SBAS580D May   2013  – March 2018 ADS7250 , ADS7850 , ADS8350

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Functional Block Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Electrical Characteristics: All Devices
    6. 6.6  Electrical Characteristics: ADS7250
    7. 6.7  Electrical Characteristics: ADS7850
    8. 6.8  Electrical Characteristics: ADS8350
    9. 6.9  Timing Requirements
    10. 6.10 Switching Characteristics
    11. 6.11 Typical Characteristics: ADS7250
    12. 6.12 Typical Characteristics: ADS7850
    13. 6.13 Typical Characteristics: ADS8350
    14. 6.14 Typical Characteristics: All Devices
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Reference
      2. 7.3.2 Analog Input
        1. 7.3.2.1 Analog Input Full-Scale Range
      3. 7.3.3 ADC Transfer Function
    4. 7.4 Device Functional Modes
      1. 7.4.1 Serial Interface
      2. 7.4.2 Short-Cycling, Frame Abort, and Reconversion Feature
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 DAQ Circuit: Maximum SINAD for a 10-kHz Input Signal at 750-kSPS Throughput
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 ADC Reference Driver
          2. 8.2.1.2.2 ADC Input Driver
            1. 8.2.1.2.2.1 Input Amplifier Selection
            2. 8.2.1.2.2.2 Antialiasing Filter
        3. 8.2.1.3 Application Curve
      2. 8.2.2 DAQ Circuit: Maximum SINAD for a 100-kHz Input Signal at 750-kSPS Throughput
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 ADC Reference Driver
          2. 8.2.2.2.2 ADC Input Driver
        3. 8.2.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.2.2.2 ADC Input Driver

Refer to ADC Input Driver section for the detailed design procedure for an ADC input driver.

The application circuit shown in Figure 60 is optimized to achieve lowest distortion and lowest noise for a 100-kHz input signal. The input signal is processed through a high-bandwidth, low-distortion amplifier in an inverting gain configuration and a low-pass RC filter before being fed into the ADS8350 operating at 750-kSPS throughput.

As a rule of thumb, the distortion from the input driver should be at least 10 dB less than the ADC distortion. The distortion resulting from variation in the common-mode signal is eliminated by using the amplifier in an inverting gain configuration that establishes a fixed common-mode level for the circuit. This configuration also eliminates the requirement of a rail-to-rail swing at the input of the amplifier. The THS4032, used as an input driver, provides exceptional ac performance because of its extremely low-distortion, low-noise, and high-bandwidth specifications. The ADC AINM pin is also driven to VREF with the same amplifier to match the source impedance and to take full advantage of the pseudo-differential input structure of the ADC. In addition, the components of the antialiasing filter are such that the noise from the front-end circuit is kept low without adding distortion to the input signal.

NOTE

The same circuit can be used with the ADS7250 and ADS7850 to achieve their rated specifications.