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參數(shù)資料
| 型號： | SPT7855SCN |
| 廠商： | SIGNAL PROCESSING TECHNOLOGIES |
| 元件分類： | ADC |
| 英文描述： | 1-CH 10-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PDIP28 |
| 封裝： | PLASTIC, DIP-28 |
| 文件頁數(shù)： | 9/11頁 |
| 文件大小： | 97K |
| 代理商： | SPT7855SCN |
SPT
7
5/18/98
SPT7855
Figure 2 - Ladder Force/Sense Circuit
Figure 3 - Reference Ladder
AGND
VRHF
VRHS
VRLS
VRLF
VIN
1
2
3
5
6
7
+
-
+
-
All capacitors are 0.01 F
4
N/C
R/2
R
R/2
R=30
(typ)
All capacitors are 0.01 F
VRLF (AGND)
0.0 V
VRLS
(0.075 V)
VRHS
(+3.91 V)
90 mV
75 mV
+4.0 V
External
Reference
In cases where wider variations in offset and gain can be
tolerated, VRef can be tied directly to VRHF and AGND can be
tied directly to VRLF as shown in figure 3. Decouple force and
sense lines to AGND with a .01
F capacitor (chip cap
preferred) to minimize high-frequency noise injection. If this
simplified configuration is used, the following considerations
should be taken into account:
The reference ladder circuit shown in figure 3 is a simplified
representation of the actual reference ladder with force and
sense taps shown. Due to the actual internal structure of the
ladder, the voltage drop from VRHF to VRHS is not equivalent
to the voltage drop from VRLF to VRLS.
Typically, the top side voltage drop for VRHF to VRHS will
equal:
VRHF - VRHS = 2.25 % of (VRHF - VRLF) (typical),
and the bottom side voltage drop for VRLS to VRLF will equal:
VRLS - VRLF = 1.9 % of (VRHF - VRLF) (typical).
Figure 3 shows an example of expected voltage drops for a
specific case. Vref of 4.0 V is applied to VRHF and VRLF is tied
to AGND. A 90 mV drop is seen at VRHS (= 3.91 V) and a
75 mV increase is seen at VRLS (= 0.075 V).
ANALOG INPUT
VIN is the analog input. The input voltage range is from VRLS
to VRHS (typically 4.0 V) and will scale proportionally with
respect to the voltage reference. (See voltage reference
section.)
The drive requirements for the analog inputs are very minimal
when compared to most other converters due to the SPT7855's
extremely low input capacitance of only 5 pF and very high
input resistance of 50 k
.
The analog input should be protected through a series
resistor and diode clamping circuit as shown in figure 4.
CALIBRATION
The SPT7855 uses an auto calibration scheme to ensure 10-
bit accuracy over time and temperature. Gain and offset
errors are continually adjusted to 10-bit accuracy during
device operation. This process is completely transparent to
the user.
Upon power-up, the SPT7855 begins its calibration algo-
rithm. In order to achieve the calibration accuracy required,
the offset and gain adjustment step size is a fraction of a 10-
bit LSB. Since the calibration algorithm is an oversampling
process, a minimum of 10,000 clock cycles are required. This
results in a minimum calibration time upon power-up of
400
sec (for a 25 MHz clock). Once calibrated, the SPT7855
remains calibrated over time and temperature.
Since the calibration cycles are initiated on the rising edge of
the clock, the clock must be continuously applied for the
SPT7855 to remain in calibration.
INPUT PROTECTION
All I/O pads are protected with an on-chip protection circuit
shown in figure 5. This circuit provides ESD robustness to
3.5 kV and prevents latch-up under severe discharge condi-
tions without degrading analog transition times.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SPT7855SCS | 功能描述:視頻模擬/數(shù)字化轉(zhuǎn)換器集成電路 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 輸入信號類型:Differential 轉(zhuǎn)換器數(shù)量:1 ADC 輸入端數(shù)量:4 轉(zhuǎn)換速率:3 Gbps 分辨率:8 bit 結(jié)構(gòu): 輸入電壓:3.3 V 接口類型:SPI 信噪比: 電壓參考: 電源電壓-最大:3.45 V 電源電壓-最小:3.15 V 最大功率耗散: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:TCSP-48 封裝:Reel |
| SPT7855SCS_Q | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10BIT 40MSPS SaR 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 |
| SPT7855SCT | 功能描述:視頻模擬/數(shù)字化轉(zhuǎn)換器集成電路 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 輸入信號類型:Differential 轉(zhuǎn)換器數(shù)量:1 ADC 輸入端數(shù)量:4 轉(zhuǎn)換速率:3 Gbps 分辨率:8 bit 結(jié)構(gòu): 輸入電壓:3.3 V 接口類型:SPI 信噪比: 電壓參考: 電源電壓-最大:3.45 V 電源電壓-最小:3.15 V 最大功率耗散: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:TCSP-48 封裝:Reel |
| SPT7855SCT_Q | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10BIT 40MSPS SaR 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 |
| SPT7855SCTX | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
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