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Download 电路笔记 CN-0055 AD5450/AD5451/AD5452/AD5453
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电路笔记 CN-0055 连接/参考器件 利用 ADI 公司产品进行电路设计 放心运用这些配套产品迅速完成设计。 欲获得更多信息和技术支持，请拨打 4006-100-006 或访问www.analog.com/zh/circuits 。 AD5450/AD5451/ AD5452/AD5453 8/10/12/14 位乘法 DAC AD8065 高性能 FastFET™ 放大器 采用 AD5450/AD5451/AD5452/AD5453 电流输出 DAC 系列的可编程增益元件 电路功能与优势 匹配。在要求增益大于 1 的电路中，推荐使用这种方法。 在要求DAC输出电压范围大于输入电压的应用中，可以采用 可 编 程 增 益 电 路 。 本 电 路 利 用 一 个 乘 法 DAC AD5450/ AD5451/AD5452/AD5453和一个快速、低失调运算放大器 其中 D 为载入 DAC 数字字。D = 0 至 255（8 位 AD5450）； AD8065提供可编程增益功能。最大增益值和温度系数由外部 D = 0 至 1023 （10 位 AD5451）； D = 0 至 4095（12 位 AD5452） ； 电阻设置，可编程增益分辨率由DAC的分辨率设置。 D = 0 至 16383（14 位 AD5453）；n 为位数。 电路描述 该电路的主要优势就是能够利用电阻匹配解决增益温度系数 图 1 所示电路就是推荐用来提高电路增益的方法。R1、R2 误差问题。外部电阻的温度系数需要彼此匹配，但不必与 和 R3 应具有相似的温度系数，但不必与 DAC 的温度系数相 DAC 内部梯形电阻的温度系数相匹配。 图 1. 采用电流输出 DAC 的可编程增益电路（原理示意图：未显示去耦和所有连接） Rev.A “Circuits from the Lab” from Analog Devices have been designed and built by Analog Devices engineers. Standard engineering practices have been employed in the design and construction of each circuit, and their function and performance have been tested and verified in a lab environment at room temperature. However, you are solely responsible for testing the circuit and determining its suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause whatsoever connected to the use of any “Circuit from the Lab”. (Continued on last page) One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2009 Analog Devices, Inc. All rights reserved. 电路笔记 CN-0055 要求用电阻 R1 是因为 DAC 的输入阻抗与 R1 之和必须等于 进一步阅读 RFB 与 R2||R3 之和的总反馈电阻。DAC 的输入阻抗为 RFB， ADIsimPower Design Tool. Analog Devices. 于是 Kester, Walt. The Data Conversion Handbook. Chapter 3, 7. Analog Devices. 2005. MT-015 Tutorial, Basic DAC Architectures II: Binary DACs. Analog Devices. R1 和 R2 的值必须适当选择，使得输出电压不超过运算放大 MT-031 Tutorial, Grounding Data Converters and Solving the 器的给定电源电压输出范围。另外还应注意，运算放大器的 Mystery of "AGND" and "DGND." Analog Devices. 偏置电流乘以总反馈电阻（RFB + R2||R3），即可产生相应 MT-033 Tutorial, Voltage Feedback Op Amp Gain and 的失调电压。因此，R1 和 R2 的值不能太大，否则将对总失 Bandwidth. Analog Devices. 调电压产生显著影响。 MT-035 Tutorial, Op Amp Inputs, Outputs, Single-Supply, and AD5450/AD5451/AD5452/AD5453 均采用 5 V CMOS工艺设 计，电源电压VDD1 为 2.5 V至 5.5 V。输出放大器采用双电源 电压驱动(VDD/VSS)，并且电压需要足够大才能适应电路的模 拟输出范围，一般为+/-12 V电源。4.7 pF电容用来防止闭环 应用中的响铃振荡或不稳定问题。 Rail-to-Rail Issues. Analog Devices. MT-101 Tutorial, Decoupling Techniques. Analog Devices. Voltage Reference Wizard Design Tool. Analog Devices. 数据手册和评估板 AD5450 Data Sheet 运算放大器的输入失调电压也会和电路的可变增益（由于存 AD5451 Data Sheet 在 DAC 的代码相关输出电阻）相乘。由于放大器的输入电压 AD5452 Data Sheet 出现失调，因而两个相邻数字小数之间的噪声增益变化会使 AD5453 Data Sheet 输出电压产生步进变化。此输出电压变化与两个代码间所需 AD8065 Data Sheet 的输出变化相叠加，引起差分线性误差；如果该误差足够大， OP1177 Data Sheet 可能会导致 DAC 非单调。AD8065 借助其低输入失调电压和 修订历史 低偏置电流特性可解决这一问题。 11/09—Rev. 0 to Rev. A 常见变化 OP1177是另一款适合该电流电压转换电路的优秀运算放大 器，它同样具有低失调电压和超低偏置电流特性。至于基准 Updated Format ................................................................ Universal 1/09—Revision 0: Initial Version 电压的选择，输入电压会受所选运算放大器的轨到轨电压限 制，增益则同样由电阻R2 和R3 设置。 (Continued from first page) "Circuits from the Lab" are intended only for use with Analog Devices products and are the intellectual property of Analog Devices or its licensors. While you may use the "Circuits from the Lab" in the design of your product, no other license is granted by implication or otherwise under any patents or other intellectual property by application or use of the "Circuits from the Lab". Information furnished by Analog Devices is believed to be accurate and reliable. However, "Circuits from the Lab" are supplied "as is" and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability, noninfringement or fitness for a particular purpose and no responsibility is assumed by Analog Devices for their use, nor for any infringements of patents or other rights of third parties that may result from their use. Analog Devices reserves the right to change any "Circuits from the Lab" at any time without notice, but is under no obligation to do so. Trademarks and registered trademarks are the property of their respective owners. ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. CN08620sc-0-11/09(A) w w w . a n a l o g . c o m Rev. A | Page 2 of 2
