参数资料
| 型号： | AD7863AR-2 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 2/24页 |
| 文件大小： | 0K |
| 描述： | IC ADC 14BIT DUAL 2CH 28-SOIC |
| 产品变化通告： | Product Discontinuance 27/Oct/2011 |
| 标准包装： | 27 |
| 位数： | 14 |
| 采样率（每秒）： | 175k |
| 数据接口： | 并联 |
| 转换器数目： | 2 |
| 功率耗散（最大）： | 94.5mW |
| 电压电源： | 模拟和数字 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 28-SOIC W |
| 包装： | 管件 |
| 输入数目和类型： | 4 个单端，单极；4 个单端，双极 |
AD7863
Rev. B | Page 10 of 24
CIRCUIT DESCRIPTION
ANALOG INPUT SECTION
The AD7863 is offered as three part types: the AD7863-10,
which handles a ±10 V input voltage range, the AD7863-3,
which handles input voltage range ±2.5 V and the AD7863-2,
which handles a 0 V to 2.5 V input voltage range.
2.5V
REFERENCE
MUX
R2
R1
R3
TO INTERNAL
COMPARATOR
TRACK/
HOLD
VREF
VAX
AGND
AD7863-10/AD7863-3
2k
TO ADC
REFERENCE
CIRCUITRY
06
41
1-
0
05
Figure 5. AD7863-10/AD7863-3 Analog Input Structure
Figure 5 shows the analog input section for the AD7863-10 and
AD7863-3. The analog input range of the AD7863-10 is ±10 V
into an input resistance of typically 9 kΩ. The analog input
range of the AD7863-3 is ±2.5 V into an input resistance of
typically 3 kΩ. This input is benign, with no dynamic charging
currents because the resistor stage is followed by a high input
impedance stage of the track-and-hold amplifier. For the
AD7863-10, R1 = 8 kΩ, R2 = 2 kΩ and R3 = 2 kΩ. For the
AD7863-3, R1 = R2 = 2 kΩ and R3 is open circuit.
For the AD7863-10 and AD7863-3, the designed code
transitions occur on successive integer LSB values (that is, 1 LSB,
2 LSBs, 3 LSBs . . .). Output coding is twos complement binary
with 1 LSB = FS/16,384. The ideal input/output transfer
function for the AD7863-10 and AD7863-3 is shown in Table 5.
Table 5. Ideal Input/Output Code (AD7863-10/AD7863-3)
Analog Input1
Digital Output Code Transition
+FSR/2 1 LSB2
011 . . . 110 to 011 . . . 111
+FSR/2 2 LSBs
011 . . . 101 to 011 . . . 110
+FSR/2 3 LSBs
011 . . . 100 to 011 . . . 101
GND + 1 LSB
000 . . . 000 to 000 . . . 001
GND
111 . . . 111 to 000 . . . 000
GND 1 LSB
111 . . . 110 to 111 . . . 111
FSR/2 + 3 LSBs
100 . . . 010 to 100 . . . 011
FSR/2 + 2 LSBs
100 . . . 001 to 100 . . . 010
FSR/2 + 1 LSB
100 . . . 000 to 100 . . . 001
1FSR is full-scale range = 20 V (AD7863-10) and = 5 V (AD7863-3) with VREF = 2.5 V.
21 LSB = FSR/16,384 = 1.22 mV (AD7863-10) and 0.3 mV (AD7863-3) with
VREF = 2.5 V.
The analog input section for the AD7863-2 contains no biasing
resistors and the VAX/BX pin drives the input directly to the
multiplexer and track-and-hold amplifier circuitry. The analog
input range is 0 V to 2.5 V into a high impedance stage with an
input current of less than 100 nA. This input is benign, with no
dynamic charging currents. Once again, the designed code
transitions occur on successive integer LSB values. Output
coding is straight (natural) binary with 1 LSB = FS/16,384 =
2.5 V/16,384 = 0.15 mV. Table 6 shows the ideal input/output
transfer function for the AD7863-2.
