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參數(shù)資料
| 型號(hào)： | ADS825E |
| 英文描述： | 10-Bit, 40MHz Sampling ANALOG-TO-DIGITAL CONVERTERS |
| 中文描述： | 10位，40MHz的采樣模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 11/12頁(yè) |
| 文件大?。?/td> | 199K |
| 代理商： | ADS825E |
11
ADS822, ADS825
the resistive reference ladder. The bandgap reference circuit
includes logic functions that allows setting the analog input
swing of the ADS822 and ADS825 to either a 1Vp-p or
2Vp-p full-scale range simply by tying the RSEL pin to a
Low or High potential, respectively. While operating the
ADS822 in the external reference mode, the buffer amplifi-
ers for the REFT and REFB are disconnected from the
reference ladder.
As shown, the ADS822 and ADS825 have internal 50k
pull-up resistors at the range select pin (RSEL) and refer-
ence select pin (INT/EXT). Leaving these pins open config-
ures the ADS822 and ADS825 for a 2Vp-p input range and
external reference operation. Setting the ADS822 and
ADS825 up for internal reference mode requires bringing
the INT/EXT pin Low.
The reference buffers can be utilized to supply up to 1mA
(sink and source) to external circuitry. The resistor ladders
of the ADS822 and ADS825 are divided into several seg-
ments and have two additional nodes, ByT and ByB, which
are brought out for external bypassing only (see Figure 6).
To ensure proper operation with any reference configura-
tions, it is necessary to provide solid bypassing at all refer-
ence pins in order to keep the clock feedthrough to a
minimum. All bypassing capacitors should be located as
close to their respective pins as possible.
The common-mode voltage available at the CM pin may be
used as a bias voltage to provide the appropriate offset for
the driving circuitry. However, care must be taken not to
appreciably load this node, which is not buffered and has a
high impedance. An alternative way of generating a com-
mon-mode voltage is given in Figure 7. Here, two external
precision resistors (tolerance 1% or better) are located
between the top and bottom reference pins. The common-
mode voltage, CMV, will appear at the midpoint.
EXTERNAL REFERENCE OPERATION
For even more design flexibility, the internal reference can
be disabled and an external reference voltage be used. The
utilization of an external reference may be considered for
applications requiring higher accuracy, improved tempera-
ture performance, or a wide adjustment range of the
converter’s full-scale range. Especially in multichannel
applications, the use of a common external reference has the
benefit of obtaining better matching of the full-scale range
between converters.
The external references can vary as long as the value of the
external top reference REFT
EXT
stays within the range of
(V
S
– 1.25V) and (REFB + 0.8V), and the external bottom
reference REFB
EXT
stays within 1.25V and (REFT – 0.8V)
(See Figure 8).
DIGITAL INPUTS AND OUTPUTS
Clock Input Requirements
Clock jitter is critical to the SNR performance of high-speed,
high-resolution A/D converters. Clock jitter leads to aperture
jitter (t
A
), which adds noise to the signal being converted. The
ADS822 and ADS825 samples the input signal on the rising
edge of the CLK input. Therefore, this edge should have the
lowest possible jitter. The jitter noise contribution to total
FIGURE 8. Configuration Example for External Reference Operation.
FIGURE 7. Alternative Circuit to Generate CM Voltage.
REFT
+3.5V
ADS822
ADS825
CMV
+2.5V
REFB
+1.5V
R
1
1.6k
R
2
1.6k
0.1
μ
F
0.1
μ
F
ADS822
ADS825
IN
IN
INT/EXT
REFT
ByT
GND
ByB
REFB
4 x 0.1
μ
F || 2.2
μ
F
External Top Reference
REFT = REFB +0.8V to +3.75V
+VS
B
A
RSEL
GND
+5V
External Bottom Reference
REFB = REFT –0.8V to +1.25V
V
IN
A - Short for 1Vp-p Input Range
B - Short for 2Vp-p Input Range (Default)
CMV
+2.5V
DC
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS825E | 制造商:Texas Instruments 功能描述:Analog-Digital Converter IC Number of Bi |
| ADS825E/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10Bit 40MSPS SE/Diff Inp Int/Ext Ref 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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 |
| ADS825E/1KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10Bit 40MSPS SE/Diff Inp Int/Ext Ref 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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 |
| ADS825EG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10Bit 40MSPS SE/Diff Inp Int/Ext Ref 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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 |
| ADS826 | 制造商:BB 制造商全稱(chēng):BB 功能描述:10-Bit. 60MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
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