SBAU269C October   2016  – August 2021 ADS8900B

 

  1.   Trademarks
  2. 1EVM Overview
    1. 1.1 ADS8900EVM-PDK Kit Features
    2. 1.2 ADS8900EVM Features
  3. 2Analog Interface
    1. 2.1 ADS8900B Connections and Decoupling
    2. 2.2 ADC Amplifier Input Drive
    3. 2.3 Voltage Reference and VCM Scaling
  4. 3Digital Interface
    1. 3.1 multiSPI™ for ADC Digital I/O
    2. 3.2 I2C Bus for Onboard EEPROM
  5. 4Power Supplies
    1. 4.1 Positive Supply and Test Points
    2. 4.2 Negative Supply
  6. 5ADS8900EVM-PDK Initial Setup
    1. 5.1 Software Installation
    2. 5.2 Default Jumper Settings for Differential Inputs
    3. 5.3 Default Jumpers for Bipolar, Single-Ended Inputs
    4. 5.4 Default Jumpers for Unipolar, Single-Ended Inputs
    5. 5.5 External Source Requirements for ADS8900 Evaluation
  7. 6ADS8900EVM-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
    7. 6.7 ADS8900BEVM Support for ADS8910B and ADS8920B Devices
  8. 7Bill of Materials, PCB Layout, and Schematics
    1. 7.1 Bill of Materials (BOM)
    2. 7.2 PCB Layout
    3. 7.3 Schematics
  9. 8Revision History

6.6 Linearity Analysis Tool

The linearity analysis tool (shown in Figure 6-9) measures and generates the DNL and INL plots over code for the specific ADS8900 installed in the evaluation board. This tool requires a 2-kHz sinusoidal input signal, which is slightly saturated (35 mV outside the full-scale range at each input or 0.13 dBFS) with very low distortion. The external source linearity must be better than the ADC linearity to ensure that the measured system performance reflects the linearity errors of the ADC and is not limited by the performance of the signal source. To make sure that the DNL and INL of the ADC are correctly measured, the external source must meet the requirements in Section 5.5.

CAUTION:

This tool requires a negative supply on the THS4551 driver amplifier (U2). The easiest way to provide the negative supply is to install the negative charge pump LM7705 (U6). Also install the output filter capacitors and resistor associated with this charge pump (C31, C32, C33, C34, C35, C36, and R41).

The number-of-hits setting depends on the external noise source. For a 110-dB SNR external source with approximately 10 µVrms of noise, the total number of hits must be 512. For a source with 100-dB SNR, the recommended number of hits is 1024.

Note:

This analysis can take a couple of minutes to run and the evaluation board must remain undisturbed during the complete duration of the analysis.

GUID-AC439334-A9B9-478E-8D9E-EEE90491C90F-low.pngFigure 6-9 Linearity Analysis Tool