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参数资料
| 型号： | AD7247A |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | LC2MOS Dual 12-Bit DACPORTs |
| 中文描述： | LC2MOS双12位DACPORTs |
| 文件页数： | 8/12页 |
| 文件大小： | 392K |
| 代理商： | AD7247A |
AD7237A/AD7247A
REV. 0
–8–
CIRCUIT INFORMATION
D/A Section
The AD7237A/AD7247A contains two 12-bit voltage-mode D/A
converters consisting of highly stable thin film resistors and high
speed NMOS single-pole, double-throw switches. The output
voltage from the converters has the same polarity as the refer-
ence voltage, REF IN, allowing single supply operation. The
simplified circuit diagram for one of the D/A converters is
shown in Figure 2.
The REF IN voltage is internally buffered by a unity gain
amplifier before being applied to the D/A converters. The D/A
converters are configured and scaled for a 5 V reference and the
device is tested with 5 V applied to REF IN.
Figure 2. D/A Simplified Circuit Diagram
Internal Reference
The AD7237A/AD7247A has an on-chip temperature compen-
sated buried Zener reference (see Figure 3) which is factory
trimmed to 5 V
±
30 mV (
±
50 mV for T Version). The reference
voltage is provided at the REF OUT pin. This reference can be
used to provide the reference voltage for the D/A converter (by
connecting the REF OUT pin to the REF IN pin) and the offset
voltage for bipolar outputs (by connecting REF OUT to R
OFS
).
The reference voltage can also be used as a reference for other
components and is capable of providing up to 500
μ
A to an ex-
ternal load. The maximum recommended capacitance on REF
OUT for normal operation is 50 pF. If the reference is required
for external use, it should be decoupled to AGND (GND) with
a 200
resistor in series with parallel combination of a 10
μ
F
tantalum capacitor and a 0.1
μ
F ceramic capacitor.
Figure 3. Internal Reference
External Reference
In some applications, the user may require a system reference or
some other external reference to drive the AD7237A/ AD7247A
reference input. References such as the AD586 5 V reference
provide the ideal external reference source for the AD7237A/
AD7247A (see Figure 9).
Op Amp Section
The output of the voltage-mode D/A converter is buffered by a
noninverting CMOS amplifier. The R
OFS
input allows different
output voltage ranges to be selected. The buffer amplifier is ca-
pable of developing +10 V across a 2 k
load to GND. The
output amplifier can be operated from a single +12 V to +15 V
supply by tying V
SS
= 0 V. The amplifier can also be operated
from dual supplies (
±
12 V to
±
15 V) to allow a bipolar output
range of –5 V to +5 V. The advantages of having dual supplies
for the unipolar output ranges are faster settling time to voltages
near 0 V, full sink capability of 2.5 mA maintained over the en-
tire output range and the elimination of the effects of negative
offsets on the transfer characteristic (outlined previously). A
plot of the single supply output sink capability of the amplifier is
shown in the Typical Performance Graphs section.
INTERFACE LOGIC INFORMATION—AD7247A
Table I shows the truth table for AD7247A operation. The part
contains a single, parallel 12-bit latch for each DAC. It can be
treated as two independent DACs, each with its own
CS
input
and a common
WR
input.
CSA
and
WR
control the loading of
data to the DAC A latch while
CSB
and
WR
control the loading
of the DAC B latch. If
CSA
and
CSB
are both low, with
WR
low, the same data will be written to both DAC latches. All con-
trol signals are level triggered and therefore either or both
latches can be made transparent. Input data is latched to the re-
spective latch on the rising edge of
WR
. Figure 4 shows the in-
put control logic for the AD7247A, while the write cycle timing
diagram for the part is shown in Figure 5.
Figure 4. AD7247A Input Control Logic
Figure 5. AD7247A Write Cycle Timing Diagram
相关PDF资料 |
PDF描述 |
|---|---|
| AD7237A | LC2MOS Dual 12-Bit DACPORTs |
| AD7237AAN | CAPACITOR, 10UF, 50V ELECTROLYTIC, RADIAL |
| AD7237AAR | LC2MOS Dual 12-Bit DACPORTs |
| AD7237ABN | 10K 10-TURN WW 1/4 DIA SHAFT |
| AD7237ABR | LC2MOS Dual 12-Bit DACPORTs |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD7247AAN | 功能描述:IC DAC 12BIT W/AMP W/BUFF 24-DIP RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:DACPORT® 产品培训模块:Data Converter Fundamentals DAC Architectures 标准包装:750 系列:- 设置时间:7µs 位数:16 数据接口:并联 转换器数目:1 电压电源:双 ± 功率耗散（最大）:100mW 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-LCC（J 形引线） 供应商设备封装:28-PLCC（11.51x11.51） 包装:带卷 (TR) 输出数目和类型:1 电压，单极；1 电压，双极 采样率（每秒）:143k |
| AD7247AANZ | 功能描述:IC DAC 12BIT W/AMP W/BUFF 24-DIP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:DACPORT® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 设置时间:4µs 位数:12 数据接口:串行 转换器数目:2 电压电源:单电源 功率耗散（最大）:- 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 供应商设备封装:8-uMAX 包装:管件 输出数目和类型:2 电压，单极 采样率（每秒）:* 产品目录页面:1398 (CN2011-ZH PDF) |
| AD7247AAR | 功能描述:IC DAC 12BIT W/AMP W/BUFF 24SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:DACPORT® 产品培训模块:Data Converter Fundamentals DAC Architectures 标准包装:750 系列:- 设置时间:7µs 位数:16 数据接口:并联 转换器数目:1 电压电源:双 ± 功率耗散（最大）:100mW 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-LCC（J 形引线） 供应商设备封装:28-PLCC（11.51x11.51） 包装:带卷 (TR) 输出数目和类型:1 电压，单极；1 电压，双极 采样率（每秒）:143k |
| AD7247AAR-REEL | 制造商:Analog Devices 功能描述:DAC 2-CH R-2R 12-bit 24-Pin SOIC W T/R 制造商:Analog Devices 功能描述:DAC 2CH R-2R 12-BIT 24SOIC W - Tape and Reel |
| AD7247AAR-REEL7 | 功能描述:IC DAC 12BIT W/AMP W/BUFF 24SOIC RoHS:否 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:DACPORT® 产品培训模块:Data Converter Fundamentals DAC Architectures 标准包装:750 系列:- 设置时间:7µs 位数:16 数据接口:并联 转换器数目:1 电压电源:双 ± 功率耗散（最大）:100mW 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-LCC（J 形引线） 供应商设备封装:28-PLCC（11.51x11.51） 包装:带卷 (TR) 输出数目和类型:1 电压，单极；1 电压，双极 采样率（每秒）:143k |
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