groupUrl: https://ez.analog.com/dds/
Analog.com Analog Dialogue Wiki English
Analog.com Analog Dialogue Wiki 简体中文
EngineerZone
EngineerZone
  • Site
  • User
  • Site
  • Search
  • User
EngineerZone
EngineerZone
  • Log in
  • Site
  • Search
  • Log in
  • Home
  • Blogs ⌵
  • Browse ⌵
    • All Groups
    • All Members
  • Support ⌵
    • 3D ToF Depth Sensing
    • A2B
    • Aerospace and Defense (ADEF)
    • Amplifiers
    • Analog Microcontrollers
    • Analysis Control Evaluation (ACE) Software
    • Audio
    • Clock and Timing
    • Condition-Based Monitoring
    • Data Converters
    • Design Tools and Calculators
    • Direct Digital Synthesis (DDS)
    • Embedded Vision Sensing
    • Energy Monitoring and Metering
    • FPGA Reference Designs
    • Industrial Ethernet
    • Interface and Isolation
    • Low Power RF Transceivers
    • MEMS Inertial Sensors
    • Motor Control Hardware Platforms
    • Optical Sensing
    • Power Management
    • Precision Technology Signal Chains
    • Processors and DSP
    • Reference Circuits
    • RF and Microwave
    • Signal Chain Power (SCP)
    • Switches/Multiplexers
    • Temperature Sensors
    • Video
    • Wide Band RF Transceivers
    • Wireless Sensor Networks Reference Library
  • About EZ
  • More
  • Cancel
  • 主页
  • 浏览 ⌵
    • 收件箱
    • 个人设置
    • 会员
    • 专区列表
  • 论坛专区 ⌵
    • 放大器专区
    • 精密转换器专区
    • 音频专区
    • ADE电能计量专区
    • MEMS和传感器专区
    • 接口和隔离专区
    • Power 中文专区
    • ADUC微处理器专区
    • 锁相环专区
    • 开关和多路复用器专区
    • 温度传感器
    • 基准电压源专区
    • 资源库
    • 论坛使用指南
    • 技术支持参考库
    • 在线研讨会
    • 论坛社群活动
    • 论坛激励活动
  • More
  • Cancel
Direct Digital Synthesis (DDS)
Direct Digital Synthesis (DDS)
Documents AD9850 questions
  • Q&A
  • Discussions
  • Documents
  • Tags
  • Managers
  • More
  • Cancel
  • New
Direct Digital Synthesis (DDS) requires membership for participation - click to join
  • Documents
  • +AD5930: FAQ
  • +AD5932: FAQ
  • +AD5933: FAQ
  • +AD5934: FAQ
  • +AD9152: FAQ
  • +AD9830: FAQ
  • +AD9832: FAQ
  • +AD9833: FAQ
  • +AD9834: FAQ
  • +AD9835: FAQ
  • +AD9837: FAQ
  • +AD9838: FAQ
  • +AD9840: FAQ
  • +AD9840A: FAQ
  • +AD9845A: FAQ
  • -AD9850: FAQ
    • AD9850 questions
    • AD9850 searching for the "Dxocx.dll" AD9850_About Dxocx.dll file of AD9850EVB software
    • AD9850: Noise coupling on analog output
    • AD9850: output frequency
    • general usage of the AD9850
  • +AD9851: FAQ
  • +AD9852: FAQ
  • +AD9854: FAQ
  • +AD9854ASQ: FAQ
  • +AD9856: FAQ
  • +AD9857: FAQ
  • +AD9858: FAQ
  • +AD9859: FAQ
  • +AD9910: FAQ
  • +AD9912: FAQ
  • +AD9913: FAQ
  • +AD9914: FAQ
  • +AD9915: FAQ
  • +AD9945: FAQ
  • +AD9951: FAQ
  • +AD9952: FAQ
  • +AD9953: FAQ
  • +AD9954: FAQ
  • +AD9956: FAQ
  • +AD9957: FAQ
  • +AD9958: FAQ
  • +AD9959: FAQ
  • +DDS: FAQ
  • +Digital Ground (DGND): FAQ
  • +Evaluation Software: FAQ
  • +Frequency Ramp: FAQ
  • +I/O_UPDATE: FAQ
  • +Maximum Clock Rate: FAQ
  • +PLL: FAQ
  • +Programmable Modulus: FAQ
  • +SFDR: FAQ
  • +Thermally Enhanced Packages: FAQ

