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| 型号： | DDC112U/1K |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | ADC |
| 英文描述： | 2-CH 20-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PDSO28 |
| 封装： | GREEN, PLASTIC, SOIC-28 |
| 文件页数： | 34/34页 |
| 文件大小： | 776K |
| 代理商： | DDC112U/1K |
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DDC112
9
SBAS085B
www.ti.com
DEVICE OPERATION
Basic Integration Cycle
The fundamental topology of the front end of the DDC112 is
a classical analog integrator, as shown in Figure 3. In this
diagram, only Input 1 is shown. This representation of the
input stage consists of an operational amplifier, a selectable
feedback capacitor network (CF), and several switches that
implement the integration cycle. The timing relationships of
all of the switches shown in Figure 3 are illustrated in
Figure 4. Figure 4 is used to conceptualize the operation of
the integrator input stage of the DDC112 and should not be
used as an exact timing tool for design. Block diagrams of
the reset, integrate, converter, and wait states of the inte-
grator section of the DDC112 are shown in Figure 5. This
internal switching network is controlled externally with the
convert command (CONV), range selection pins (RANGE0-
RANGE2), and the system clock (CLK). For the best noise
performance, CONV must be synchronized with the rising
edge of CLK. It is recommended CONV toggle within
±10ns
of the rising edge of CLK.
The noninverting inputs of the integrators are internally
referenced to ground. Consequently, the DDC112 analog
ground should be as clean as possible. The range switches,
along with the internal and external capacitors (CF) are
shown in parallel between the inverting input and output of
the operational amplifier. Table I shows the value of the
integration capacitor (CF) for each range. At the beginning of
a conversion, the switches SA/D, SINTA, SINTB, SREF1, SREF2,
and SRESET are set (see Figure 4).
At the completion of an A/D conversion, the charge on the
integration capacitor (CF) is reset with SREF1 and
CF
INPUT RANGE
RANGE2
RANGE1
RANGE0
(pF, typ)
(pC, typ)
0
External
Up to 1000
12.5 to 250
0
1
12.5
–0.2 to 50
01
0
25
–0.4 to 100
0
1
37.5
–0.6 to 150
10
0
50
–0.8 to 200
1
0
1
62.5
–0.1 to 250
11
0
75
–1.2 to 300
1
87.5
–1.4 to 350
TABLE I. Range Selection of the DDC112.
FIGURE 3. Basic Integrator Configuration for Input 1 Shown with a 250pC (CF = 62.5pF) Input Range.
SRESET (see Figures 4 and 5a). This is done during the reset
time. In this manner, the selected capacitor is charged to the
reference voltage, VREF. Once the integration capacitor is
charged, SREF1, and SRESET are switched so that VREF is no
longer connected to the amplifier circuit while it waits to begin
integrating (see Figure 5b). With the rising edge on CONV,
SINTA closes which begins the integration of Channel A. This
puts the integrator stage into its integrate mode (see
Figure 5c).
Charge from the input signal is collected on the integration
capacitor causing the voltage output of the amplifier to
decrease. A falling edge CONV stops the integration by
switching the input signal from side A to side B (SINTA and
SINTB). Prior to the falling edge of CONV, the signal on side
B was converted by the A/D converter and reset during the
time that side A was integrating. With the falling edge of
CONV, side B starts integrating the input signal. Now the
output voltage of side A’s operational amplifier is presented
to the input of the
Σ A/D converter (see Figure 5d).
50pF
CAP1A
25pF
12.5pF
V
REF
RANGE2
RANGE1
RANGE0
To Converter
S
RESET
S
REF2
S
A/D1A
S
INTA
S
REF1
S
INTB
IN1
ESD
Protection
Diode
Input
Current
Integrator A
Integrator B (same as A)
Photodiode
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相关代理商/技术参数 |
参数描述 |
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| DDC112UG4 | 功能描述:模数转换器 - ADC Dual Current Input 20-Bit 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 |
| DDC112UK | 功能描述:模数转换器 - ADC Dual Current Input 20-Bit 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 |
| DDC112UK | 制造商:Texas Instruments 功能描述:DUAL CURRENT INPUT 20 BIT ANALOG/DIGITAL |
| DDC112UK | 制造商:Texas Instruments 功能描述:20BIT ADC DUAL SMD SOIC28 112 |
| DDC112UK/1K | 功能描述:模数转换器 - ADC Dual Current Input 20-Bit 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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