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参数资料
| 型号： | SPT7855SCN |
| 厂商： | SIGNAL PROCESSING TECHNOLOGIES |
| 元件分类： | ADC |
| 英文描述： | 1-CH 10-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PDIP28 |
| 封装： | PLASTIC, DIP-28 |
| 文件页数： | 9/11页 |
| 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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| SPT7855SCS | 功能描述:视频模拟/数字化转换器集成电路 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 输入信号类型:Differential 转换器数量:1 ADC 输入端数量:4 转换速率:3 Gbps 分辨率:8 bit 结构: 输入电压:3.3 V 接口类型:SPI 信噪比: 电压参考: 电源电压-最大:3.45 V 电源电压-最小:3.15 V 最大功率耗散: 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:TCSP-48 封装:Reel |
| SPT7855SCS_Q | 功能描述:模数转换器 - ADC 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| SPT7855SCT | 功能描述:视频模拟/数字化转换器集成电路 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 输入信号类型:Differential 转换器数量:1 ADC 输入端数量:4 转换速率:3 Gbps 分辨率:8 bit 结构: 输入电压:3.3 V 接口类型:SPI 信噪比: 电压参考: 电源电压-最大:3.45 V 电源电压-最小:3.15 V 最大功率耗散: 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:TCSP-48 封装:Reel |
| SPT7855SCT_Q | 功能描述:模数转换器 - ADC 10BIT 40MSPS SaR aDC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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