SBAU439 January   2024

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  8. 2Hardware
    1. 2.1 Analog Interface
      1. 2.1.1 ADC Channel Inputs
        1. 2.1.1.1 High-bandwidth, Fully-Differential Circuit: THS4551
        2. 2.1.1.2 Precision, High-CMRR Circuit: PGA855
      2. 2.1.2 Voltage Reference
    2. 2.2 Power Supplies
      1. 2.2.1 USB Power and When to Power the Board Externally
    3. 2.3 Digital Interface and Clock Inputs
      1. 2.3.1 Digital Interface Connections
      2. 2.3.2 Clock Select
    4. 2.4 ADS9227EVM Quick Start Guide
  9. 3Software
    1. 3.1 ADS9227EVM Software Reference
      1. 3.1.1 ADS9227EVM-GUI Software Installation
      2. 3.1.2 USB Driver Installation
      3. 3.1.3 Using the CONFIG Tab
      4. 3.1.4 Using the Capture Tab
      5. 3.1.5 Using the INL/DNL Tool
      6. 3.1.6 Using the Histogram Tab
  10. 4Hardware Design Files
    1. 4.1 Schematics
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials (BOM)
  11. 5Additional Information
    1.     Trademarks
  12. 6Related Documentation

2.1.1.1 High-bandwidth, Fully-Differential Circuit: THS4551

Figure 3-1 shows the schematic for the THS4551 input circuit connected to ADC A. The THS4551 is a precision, low-noise, fully differential amplifier with a gain-bandwidth product of 150MHz. This circuit is configured for a gain of 1V/V and can accept both single-ended and differential inputs. Install R3 and R4 as needed to support signal sources with 50-Ω output impedance.

The output common-mode voltage on the THS4551 is set by the voltage connected to the VOCM pin. When used with the ADS9227, TI recommends to buffer the VCMOUT voltage of the ADC before connecting to the VOCM pin of the THS4551. This makes sure that both amplifier outputs stay within the expected ADC input common-mode voltage range. The OPA320, shown in Figure 3-2, is used as the VCMOUT buffer to drive the output common-mode voltage on both ADC A and ADC B input circuits.

GUID-20240112-SS0I-G5ZB-7VQ8-18L5R4SZRQXJ-low.svgFigure 2-1 THS4551 Fully-Differential Circuit for ADC A
GUID-20240112-SS0I-ZRBW-9WQR-TKPCKVJZB9S6-low.svgFigure 2-2 OPA320 Circuit to Buffer the ADS9227 VCMOUT Voltage