AD9850 questions

Q 

We design and prototype a signal generator. One of the requirements is precise
amplitude control. We are considering a design based on AD9850 followed by
AD8370. We propose to replace the Rset resistor on pin 12 of the AD9850 by a
mosfet constant current source, similar to app note AN-423 except that the
mosfet will be driven from an op-amp and DAC. I have some questions about
controlling the AD9850 output in this way:

1. Is the AD9850 DAC output current directly related to the current sourced by
pin 12? if so, what is the relationship?

2. What is the minimum voltage we can expect on pin 12? We need to know this so
that we can ensure that the constant current source does not saturate.

3. What is the range of current control we can use? The AD9850 data sheet shows
output current range of 5 to 20mA. Can we use control to below 5mA? if so, what
is a reasonable lower limit?

 

A 

1. Yes. DAC’s External RSET Connection. This resistor value sets the DAC
full-scale output current. For normal applications (FS IOUT = 10 mA), the value
for RSET is 3.9k connected to ground. The RSET/IOUT relationship is IOUT =
32(1.248 V/RSET).
I have attached a circuit diagram showing how the Rset is arranged to produce
the DAC full scale current at the DAC output.

2. Use the formulas above to calculate the voltages on pin 12.

3. We did not fully characterize the device below 5mA. As you go down in full
scale current, the DAC linear could start to distort. We’ve had customers work
down to 1mA full scale current with no complaints. Not sure how much below 1mA
you can go.

Attachments:
  • ad9850
  • Share
  • History
  • More
  • Cancel
Comments
Anonymous
Parents
  • analord
    analord over 5 years ago

    A design of mine also requires precise amplitude control.

    Current control on RSet via a ccs is one option, however is there any reason a  digipot such as the ad5258 (1K to 10K resistance range) is not a good solution? 

    Are there any implementation details I should be cautious of when placing a digipot on RSet? 

    • Cancel
    • Vote Up 0 Vote Down
    • Reply
    • More
    • Cancel
Comment
  • analord
    analord over 5 years ago

    A design of mine also requires precise amplitude control.

    Current control on RSet via a ccs is one option, however is there any reason a  digipot such as the ad5258 (1K to 10K resistance range) is not a good solution? 

    Are there any implementation details I should be cautious of when placing a digipot on RSet? 

    • Cancel
    • Vote Up 0 Vote Down
    • Reply
    • More
    • Cancel
Children
No Data
Related
 
社交网络
快速链接
  • 关于ADI
  • Partners
  • 模拟对话
  • 职业
  • 联系我们
  • 投资信息
  • 新闻中心
  • 质量和可靠性
  • 办事处与代理商
  • Analog Garage
语言
  • English
  • 简体中文
  • 日本語
  • Руccкий
电子快讯

欲获得最新ADI产品、设计工具、培训与活动的相关新闻与文章,请从我们的在线快讯中选出您感兴趣的产品类别,每月或每季度都会发送至您的收件箱。

订阅
Switch to mobile view
Analog Logo
© 1995 - 2022 Analog Devices, Inc. All Rights Reserved 沪ICP备09046653号-1
  • ©
  • 1995 - 2022 Analog Devices, Inc. All Rights Reserved
  • 沪ICP备09046653号-1
  • 网站地图
  • 隐私和保密政策
  • 隐私设置
  • 使用条款
 
Social
Quick Links
  • About ADI
  • Partners
  • Analog Dialogue
  • Careers
  • Contact us
  • Investor Relations
  • News Room
  • Quality & Reliability
  • Sales & Distribution
  • Analog Garage
Languages
  • English
  • 简体中文
  • 日本語
  • Руccкий
Newsletters

Interested in the latest news and articles about ADI products, design tools, training and events? Choose from one of our 12 newsletters that match your product area of interest, delivered monthly or quarterly to your inbox.

Sign Up
Switch to mobile view
Analog Logo
© 1995 - 2022 Analog Devices, Inc. All Rights Reserved 沪ICP备09046653号-1
  • ©
  • 1995 - 2022 Analog Devices, Inc. All Rights Reserved
  • 沪ICP备09046653号-1
  • Sitemap
  • Privacy & Security
  • Privacy Settings
  • Terms of use
EngineerZone Uses cookies to ensure you get the best experience in our community. For more information on cookies, please read our Privacy & Security Statement.