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参数资料
| 型号： | ALD500RA-10SEL |
| 厂商： | Advanced Linear Devices Inc |
| 文件页数： | 2/12页 |
| 文件大小： | 0K |
| 描述： | IC ADC 17BIT 20SOIC |
| 标准包装： | 36 |
| 位数： | 17 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 10mW |
| 电压电源： | 双 ± |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SOIC |
| 供应商设备封装： | 20-SOIC |
| 包装： | 管件 |
| 输入数目和类型： | * |
10
Advanced Linear Devices
ALD500RAU/ALD500RA/ALD500R
APPLICATIONS AND DESIGN NOTES
Determination and Selection of System Variables
The procedure outlined below allows the user to determine the
values for the following ALD500RAU/ALD500RA/ALD500R
system design variables:
(1) Determine Input Voltage Range
(2) Clock Frequency and Resolution Selection
(3) Input Integration Phase Timing
(4) Integrator Timing Components (RINT, CINT)
(5) Auto Zero and Reference Capacitors
(6) Voltage Reference
System Timing
Figure 3 and Figure 4 show the overall timing for a typical
system in which ALD500RAU/ALD500RA/ALD500R is
interfaced to a microcontroller. The microcontroller drives the
A, B inputs with I/O lines and monitors the comparator output,
COUT, using an I/O line or dedicated timer-capture control pin.
It may be necessary to monitor the state of the comparator
output in addition to having it control a timer directly during the
Reference Deintegration Phase.
There are four critical timing events:
sampling the input
polarity; capturing the deintegration time; minimizing overshoot
and properly executing the Integrator Output Zero Phase.
Selecting Input Integration Time
For maximum 50/60 cycle noise rejection, Input Integration
Time must be picked as a multiple of the period of line
frequency. For example, tINT times of 33msec, 66msec and
100 msec maximize 60Hz line rejection, and 20msec, 40
msec, 80msec, and 100 msec maximize 50Hz line rejection.
Note that tINT of 100 msec maximizes both 60 Hz and 50Hz
line rejection.
INT and DINT Phase Timing
The duration of the Reference Deintegrate Phase (DINT) is a
function of the amount of voltage charge stored on the
integrator capacitor during INT phase, and the value of VREF.
The DINT phase must be initiated immediately following INT
phase and terminated when an integrator output zero-crossing
is detected.
In general, the maximum number of counts
chosen for DINT phase is twice to three times that of INT phase
with VREF chosen as a maximum voltage relative to VIN. For
example, VREF = VIN(max)/2 would be a good reference
voltage.
Integrating Resistor (RINT )
The desired full-scale input voltage and amplifier output
current capability determine the value of RINT. The buffer and
integrator amplifiers each have a full-scale current of 20
A.
The value of RINT is therefore directly calculated as follows:
RINT
=VIN MAX / 20 A
where:
VIN MAX = Maximum input voltage desired
(full count voltage)
RINT
= Integrating Resistor value
For minimum noise and maximum linearity, RINT should be in
the range of between 50k
to 150k .
Integrating Capacitor (CINT)
The integrating capacitor should be selected to maximize
integrator output voltage swing VINT, for a given integration
time, without output level saturation. For +/-5V supplies,
recommended VINT range is between +/- 3 Volt to +/-4 Volt.
Using the 20
A buffer maximum output current, the value of
the integrating capacitor is calculated as follows:
CINT = (tINT) . (20 x 10
-6) / VINT
where: tINT
=
Input Integration Phase Period
VINT =
Maximum integrator output
voltage swing
It is critical that the integrating capacitor must have a very low
dielectric absorption, as charge loss or gain during conversion
directly converts into an error voltage. Polypropylene capacitors
are recommended while Polyester and Polybicarbonate
capacitors may also be used in less critical applications.
Reference (CREF) and Auto Zero (CAZ) Capacitors
CREF and CAZ must be low leakage capacitors (e.g.
polypropylene types). The slower the conversion rate, the
larger the value CREF must be. Recommended capacitor
values for CREF and CAZ are equal to CINT. Larger values for
CAZ and CREF may also be used to limit roll-over errors.
Calculate VREF
The reference deintegration voltage is calculated using:
VREF = (VINT) . (CINT) . (RINT) / 2(tINT)
The ALD500RAU/ALD500RA/ALD500R requires an external
RREF in order to operate properly. This RREF should be a 1%
metal film 100K
resistor, 50 ppm/C. Any other loading must
be high impedance (
≥100M).
Converter Noise
The converter noise is the total algebraic sum of the integrator
noise and the comparator noise. This value is typically 14
V
peak to peak. The higher the value of the reference voltage,
the lower the converter noise. Such sources of noise errors
can be reduced by increased integration times, which effectively
filter out any such noise. If the integration time periods are
selected as multiples of 50/60Hz frequencies, then 50/60Hz
noise is also rejected, or averaged out. The signal-to-noise
ratio is related to the integration time (tINT) and the integration
time constant (RINT) (CINT) as follows:
S/N (dB) = 20 Log ((VINT / 14 x 10
-6) . tINT /(RINT . CINT))
This converter noise can also be reduced by using multiple
samples and mathematically averaged. For example, taking
16 samples and averaging the readings result in a mathematical
(by software) filtering of noise to less than 4
V.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ALD500RA-20PE | 制造商:ALD 制造商全称:Advanced Linear Devices 功能描述:PRECISION INTEGRATING ANALOG PROCESSOR WITH PRECISION VOLTAGE REFERENCE |
| ALD500RA-20PEI | 制造商:ALD 制造商全称:Advanced Linear Devices 功能描述:PRECISION INTEGRATING ANALOG PROCESSOR WITH PRECISION VOLTAGE REFERENCE |
| ALD500RA-20PEIL | 功能描述:模数转换器 - ADC 17 Bt A/D w20 ppm VR 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 |
| ALD500RA-20PEL | 功能描述:模数转换器 - ADC 17 Bt A/D w20 ppm VR 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 |
| ALD500RA-20QE | 制造商:ALD 制造商全称:Advanced Linear Devices 功能描述:PRECISION INTEGRATING ANALOG PROCESSOR WITH PRECISION VOLTAGE REFERENCE |
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