Table 6. Ideal Input/Output Code (AD7863-2)
Analog Input1
Digital Output Code Transition
+FSR 1 LSB2
111 . . . 110 to 111 . . . 111
+FSR 2 LSB
111 . . . 101 to 111 . . . 110
+FSR 3 LSB
111 . . . 100 to 111 . . . 101
GND + 3 LSB
000 . . . 010 to 000 . . . 011
GND + 2 LSB
000 . . . 001 to 000 . . . 010
GND + 1 LSB
000 . . . 000 to 000 . . . 001
1FSR is full-scale range = 2.5 V for AD7863-2 with VREF = 2.5 V.
21 LSB = FSR/16,384 = 0.15 mV for AD7863-2 with VREF = 2.5 V.
OFFSET AND FULL-SCALE ADJUSTMENT
In most digital signal processing (DSP) applications, offset and
full-scale errors have little or no effect on system performance.
Offset error can always be eliminated in the analog domain by
ac coupling. Full-scale error effect is linear and does not cause
problems as long as the input signal is within the full dynamic
range of the ADC. Invariably, some applications require that the
input signal span the full analog input dynamic range. In such
applications, offset and full-scale error have to be adjusted to zero.
Figure 6 shows a typical circuit that can be used to adjust the
offset and full-scale errors on the AD7863 (VA1 on the
AD7863-10 version is shown for example purposes only).
Where adjustment is required, offset error must be adjusted
before full-scale error. This is achieved by trimming the offset
of the op amp driving the analog input of the AD7863 while the
input voltage is LSB below analog ground. The trim
procedure is as follows: apply a voltage of 0.61 mV ( LSB)
ADC output code flickers between 11 1111 1111 1111 and
00 0000 0000 0000.
R2
500
*ADDITIONAL PINS OMITTED FOR CLARITY.
VA1
AGND
AD7863*
R1
10k
R3
10k
R5
10k
R4
10k
V1
INPUT RANGE = ±10V
06
41
1-
0
06
Figure 6. Full-Scale Adjust Circuit
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| AD7863AR-2REEL | 制造商:Analog Devices 功能描述:ADC Dual SAR 175ksps 14-bit Parallel 28-Pin SOIC W T/R |
| AD7863AR-2REEL7 | 功能描述:IC ADC 14BIT DUAL 2CH 28-SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 位数:12 采样率（每秒）:3M 数据接口:- 转换器数目:- 功率耗散（最大）:- 电压电源:- 工作温度:- 安装类型:表面贴装 封装/外壳:SOT-23-6 供应商设备封装:SOT-23-6 包装:带卷 (TR) 输入数目和类型:- |
| AD7863AR-3 | 功能描述:IC ADC 14BIT DUAL 2CH 28-SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1 系列:- 位数:14 采样率（每秒）:83k 数据接口:串行，并联 转换器数目:1 功率耗散（最大）:95mW 电压电源:双 ± 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:28-DIP（0.600"，15.24mm） 供应商设备封装:28-PDIP 包装:管件 输入数目和类型:1 个单端，双极 |
| AD7863AR-3REEL | 功能描述:IC ADC 14BIT DUAL 2CH 28-SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1 系列:- 位数:14 采样率（每秒）:83k 数据接口:串行，并联 转换器数目:1 功率耗散（最大）:95mW 电压电源:双 ± 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:28-DIP（0.600"，15.24mm） 供应商设备封装:28-PDIP 包装:管件 输入数目和类型:1 个单端，双极 |
| AD7863AR-3REEL7 | 功能描述:IC ADC 14BIT DUAL 2CH 28-SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1 系列:- 位数:14 采样率（每秒）:83k 数据接口:串行，并联 转换器数目:1 功率耗散（最大）:95mW 电压电源:双 ± 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:28-DIP（0.600"，15.24mm） 供应商设备封装:28-PDIP 包装:管件 输入数目和类型:1 个单端，双极 |
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