SBAS817D November   2017  – June 2024 ADS8166 , ADS8167 , ADS8168

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Thermal Information
    4. 5.4 Recommended Operating Conditions
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Switching Characteristics
    8. 5.8 Timing Diagrams
    9. 5.9 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Analog Multiplexer
        1. 6.3.1.1 Multiplexer Configurations
        2. 6.3.1.2 Multiplexer With Minimum Crosstalk
        3. 6.3.1.3 Early Switching for Direct Sensor Interface
      2. 6.3.2 Reference
      3. 6.3.3 REFby2 Buffer
      4. 6.3.4 Converter Module
        1. 6.3.4.1 Internal Oscillator
        2. 6.3.4.2 ADC Transfer Function
      5. 6.3.5 Low-Dropout Regulator (LDO)
    4. 6.4 Device Functional Modes
      1. 6.4.1 Channel Selection Using Internal Multiplexer
        1. 6.4.1.1 Manual Mode
        2. 6.4.1.2 On-The-Fly Mode
        3. 6.4.1.3 Auto Sequence Mode
        4. 6.4.1.4 Custom Channel Sequencing Mode
      2. 6.4.2 Digital Window Comparator
    5. 6.5 Programming
      1. 6.5.1 Data Transfer Protocols
        1. 6.5.1.1 Enhanced-SPI Interface
          1. 6.5.1.1.1 Protocols for Configuring the Device
          2. 6.5.1.1.2 Protocols for Reading From the Device
            1. 6.5.1.1.2.1 SPI Protocols With a Single SDO
            2. 6.5.1.1.2.2 SPI Protocols With Dual SDO
            3. 6.5.1.1.2.3 Clock Re-Timer Data Transfer
              1. 6.5.1.1.2.3.1 Output Bus Width Options
      2. 6.5.2 Register Read/Write Operation
  8. 7 Register Maps
    1. 7.1 Interface and Hardware Configuration Registers
      1. 7.1.1 REG_ACCESS Register (address = 00h) [reset = 00h]
      2. 7.1.2 PD_CNTL Register (address = 04h) [reset = 00h]
      3. 7.1.3 SDI_CNTL Register (address = 008h) [reset = 00h]
      4. 7.1.4 SDO_CNTL1 Register (address = 0Ch) [reset = 00h]
      5. 7.1.5 SDO_CNTL2 Register (address = 0Dh) [reset = 00h]
      6. 7.1.6 SDO_CNTL3 Register (address = 0Eh) [reset = 00h]
      7. 7.1.7 SDO_CNTL4 Register (address = 0Fh) [reset = 00h]
      8. 7.1.8 DATA_CNTL Register (address = 10h) [reset = 00h]
      9. 7.1.9 PARITY_CNTL Register (address = 11h) [reset = 00h]
    2. 7.2 Device Calibration Registers
      1. 7.2.1 OFST_CAL Register (address = 18h) [reset = 00h]
      2. 7.2.2 REF_MRG1 Register (address = 19h) [reset = 00h]
      3. 7.2.3 REF_MRG2 Register (address = 1Ah) [reset = 00h]
      4. 7.2.4 REFby2_MRG Register (address = 1Bh) [reset = 00h]
    3. 7.3 Analog Input Configuration Registers
      1. 7.3.1 AIN_CFG Register (address = 24h) [reset = 00h]
      2. 7.3.2 COM_CFG Register (address = 27h) [reset = 00h]
    4. 7.4 Channel Sequence Configuration Registers Map
      1. 7.4.1 DEVICE_CFG Register (address = 1Ch) [reset = 00h]
      2. 7.4.2 CHANNEL_ID Register (address = 1Dh) [reset = 00h]
      3. 7.4.3 SEQ_START Register (address = 1Eh) [reset = 00h]
      4. 7.4.4 SEQ_ABORT Register (address = 1Fh) [reset = 00h]
      5. 7.4.5 ON_THE_FLY_CFG Register (address = 2Ah) [reset = 00h]
      6. 7.4.6 AUTO_SEQ_CFG1 Register (address = 80h) [reset = 00h]
      7. 7.4.7 AUTO_SEQ_CFG2 Register (address = 82h) [reset = 00h]
      8. 7.4.8 Custom Channel Sequencing Mode Registers
        1. 7.4.8.1 CCS_START_INDEX Register (address = 88h) [reset = 00h]
        2. 7.4.8.2 CCS_END_INDEX Register (address = 89h) [reset = 00h]
        3. 7.4.8.3 CCS_SEQ_LOOP Register (address = 8Ah) [reset = 00h]
        4. 7.4.8.4 CCS_CHID_INDEX_m Registers (address = 8C, 8E, 90, 92, 94, 96, 98, 9A, 9C, 9E, A0, A2, A4, A6, A8, and AAh) [reset = 00h]
        5. 7.4.8.5 REPEAT_INDEX_m Registers (address = 8D, 8F, 91, 93, 95, 97, 99, 9B, 9D, 9F, A1, A3, A5, A7, A9, and ABh) [reset = 00h]
    5. 7.5 Digital Window Comparator Configuration Registers Map
      1. 7.5.1  ALERT_CFG Register (address = 2Eh) [reset = 00h]
      2. 7.5.2  HI_TRIG_AINx[15:0] Register (address = 4Dh to 30h) [reset = 0000h]
      3. 7.5.3  LO_TRIG_AINx[15:0] Register (address = 71h to 54h) [reset = 0000h]
      4. 7.5.4  HYSTERESIS_AINx[7:0] Register (address = 4Fh to 33h) [reset = 00h]
      5. 7.5.5  ALERT_LO_STATUS Register (address = 78h) [reset = 00h]
      6. 7.5.6  ALERT_HI_STATUS Register (address = 79h) [reset = 00h]
      7. 7.5.7  ALERT_STATUS Register (address = 7Ah) [reset = 00h]
      8. 7.5.8  CURR_ALERT_LO_STATUS Register (address = 7Ch) [reset = 00h]
      9. 7.5.9  CURR_ALERT_HI_STATUS Register (address = 7Dh) [reset = 00h]
      10. 7.5.10 CURR_ALERT_STATUS Register (address = 7Eh) [reset = 00h]
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Multiplexer Input Connection
    2. 8.2 Typical Applications
      1. 8.2.1 1MSPS DAQ Circuit With Lowest Distortion and Noise Performance
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
    3.     Power Supply Recommendations
    4. 8.3 Layout
      1. 8.3.1 Layout Guidelines
        1. 8.3.1.1 Analog Signal Path
        2. 8.3.1.2 Grounding and PCB Stack-Up
        3. 8.3.1.3 Decoupling of Power Supplies
        4. 8.3.1.4 Reference Decoupling
        5. 8.3.1.5 Reference Buffer Decoupling
        6. 8.3.1.6 Multiplexer Input Decoupling
        7. 8.3.1.7 ADC Input Decoupling
        8. 8.3.1.8 Example Schematic
      2. 8.3.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

