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| 型号： | AD7703AR |
| 厂商： | Analog Devices Inc |
| 文件页数： | 16/16页 |
| 文件大小： | 0K |
| 描述： | IC ADC 20BIT LC2MOS 20-SOIC |
| 标准包装： | 1 |
| 位数： | 20 |
| 采样率（每秒）： | 4k |
| 数据接口： | 串行 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 37mW |
| 电压电源： | 模拟和数字，双 ± |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 20-SOIC W |
| 包装： | 管件 |
| 输入数目和类型： | 1 个单端，单极；1 个单端，双极 |
REV. E
AD7703
–9–
Table II. Resonator Loading Capacitors
Resonators
C1 (pF)
C2 (pF)
Ceramic
200 kHz
330
470
455 kHz
100
1.0 MHz
50
2.0 MHz
20
Crystal
2.000 MHz
30
3.579 MHz
20
4.096 MHz
None
The input sampling frequency, output data rate, filter character-
istics, and calibration time are all directly related to the master
clock frequency, fCLKIN, by the ratios given in the Specification
table under Dynamic Performance. Therefore, the first step in
system design with the AD7703 is to select a master clock fre-
quency suitable for the bandwidth and output data rate required
by the application.
ANALOG INPUT RANGES
The AD7703 performs conversion relative to an externally
supplied reference voltage that allows easy interfacing to ratio-
metric systems. In addition, either unipolar or bipolar input
voltage ranges may be selected using the BP/
UP input. With
BP/
UP tied low, the input range is unipolar and the span is
(VREF to VAGND), where VAGND is the voltage at the device AGND
pin. With BP/
UP tied high, the input range is bipolar and the
span is 2VREF. In the Bipolar mode, both positive and negative
full scale are directly determined by VREF. This offers superior
tracking of positive and negative full scale and better midscale
(bipolar zero) stability than bipolar schemes that simply scale
and offset the input range.
The digital output coding for the unipolar range is unipolar binary;
for the bipolar range it is offset binary. Bit weights for the Unipolar
and Bipolar modes are shown in Table I.
ACCURACY
S-D ADCs, like VFCs and other integrating ADCs, do not
contain any source of nonmonotonicity and inherently offer
no-missing-codes performance.
The AD7703 achieves excellent linearity by the use of high
quality, on-chip silicon dioxide capacitors, which have a very
low capacitance/voltage coefficient. The device also achieves low
input drift through the use of chopper-stabilized techniques in
its input stage. To ensure excellent performance over time and
temperature, the AD7703 uses digital calibration techniques
that minimize offset and gain error to typically ±4 LSB.
AUTOCALIBRATION
The AD7703 offers both self-calibration and system-calibration
facilities. For calibration to occur, the on-chip microcontroller
must record the modulator output for two different input condi-
tions. These are the zero-scale and full-scale points. In Unipolar
self-calibration mode, the zero-scale point is VAGND and the
full-scale point is VREF. With these readings, the microcontroller
can calculate the gain slope for the input to output transfer
function of the converter. In Unipolar mode, the slope factor is
determined by dividing the span between zero and full scale by
2
20. In Bipolar mode, it is determined by dividing the span by
2
19 since the inputs applied represent only half the total codes.
In both Unipolar and Bipolar modes, the slope factor is saved
and used to calculate the binary output code when an analog
input is applied to the device. Table IV gives the output code
size after calibration.
System calibration allows the AD7703 to compensate for system
gain and offset errors. A typical circuit where this might be used
is shown in Figure 12.
System calibration performs the same slope factor calculations
as self-calibration but uses voltage values presented by the system
to the AIN pin for the zero- and full-scale points. There are two
system calibration modes.
The first mode offers system level calibration for system offset
and system gain. This is a two step operation. The zero-scale
point must be presented to the converter first. It must be applied
to the converter before the calibration step is initiated and remain
stable until the step is complete. The
DRDY output from the
device will signal when the step is complete by going low. After
the zero-scale point is calibrated, the full-scale point is applied
and the second calibration step is initiated. Again, the voltage
must remain stable throughout the calibration step.
The two step calibration mode offers another feature. After the
sequence has been completed, additional offset calibrations can be
performed by themselves to adjust the zero reference point to a
new system zero reference value. This second system calibration
mode uses an input voltage for the zero-scale calibration point
but uses the VREF value for the full-scale point.
SYSTEM
REF HI
AIN
SYSTEM
REF LO
ANALOG
MUX
A0
A1
SIGNAL
CONDITIONING
AD7703
SCLK
SDATA
CAL
SC1
SC2
MICRO-
COMPUTER
AIN
Figure 12. Typical Connections for System Calibration
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| AD7703AR-REEL | 功能描述:IC ADC 20BIT LC2MOS MONO 20-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 |
| AD7703ARZ | 功能描述:IC ADC 20BIT LC2MOS 20-SOIC RoHS:是 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 |
| AD7703BN | 功能描述:IC ADC 20BIT LC2MOS 20-DIP 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:- |
| AD7703BNZ | 功能描述:IC ADC 20BIT LC2MOS MONO 20DIP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 其它有关文件:TSA1204 View All Specifications 标准包装:1 系列:- 位数:12 采样率（每秒）:20M 数据接口:并联 转换器数目:2 功率耗散（最大）:155mW 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:48-TQFP 供应商设备封装:48-TQFP（7x7） 包装:Digi-Reel® 输入数目和类型:4 个单端，单极；2 个差分，单极 产品目录页面:1156 (CN2011-ZH PDF) 其它名称:497-5435-6 |
| AD7703BQ | 制造商:AD 制造商全称:Analog Devices 功能描述:LC2MOS 20-Bit A/D Converter |
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