參數(shù)資料
型號： ADS8327IB
英文描述： LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
中文描述： 低功耗，16位，500千赫，單/雙單極性輸入，模擬到數(shù)字串行接口變換器
文件頁數(shù)： 21/40頁
文件大?。?/td> 2759K
代理商： ADS8327IB
www.ti.com
ANALOG INPUT
When the converter enters hold mode, the voltage difference between the +IN and -IN inputs is captured on the
internal capacitor array. The voltage on the -IN input is limited between AGND - 0.2 V and AGND + 0.2 V,
allowing the input to reject small signals which are common to both the +IN and -IN inputs. The +IN input has a
range of -0.2 V to V
ref
+ 0.2 V. The input span (+IN - (-IN)) is limited to 0 V to V
ref
.
The (peak) input current through the analog inputs depends upon a number of factors: sample rate, input
voltage, and source impedance. The current into the ADS8327/28 charges the internal capacitor array during the
sample period. After this capacitance has been fully charged, there is no further input current. The source of the
analog input voltage must be able to charge the input capacitance (45 pF) to a 16-bit settling level within the
minimum acquisition time (238 ns). When the converter goes into hold mode, the input impedance is greater
than 1 G
.
Care must be taken regarding the absolute analog input voltage. To maintain linearity of the converter, the +IN
and -IN inputs and the span (+IN - (-IN)) should be within the limits specified. Outside of these ranges, converter
linearity may not meet specifications. To minimize noise, low bandwidth input signals with low-pass filters should
be used. Care should be taken to ensure that the output impedance of the sources driving the +IN and -IN
inputs are matched. If this is not observed, the two inputs could have different settling times. This may result in
an offset error, gain error, and linearity error which change with temperature and input voltage.
Device in Hold Mode
AGND
150
+IN
IN
AGND
+VA
150
4 pF
4 pF
40 pF
40 pF
Driver Amplifier Choice
The analog input to the converter needs to be driven with a low noise, op-amp like the THS4031 or OPA356. An
RC filter is recommended at the input pins to low-pass filter the noise from the source. Two resistors of 20
and
a capacitor of 470 pF is recommended. The input to the converter is a unipolar input voltage in the range 0 V to
V
ref
. The minimum -3dB bandwidth of the driving operational amplifier can be calculated to:
Bipolar to Unipolar Driver
In systems where the input is bipolar, the THS4031 can be used in the inverting configuration with an additional
DC bias applied to its + input so as to keep the input to the ADS8327/28 within its rated operating voltage range.
This configuration is also recommended when the ADS8327/28 is used in signal processing applications where
good SNR and THD performance is required. The DC bias can be derived from the REF3225 or the REF3240
reference voltage ICs. The input configuration shown in
Figure 53
is capable of delivering better than 91-dB
SNR and -96-dB THD at an input frequency of 10 kHz. In case bandpass filters are used to filter the input, care
should be taken to ensure that the signal swing at the input of the bandpass filter is small so as to keep the
ADS8327
ADS8328
SLAS415A–APRIL 2006–REVISED MAY 2006
THEORY OF OPERATION (continued)
Figure 51. Input Equivalent Circuit
f
3db
= (ln(2) ×(n+1))/(2
π
× t
ACQ
)
where
n
is equal to 16, the resolution of the ADC (in the case of the ADS8327/28). When t
ACQ
= 238 ns
(minimum acquisition time), the minimum bandwidth of the driving amplifier is 7.9 MHz. The bandwidth can be
relaxed if the acquisition time is increased by the application. The OPA365, OPA827, or THS4031 from Texas
Instruments are recommended. The THS4031 used in the source follower configuration to drive the converter is
shown in the typical input drive configuration,
Figure 52
.
21
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相關(guān)PDF資料
PDF描述
ADS8327IBPW LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
ADS8327IBPWR LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
ADS8327IPW LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
ADS8327IPWR LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
ADS8328I LOW POWER, 16-BIT, 500-kHz, SINGLE/DUAL UNIPOLAR INPUT, ANALOG-TO-DIGITAL CONVERTERS WITH SERIAL INTERFACE
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ADS8327IBPW 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2.7-5.5V 16-Bit 500KSPS Serial 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
ADS8327IBPWG4 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2.7-5.5V 16-Bit 500KSPS Serial 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
ADS8327IBPWR 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2.7-5.5V 16-Bit 500KSPS Serial 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
ADS8327IBPWRG4 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2.7-5.5V 16-Bit 500KSPS Serial 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
ADS8327IBRSAR 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2.7V-5.5V 16B 500 KSPS Ser 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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