SBAU249A October   2015  – July 2025 ADS9110

 

  1.   1
  2.   2
  3.   Trademarks
  4. 1Evaluation Module Overview
    1. 1.1 ADS9110EVM-PDK Features
    2. 1.2 ADS9110EVM Features
  5. 2Analog Interface
    1. 2.1 Connectors for Differential Signal Source
    2. 2.2 ADC Differential Input Signal Driver
      1. 2.2.1 Input Signal Path
      2. 2.2.2 Input Common-Mode Jumper Configuration
      3. 2.2.3 R1 Setting vs Source Impedance
    3. 2.3 Onboard ADC Reference
  6. 3Digital Interfaces
    1. 3.1 multiSPI® for ADC Digital IO
  7. 4Power Supplies
  8. 5 ADS9110EVM-PDK Initial Setup
    1. 5.1 Default Jumper Settings
    2. 5.2 EVM Graphical User Interface (GUI) Software Installation
  9. 6 ADS9110EVM-PDK Operation
    1. 6.1 EVM GUI Global Settings for ADC Control
    2. 6.2 Register Map Configuration Tool
    3. 6.3 Time Domain Display Tool
    4. 6.4 Spectral Analysis Tool
    5. 6.5 Histogram Tool
    6. 6.6 Linearity Analysis Tool
  10. 7Hardware Design Files
    1. 7.1 Schematics
    2. 7.2 PCB Layout
    3. 7.3 Bill of Materials
  11. 8Revision History

2.2.3 R1 Setting vs Source Impedance

The external source impedance (RS) adds up to the 1kΩ of the input resistor, thereby moving the output common-mode of the OPA625 amplifiers. To compensate for this change in output common-mode, R1 can be modified according to the particular external source impedance value used with the evaluation board to allow full-scale input range without saturating the OPA625 amplifiers.

The board is shipped with R1 as 280kΩ that allows an external source impedance (RS) range between
0Ω to 32Ω for a 0V common-mode configuration (J1: closed and J2: closed). For floating or ac-coupled signals, the input common-mode is set by the OPA625 amplifiers themselves and R1 must remain at
280kΩ for any given source impedance. The ADC common-mode for 0V input common-mode setting is calculated using Equation 1.

Equation 1.

In the case of unipolar input signals with a 2.5V common-mode, the ADC common-mode is calculated using Equation 2.

Equation 2.

For Equation 1 and Equation 2, the value of R1 must be calculated to satisfy Equation 3:

Equation 3.