004
+2.5V
DIGITAL INPUTS AND OUTPUTS
CLOCK INPUT
Unlike most ADCs, the ADS5421 contains internal clock
conditioning circuitry. This enables the converter to adapt to
a variety of application requirements and different clock
sources. With no input signal connected to either clock pin,
the threshold level is set to approximately +1.6V by the on-
chip resistive voltage divider, as shown in Figure 10. The
parallel combination of R
1
|| R
2
and R
3
|| R
4
sets the input
impedance of the clock inputs (CLK,
CLK
) to approximately
2.7k
single-ended, or 5.5k
differentially. The associated
ground referenced input capacitance is approximately 5pF
for each input. If a logic voltage other than the nominal +1.6V
is desired, the clock inputs can be externally driven to
establish an alternate threshold voltage.
Applying a single-ended clock signal will provide satisfactory
results in many applications. However, unbalanced high-speed
logic signals can introduce a high amount of disturbances,
such as ringing or ground bouncing. In addition, a high
amplitude can cause the clock signal to have unsymmetrical
rise-and-fall times, potentially affecting the converter distortion
performance. Proper termination practice and a clean PC
board layout will help to keep those effects to a minimum.
To take full advantage of the excellent distortion performance
of the ADS5421, it is recommended to drive the clock inputs
differentially. A differential clock improves the digital
feedthrough immunity and minimizes the effect of modulation
between the signal and the clock. Figure 12 illustrates a
simple method of converting a square wave clock from
single-ended to differential using an RF transformer. Small
surface-mount transformers are readily available from sev-
eral manufacturers (e.g., model ADT1-1 by Mini-Circuits). A
capacitor in series with the primary side may be inserted to
block any DC voltage present in the signal. The secondary
side connects directly to the two clock inputs of the converter
because the clock inputs are self-biased.
FIGURE 10. The Differential Clock Inputs are Internally Biased.
+5V
R
1
8.5k
R
2
4k
R
8.5k
R
4
4k
CLK
CLK
ADS5421
CLK
CLK
ADS5421
47nF
TTL/CMOS
Clock Source
(3V/5V)
FIGURE 11. Single-Ended TTL/CMOS Clock Source.
The ADS5421 can be interfaced to standard TTL or CMOS
logic and accepts 3V or 5V compliant logic levels. In this
case, the clock signal should be applied to the CLK input,
whereas the complementary clock input (
CLK
) should be
bypassed to ground by a low-inductance ceramic chip ca-
pacitor, as shown in Figure 11. Depending on the quality of
the signal, inserting a series, damping resistor can be benefi-
cial to reduce ringing. When digitizing at high sampling rates
the clock should have a 50% duty cycle (t
H
= t
L
) to maintain
good distortion performance.
FIGURE 12. Connecting a Ground-Referenced Clock Source
to the ADS5421 Using an RF Transformer.
CLK
CLK
ADS5421
0.1
μ
F
1:1
Square Wave
or Sine Wave
Clock Source
R
S
R
T
XFR
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ADS5421Y/R 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 14 Bit 40MSPS Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
ADS5421Y/RG4 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 14 Bit 40MSPS Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
ADS5421Y/T 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 14 Bit 40MSPS Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
ADS5421Y/TG4 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 14 Bit 40MSPS Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
ADS5422 制造商:TI 制造商全稱:Texas Instruments 功能描述:14-Bit, 62MSPS Sampling ANALOG-TO-DIGITAL CONVERTER
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