SBAS752B May   2017  – October 2018 ADS122U04

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      K-Type Thermocouple Measurement
  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
    6. 6.6 UART Timing Requirements
    7. 6.7 UART Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Noise Performance
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Multiplexer
      2. 8.3.2  Low-Noise Programmable Gain Stage
        1. 8.3.2.1 PGA Input Voltage Requirements
        2. 8.3.2.2 Bypassing the PGA
      3. 8.3.3  Voltage Reference
      4. 8.3.4  Modulator and Internal Oscillator
      5. 8.3.5  Digital Filter
      6. 8.3.6  Conversion Times
      7. 8.3.7  Excitation Current Sources
      8. 8.3.8  Sensor Detection
      9. 8.3.9  System Monitor
      10. 8.3.10 Temperature Sensor
        1. 8.3.10.1 Converting From Temperature to Digital Codes
          1. 8.3.10.1.1 For Positive Temperatures (For Example, 50°C):
          2. 8.3.10.1.2 For Negative Temperatures (For Example, –25°C):
        2. 8.3.10.2 Converting From Digital Codes to Temperature
      11. 8.3.11 Offset Calibration
      12. 8.3.12 Conversion Data Counter
      13. 8.3.13 Data Integrity
      14. 8.3.14 General-Purpose Digital Inputs/Outputs
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
        1. 8.4.1.1 Power-On Reset
        2. 8.4.1.2 RESET Pin
        3. 8.4.1.3 Reset by Command
      2. 8.4.2 Conversion Modes
        1. 8.4.2.1 Single-Shot Conversion Mode
        2. 8.4.2.2 Continuous Conversion Mode
      3. 8.4.3 Operating Modes
        1. 8.4.3.1 Normal Mode
        2. 8.4.3.2 Turbo Mode
        3. 8.4.3.3 Power-Down Mode
    5. 8.5 Programming
      1. 8.5.1 UART Interface
        1. 8.5.1.1 Receive (RX)
        2. 8.5.1.2 Transmit (TX)
        3. 8.5.1.3 Data Ready (DRDY)
        4. 8.5.1.4 Protocol
        5. 8.5.1.5 Timeout
      2. 8.5.2 Data Format
      3. 8.5.3 Commands
        1. 8.5.3.1 RESET (0000 011x)
        2. 8.5.3.2 START/SYNC (0000 100x)
        3. 8.5.3.3 POWERDOWN (0000 001x)
        4. 8.5.3.4 RDATA (0001 xxxx)
        5. 8.5.3.5 RREG (0010 rrrx)
        6. 8.5.3.6 WREG (0100 rrrx dddd dddd)
        7. 8.5.3.7 Command Latching
      4. 8.5.4 Reading Data
        1. 8.5.4.1 Manual Data Read Mode
        2. 8.5.4.2 Automatic Data Read Mode
      5. 8.5.5 Data Integrity
    6. 8.6 Register Map
      1. 8.6.1 Configuration Registers
      2. 8.6.2 Register Descriptions
        1. 8.6.2.1 Configuration Register 0 (address = 00h) [reset = 00h]
          1. Table 18. Configuration Register 0 Field Descriptions
        2. 8.6.2.2 Configuration Register 1 (address = 01h) [reset = 00h]
          1. Table 19. Configuration Register 1 Field Descriptions
        3. 8.6.2.3 Configuration Register 2 (address = 02h) [reset = 00h]
          1. Table 21. Configuration Register 2 Field Descriptions
        4. 8.6.2.4 Configuration Register 3 (address = 03h) [reset = 00h]
          1. Table 22. Configuration Register 3 Field Descriptions
        5. 8.6.2.5 Configuration Register 4 (address = 04h) [reset = 00h]
          1. Table 23. Configuration Register 4 Field Descriptions
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Interface Connections
      2. 9.1.2 Analog Input Filtering
      3. 9.1.3 External Reference and Ratiometric Measurements
      4. 9.1.4 Establishing Proper Limits on the Absolute Input Voltage
      5. 9.1.5 Unused Inputs and Outputs
      6. 9.1.6 Pseudo Code Example
    2. 9.2 Typical Applications
      1. 9.2.1 K-Type Thermocouple Measurement (–200°C to +1250°C)
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 3-Wire RTD Measurement (–200°C to +850°C)
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Design Variations for 2-Wire and 4-Wire RTD Measurements
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Resistive Bridge Measurement
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
  10. 10Power Supply Recommendations
    1. 10.1 Power-Supply Sequencing
    2. 10.2 Power-Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

8.5.4.1 Manual Data Read Mode

In manual data read mode, data are read by issuing the RDATA command. The ADS122U04 responds to the RDATA command with the latest conversion data. There are three ways to monitor for new conversion data.

One way is to monitor for the falling edge of the DRDY signal. To configure the GPIO2/DRDY pin to output the DRDY signal, the pin must be configured as an output by setting the GPIO2DIR bit in the configuration register, and DRDY must be multiplexed to the pin by setting the GPIO2SEL bit in the configuration register.

Figure 62 shows the timing diagram for collecting data in manual data read mode using DRDY to indicate new data.

ADS122U04 ai_tim_continuous_conversion_drdy_bas752.gifFigure 62. Manual Data Read Mode Using DRDY (Continuous Conversion Mode)

Another way to monitor for a new conversion result is to periodically read the DRDY bit in the configuration register. If set, the DRDY bit indicates that a new conversion result is ready for retrieval. The host can subsequently issue an RDATA command to retrieve the data. The rate at which the host polls the ADS122U04 for new data must be at least as fast as the data rate in continuous conversion mode to prevent the host from missing a conversion result.

If a new conversion result becomes ready during a UART transmission, the transmission is not corrupted. The new data are loaded into the output shift register upon the following RDATA command.

Figure 63 shows the timing diagram for collecting data in manual data read mode using the DRDY bit in the configuration register to indicate new data.

ADS122U04 ai_tim_continuous_conversion_rreg_bas752.gifFigure 63. Manual Data Read Mode Using the RREG Command (Continuous Conversion Mode)

The last way to detect if new conversion data are available is through the use of the conversion data counter word. In this mode, the host periodically requests data from the device using the RDATA command and checks the conversion data counter word against the conversion data counter word read for the previous data received. If the counter values are the same, the host can disregard the data because that data has already been gathered. If the counter has incremented, the host records the data. The rate at which the host polls the ADS122U04 for new data must be at least as fast as the data rate in continuous conversion mode to prevent the host from missing a conversion result.

If a new conversion result becomes ready during a UART transmission, the transmission is not corrupted. The new data are loaded into the output shift register after the following RDATA command.

Figure 64 shows the timing diagram for collecting data in manual data read mode using the conversion data counter word to indicate new data.

ADS122U04 ai_tim_continuous_conversion_count_bas752.gifFigure 64. Manual Data Read Mode Using the Conversion Data Counter (Continuous Conversion Mode)

The conversion data counter can be used in conjunction with the previously discussed methods of detecting new data to ensure that the host did not miss a conversion result.