JAJSH03B May   2013  – February 2019 ADS8860

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      ADC 電源用に別個の LDO が不要
  4. 4 改訂履歴
  5. 5 概要（続き）
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements: 3-Wire Operation
    7. 8.7 Timing Requirements: 4-Wire Operation
    8. 8.8 Timing Requirements: Daisy-Chain
    9. 8.9 Typical Characteristics
  9. 9 Parameter Measurement Information
    1. 9.1 Equivalent Circuits
  10. 10Detailed Description
    1. 10.1 Overview
    2. 10.2 Functional Block Diagram
    3. 10.3 Feature Description
      1. 10.3.1 Analog Input
      2. 10.3.2 Reference
      3. 10.3.3 Clock
      4. 10.3.4 ADC Transfer Function
    4. 10.4 Device Functional Modes
      1. 10.4.1 CS Mode
        1. 10.4.1.1 3-Wire CS Mode Without a Busy Indicator
        2. 10.4.1.2 3-Wire CS Mode With a Busy Indicator
        3. 10.4.1.3 4-Wire CS Mode Without a Busy Indicator
        4. 10.4.1.4 4-Wire CS Mode With a Busy Indicator
      2. 10.4.2 Daisy-Chain Mode
        1. 10.4.2.1 Daisy-Chain Mode Without a Busy Indicator
        2. 10.4.2.2 Daisy-Chain Mode With a Busy Indicator
  11. 11Application and Implementation
    1. 11.1 Application Information
      1. 11.1.1 ADC Reference Driver
      2. 11.1.2 ADC Input Driver
        1. 11.1.2.1 Input Amplifier Selection
        2. 11.1.2.2 Charge-Kickback Filter
    2. 11.2 Typical Applications
      1. 11.2.1 DAQ Circuit for a 1-µs, Full-Scale Step Response
        1. 11.2.1.1 Design Requirements
        2. 11.2.1.2 Detailed Design Procedure
      2. 11.2.2 DAQ Circuit for Lowest Distortion and Noise Performance at 1 MSPS
        1. 11.2.2.1 Design Requirements
        2. 11.2.2.2 Detailed Design Procedure
      3. 11.2.3 Ultralow-Power DAQ Circuit at 10 kSPS
        1. 11.2.3.1 Design Requirements
        2. 11.2.3.2 Detailed Design Procedure
  12. 12Power Supply Recommendations
    1. 12.1 Power-Supply Decoupling
    2. 12.2 Power Saving
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
  14. 14デバイスおよびドキュメントのサポート
    1. 14.1 ドキュメントのサポート
      1. 14.1.1 関連資料
    2. 14.2 ドキュメントの更新通知を受け取る方法
    3. 14.3 コミュニティ・リソース
    4. 14.4 商標
    5. 14.5 静電気放電に関する注意事項
    6. 14.6 Glossary
  15. 15メカニカル、パッケージ、および注文情報

11.1.1 ADC Reference Driver

The external reference source to the ADS8860 must provide low-drift and very accurate voltage for the ADC reference input and support the dynamic charge requirements without affecting the noise and linearity performance of the device. The output broadband noise of most references can be in the order of a few hundred μVRMS. Therefore, to prevent any degradation in the noise performance of the ADC, the output of the voltage reference must be appropriately filtered by using a low-pass filter with a cutoff frequency of a few hundred hertz.

After band-limiting the noise of the reference circuit, the next important step is to design a reference buffer that can drive the dynamic load posed by the reference input of the ADC. The reference buffer must regulate the voltage at the reference pin such that the value of VREF stays within the 1-LSB error at the start of each conversion. This condition necessitates the use of a large capacitor, CBUF_FLT (see Figure 46) for regulating the voltage at the reference input of the ADC. The amplifier selected to drive the reference pin must have an extremely low offset and temperature drift with a low output impedance to drive the capacitor at the ADC reference pin without any stability issues.