SBAS876C August   2018  – June 2019 ADS9224R , ADS9234R

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application 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: ADS92x4R
    6. 6.6  Electrical Characteristics: ADS9224R
    7. 6.7  Electrical Characteristics: ADS9234R
    8. 6.8  Timing Requirements
    9. 6.9  Switching Characteristics
    10. 6.10 Typical Characteristics: ADS9224R
    11. 6.11 Typical Characteristics: ADS9234R
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Converter Modules
        1. 7.3.1.1 Analog Input With Sample-and-Hold
        2. 7.3.1.2 ADC Transfer Function
      2. 7.3.2 Internal Reference Voltage
      3. 7.3.3 Reference Buffers
      4. 7.3.4 REFby2 Buffer
      5. 7.3.5 Data Averaging
        1. 7.3.5.1 Averaging of Two Samples
        2. 7.3.5.2 Averaging of Four Samples
    4. 7.4 Device Functional Modes
      1. 7.4.1 ACQ State
      2. 7.4.2 CNV State
      3. 7.4.3 Reset or Power-Down
        1. 7.4.3.1 Reset
        2. 7.4.3.2 Power-Down
      4. 7.4.4 Conversion Control and Data Transfer Frame
        1. 7.4.4.1 Conversion Control and Data Transfer Frame With Zero Cycle Latency (Zone 1 Transfer)
        2. 7.4.4.2 Conversion Control and Data Transfer Frame With Wide Read Cycle (Zone 2 Transfer)
    5. 7.5 READY/STROBE Output
      1. 7.5.1 READY Output
      2. 7.5.2 STROBE Output
    6. 7.6 Programming
      1. 7.6.1 Output Data Word
      2. 7.6.2 Data Transfer Protocols
        1. 7.6.2.1 Protocols for Reading From the Device
          1. 7.6.2.1.1 Legacy, SPI-Compatible Protocols (SPI-xy-S-SDR)
          2. 7.6.2.1.2 SPI-Compatible Protocols With Bus Width Options and Single Data Rate (SPI-xy-D-SDR and SPI-xy-Q-SDR)
          3. 7.6.2.1.3 SPI-Compatible Protocols With Bus Width Options and Double Data Rate (SPI-x1-S-DDR, SPI-x1-D-DDR, SPI-x1-Q-DDR)
          4. 7.6.2.1.4 Clock Re-Timer (CRT) Protocols (CRT-S-SDR, CRT-D-SDR, CRT-Q-SDR, CRT-S-DDR, CRT-D-DDR, CRT-Q-DDR)
          5. 7.6.2.1.5 Parallel Byte Protocols (PB-xy-AB-SDR, PB-xy-AA-SDR)
        2. 7.6.2.2 Device Setup
          1. 7.6.2.2.1 Single Device: All Enhanced-SPI Options
          2. 7.6.2.2.2 Single Device: Minimum Pins for a Standard SPI Interface
        3. 7.6.2.3 Protocols for Configuring the Device
      3. 7.6.3 Reading and Writing Registers
    7. 7.7 Register Maps
      1. 7.7.1 ADS92x4R Registers
        1. 7.7.1.1 DEVICE_STATUS Register (Offset = 0h) [reset = 0h]
          1. Table 12. DEVICE_STATUS Register Field Descriptions
        2. 7.7.1.2 POWER_DOWN_CFG Register (Offset = 1h) [reset = 0h]
          1. Table 13. POWER_DOWN_CFG Register Field Descriptions
        3. 7.7.1.3 PROTOCOL_CFG Register (Offset = 2h) [reset = 0h]
          1. Table 14. PROTOCOL_CFG Register Field Descriptions
        4. 7.7.1.4 BUS_WIDTH Register (Offset = 3h) [reset = 0h]
          1. Table 15. BUS_WIDTH Register Field Descriptions
        5. 7.7.1.5 CRT_CFG Register (Offset = 4h) [reset = 0h]
          1. Table 16. CRT_CFG Register Field Descriptions
        6. 7.7.1.6 OUTPUT_DATA_WORD_CFG Register (Offset = 5h) [reset = 0h]
          1. Table 17. OUTPUT_DATA_WORD_CFG Register Field Descriptions
        7. 7.7.1.7 DATA_AVG_CFG Register (Offset = 6h) [reset = 0h]
          1. Table 18. DATA_AVG_CFG Register Field Descriptions
        8. 7.7.1.8 REFBY2_OFFSET Register (Offset = 7h) [reset = 0h]
          1. Table 19. REFBY2_OFFSET Register Field Descriptions
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 ADC Input Driver
        1. 8.1.1.1 Charge-Kickback Filter
      2. 8.1.2 Input Amplifier Selection
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Signal Path
      2. 10.1.2 Grounding and PCB Stack-Up
      3. 10.1.3 Decoupling of Power Supplies
      4. 10.1.4 Reference Decoupling
      5. 10.1.5 Differential Input Decoupling
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2 Detailed Design Procedure

Figure 80 shows an application circuit for this example. The device incorporates an internal 2.5-V reference voltage and independent matched reference buffers for each ADC. The internal reference output (REFOUT) is decoupled with a 1-µF capacitor. The matched reference buffers provide a gain of 1.6384 V/V and generate a high-precision, 4.096-V reference voltage for each ADC channel. Decouple the reference buffer outputs (the REFP_A and REFP_B pins) with the REFM_A and REFM_B pins, respectively, with 10-µF decoupling capacitors. The circuit in Figure 80 shows a fully-differential data acquisition (DAQ) block optimized for low distortion and noise using the THS4551 and the ADS92x4R. Both differential ADC inputs are driven using a high-bandwidth, low-distortion, fully differential amplifier (FDA) designed in a gain of 1 V/V and an optimal RC charge-kickback filter before going to the ADC. Generally, the distortion from the input driver must be at least 10 dB less than the ADC distortion. Therefore, these circuits use the low-power THS4551 as an input driver that provides exceptional AC performance because of its extremely low-distortion and high bandwidth specifications. In addition, the components of the charge kickback filter are selected to keep the noise from the front-end circuit low without adding distortion. This front-end circuit configuration requires a differential signal at the input of the FDA and provides a differential output to drive the ADC inputs. The FDA establishes a fixed common-mode voltage at the ADC inputs using the VOCM input pin from the FDA. The ADS92x4R incorporates a REFby2 buffer output for setting the common-mode voltage. The ADS92x4R REFby2 output is decoupled using a 1-µF capacitor and connected to each FDA VOCM input pin. Each VOCM pin is decoupled using a 0.1-µF capacitor. For a complete schematic, see the ADS9224REVM-PDK user's guide located in the ADS9224R SAR analog to digital converter evaluation module tool folder.