6.3.1.3 Early Switching for Direct Sensor Interface

Figure 6-4 shows the small-signal equivalent model of the ADS816x analog inputs. The multiplexer input has a switch resistance (RMUX) and parasitic capacitance (CMUX). The parasitic capacitance causes a charge kickback on the MUX analog input at the same time as the ADC sampling capacitor causes a charge kickback on ADC inputs.

ADS8166 ADS8167 ADS8168 Synchronous and Timed Switching of the MUX and ADC Input SwitchesFigure 6-4 Synchronous and Timed Switching of the MUX and ADC Input Switches

In conventional multichannel SAR ADCs, the acquisition time of the ADC is also the settling time available at the analog inputs of the multiplexer because these times are internally connected. Thus, high-bandwidth op amps are required at the analog inputs of the multiplexer to settle the charge kickback. However, multiple high-bandwidth op amps significantly increase power dissipation, cost, and size of the solution.

The analog inputs of the ADS816x provide a long settling time (tCYCLE – 100 ns), resulting in long acquisition time at the MUX inputs when using a driver amplifier between the MUX outputs and the ADC inputs. Figure 6-5 shows a timing diagram of this long acquisition phase. The low parasitic capacitance together with the enhanced settling time eliminate the need to use an op amp at the multiplexer input in most applications.

ADS8166 ADS8167 ADS8168 Early Switching of the MUX Enables a Long Acquisition PhaseFigure 6-5 Early Switching of the MUX Enables a Long Acquisition Phase