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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： | 8/11页 |
| 文件大小： | 97K |
| 代理商： | SPT7855SCN |
SPT
6
5/18/98
SPT7855
TYPICAL INTERFACE CIRCUIT
Very few external components are required to achieve the
stated device performance. Figure 1 shows the typical inter-
face requirements when using the SPT7855 in normal circuit
operation. The following sections provide descriptions of the
major functions and outline critical performance criteria to
consider for achieving the optimal device performance.
The high sample rate is achieved by using multiple SAR ADC
sections in parallel, each of which samples the input signal in
sequence. Each ADC uses 16 clock cycles to complete a
conversion. The clock cycles are allocated as follows:
Table II - Clock Cycles
Clock
Operation
1
Reference zero sampling
2
Auto-zero comparison
3
Auto-calibrate comparison
4
Input sample
5-15
11-bit SAR conversion
16
Data transfer
The 16 phase clock, which is derived from the input clock,
synchronizes these events. The timing signals for adjacent
ADC sections are shifted by one clock cycle so that the analog
input is sampled on every cycle of the input clock by exactly
one ADC section. After 16 clock periods, the timing cycle
repeats. The latency from analog input sample to the corre-
sponding digital output is 12 clock cycles.
Since only 16 comparators are used, a huge power savings
is realized.
The auto-zero operation is done using a closed loop
system that uses multiple samples of the comparator's
response to a reference zero.
The auto-calibrate operation, which calibrates the gain of
the MSB reference and the LSB reference, is also done with
a closed loop system. Multiple samples of the gain error are
integrated to produce a calibration voltage for each ADC
section.
Capacitive displacement currents, which can induce sam-
pling error, are minimized since only one comparator
samples the input during a clock cycle.
The total input capacitance is very low since sections of the
converter which are not sampling the signal are isolated
from the input by transmission gates.
VOLTAGE REFERENCE
The SPT7855 requires the use of a single external voltage
reference for driving the high side of the reference ladder. It
must be within the range of 3 V to 5 V. The lower side of the
ladder is typically tied to AGND (0.0 V), but can be run up to
2.0 V with a second reference. The analog input voltage
range will track the total voltage difference measured be-
tween the ladder sense lines, VRHS and VRLS.
Force and sense taps are provided to ensure accurate and
stable setting of the upper and lower ladder sense line
voltages across part-to-part and temperature variations. By
using the configuration shown in figure 2, offset and gain
errors of less than
±2 LSB can be obtained.
Figure 1 - Typical Interface Circuit
POWER SUPPLIES AND GROUNDING
SPT suggests that both the digital and the analog supply
voltages on the SPT7855 be derived from a single analog
supply as shown in figure 1. A separate digital supply should
be used for all interface circuitry. SPT suggests using this
power supply configuration to prevent a possible latch-up
condition on power up.
OPERATING DESCRIPTION
The general architecture for the CMOS ADC is shown in the
block diagram. The design contains 16 identical successive
approximation ADC sections, all operating in parallel, a 16-
phase clock generator, an 11-bit 16:1 digital output multi-
plexer, correction logic, and a voltage reference generator
which provides common reference levels for each ADC
section.
VRHF
VRLS
VRLF
VRHS
VIN
CLK
VCAL
DAV
D10
D0
EN
AVDD
AGND
DGND* DVDD
Ref In
(+4 V)
VIN
CLK IN
Enable/Tri-State
(Enable = Active Low)
Interfacing
Logics
+D5
SPT7855
DGND
+
10 F
+5 V
Digital
+5 V
Digital
RTN
+D5
FB3
NOTES: 1) FB3 is to be located as closely to the device as possible.
2) There should be no additional connections to the right of FB1 and FB2.
3) All capacitors are 0.1 F surface-mount unless otherwise specified.
4) FB1, FB2 and FB3 are 10 H inductors or ferrite beads.
FB1
FB2
+A5
AGND
+
10 F
+5 V
Analog
+5 V
Analog
RTN
+A5
*To reduce the possibility of latch-up, avoid
connecting the DGND pins of the ADC to the
digital ground of the system.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| SPT7855SCTX | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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