SBAU351 April   2021

 

  1.   Trademarks
  2. 1EVM Overview
    1. 1.1 ADS127L11EVM Kit
    2. 1.2 ADS127L11EVM Board
    3. 1.3 ADS127L11EVM-PDK-GUI Unsupported Features
  3. 2EVM Analog Interface
    1. 2.1 EVM Analog Input Options
    2. 2.2 ADC Connections and Decoupling
    3. 2.3 ADC Input Drive Amplifiers
    4. 2.4 VCOM Buffer
    5. 2.5 Onboard Voltage Reference
    6. 2.6 External Voltage Reference
    7. 2.7 Clock Tree
  4. 3Digital Interface
    1. 3.1 Serial Interface (SPI)
    2. 3.2 I2C Bus for Onboard EEPROM
  5. 4Power Supplies
    1. 4.1 Power Connection and Configuration
    2. 4.2 Low Dropout Regulator (LDO)
  6. 5ADS127L11EVM Software Installation
  7. 6EVM Operation
    1. 6.1 Connecting the Hardware
    2. 6.2 Optional Connections to the EVM
    3. 6.3 EVM GUI Global Settings for ADC Control
    4. 6.4 Time Domain Display
    5. 6.5 Frequency Domain Display
    6. 6.6 Histogram Display
  8. 7Bill of Materials, Schematics, and Layout
    1. 7.1 Bill of Materials
    2. 7.2 Board Layouts
    3. 7.3 Schematics
  9. 8References

2.3 ADC Input Drive Amplifiers

The circuit shown in Figure 2-2 is the fully differential amplifier (THS4551) used to drive the ADC. The input applied to J3 and J6 must be a low-distortion differential signal. The common-mode output for the amplifier is controlled by pin 2 on U5 (VOCM). The common-mode signal is set by the data converter (pin 6, VCM). The output of the amplifier connects to an RC filter that connects to the ADC input (R37, R43, C30, C26, and C32). The amplified configuration has several do not populate (DNP) components. These components provide flexibility, but are not required for good performance. The amplifier power supplies are connected by default to the AVDD and AVSS supplies that are also used for the ADC. The amplifier supplies can be changed to external supplies VP and VM by removing the 0-Ω resistors that connect to AVDD and AVSS (0R31 and 0R47), and installing them to connect VP and VM (0R32 and 0R48).

GUID-20210331-CA0I-F2DC-WLXB-X9NK7SQJVCLZ-low.svgFigure 2-2 ADC Drive Amplifier