參數(shù)資料
型號(hào)： ADS5421T
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)： 13/21頁(yè)
文件大?。?/td> 395K
代理商： ADS5421T
ADS5421
SBAS237D
13
www.ti.com
DESIRED FULL-SCALE
RANGE (FSR)
(DIFFERENTIAL)
CONNECT
SEL1 (PIN 45) TO:
CONNECT
SEL2 (PIN 44) TO:
VOLTAGE AT V
REF
(PIN 46)
VOLTAGE AT REFT
(PIN 52)
VOLTAGE AT REFB
(PIN 50)
4Vp-p (+16dBm)
3Vp-p (+13dBm)
2Vp-p (+10dBm)
External Reference
GND
GND
V
REF
—
GND
+V
SA
GND
—
+2.0V
+1.5V
+1.0V
> +3.5V
+3.5V
+3.25V
+3.0V
+1.5V
+1.75V
+2.0V
+2.75V to +4.5V
+0.5V to +2.25V
TABLE I. Reference Pin Configurations and Corresponding Voltages on the Reference Pins.
FIGURE 8. Internal Reference Circuit of the ADS5421 and Recommended Bypass Scheme.
Range Select
and
Gain Amplifier
Top
Reference
Driver
Bottom
Reference
Driver
+1V
Bandgap
Reference
ADS5421
+
+
+
REFT
CM
REFB
2.2
μ
F
2.2
μ
F
2.2
μ
F
0.1
μ
F
0.1
μ
F
0.1
μ
F
0.1
μ
F
0.1
μ
F
REFBY
SEL1 SEL2
V
REF
500
500
45
61
46
44
52
51
50
REFERENCE
REFERENCE OPERATION
Integrated into the ADS5421 is a bandgap reference circuit,
including logic that provides a +1V, +1.5V, or +2V reference
output by selecting the corresponding pin-strap configura-
tion. Table I lists a complete overview of the possible refer-
ence options and pin configurations.
Figure 8 shows the basic model of the internal reference
circuit. The functional blocks are a 1V bandgap voltage
reference, a selectable gain amplifier, the drivers for the top
and bottom reference (REFT, REFB), and the resistive refer-
ence ladder. The ladder resistance measures approximately
1k
between the REFT and REFB pins. The ladder is split
into two equal segments establishing a common-mode volt-
age at the ladder midpoint, labeled CM. The ADS5421
requires solid bypassing for all reference pins to keep the
effects of clock feedthrough to a minimum and to achieve the
specified level of performance. Figure 8 shows the recom-
mended decoupling scheme. All 0.1
μ
F capacitors must be
located as close to the pins as possible. In addition, pins
REFT, CM, and REFB must be decoupled with tantalum
surface-mount capacitors (2.2
μ
F or 4.7
μ
F).
When operating the ADS5421 with the internal reference, the
effective full-scale input span for each of the inputs, IN and
IN
, is determined by the voltage at the V
REF
pin, given to:
(1)
Input Span (differential, each input) = V
REF
= (REFT – REFB) in Vp-p
The top and bottom reference outputs can be used to provide
up to 1mA of current (sink or source) to external circuits.
Degradation of the differential linearity (DNL) and, conse-
quently, the dynamic performance, of the ADS5421 may
occur if this limit is exceeded.
USING EXTERNAL REFERENCES
For even more design flexibility, the ADS5421 can be oper-
ated with external references. The utilization of an external
reference voltage may be considered for applications requir-
ing higher accuracy, improved temperature stability, or a
continuous adjustment of the converter full-scale range.
Especially in multichannel applications, the use of a common
external reference offers the benefit of improving the gain
matching between converters. Selection between internal or
external reference operation is controlled through the V
REF
pin. The internal reference will become disabled if the voltage
applied to the V
REF
pin exceeds +3.5V
DC
. Once selected, the
ADS5421 requires two reference voltages: a top reference
voltage applied to the REFT pin and a bottom reference
voltage applied to the REFB pin (see Table I). As illustrated
in Figure 9, a micropower reference (REF1004) and a dual,
single-supply amplifier (OPA2234) can be used to generate
a precision external reference. Note that the function of the
range select pins, SEL1 and SEL2, are disabled while the
converter is operating in external reference mode.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ADS5421Y 制造商:BB 制造商全稱:BB 功能描述:14-Bit, 40MHz Sampling ANALOG-TO-DIGITAL CONVERTER
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
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