SBAS790C October   2018  – June 2019 ADS125H02

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Functional Block Diagram
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Noise Performance
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Input Range
      2. 9.3.2 Analog Inputs
        1. 9.3.2.1 ESD Diodes
        2. 9.3.2.2 Input Multiplexer
          1. 9.3.2.2.1 Analog Inputs (AIN0, AIN1, AINCOM)
          2. 9.3.2.2.2 High-Voltage Power Supply Readback
          3. 9.3.2.2.3 Internal VCOM Connection (Default)
          4. 9.3.2.2.4 Temperature Sensor
      3. 9.3.3 Programmable Gain Amplifier (PGA)
        1. 9.3.3.1 PGA Operating Range
        2. 9.3.3.2 PGA Monitor
      4. 9.3.4 Reference Voltage
        1. 9.3.4.1 Internal Reference
        2. 9.3.4.2 External Reference
        3. 9.3.4.3 AVDD Power-Supply Reference
        4. 9.3.4.4 Reference Monitor
      5. 9.3.5 Current Sources (IDAC1 and IDAC2)
      6. 9.3.6 General-Purpose Inputs and Outputs (GPIOs)
      7. 9.3.7 ADC Modulator
      8. 9.3.8 Digital Filter
        1. 9.3.8.1 Sinc Filter Mode
          1. 9.3.8.1.1 Sinc Filter Frequency Response
        2. 9.3.8.2 FIR Filter
        3. 9.3.8.3 50-Hz and 60-Hz Normal Mode Rejection
    4. 9.4 Device Functional Modes
      1. 9.4.1 Conversion Control
        1. 9.4.1.1 Continuous-Conversion Mode
        2. 9.4.1.2 Pulse-Conversion Mode
        3. 9.4.1.3 Conversion Latency
        4. 9.4.1.4 Start-Conversion Delay
      2. 9.4.2 Auto-Zero Mode
      3. 9.4.3 Clock Mode
      4. 9.4.4 Reset
        1. 9.4.4.1 Power-On Reset
        2. 9.4.4.2 Reset by Pin
        3. 9.4.4.3 Reset by Command
      5. 9.4.5 Calibration
        1. 9.4.5.1 Offset and Full-Scale Calibration
          1. 9.4.5.1.1 Offset Calibration Registers
          2. 9.4.5.1.2 Full-Scale Calibration Registers
        2. 9.4.5.2 Offset Calibration (OFSCAL)
        3. 9.4.5.3 Full-Scale Calibration (GANCAL)
        4. 9.4.5.4 Calibration Command Procedure
        5. 9.4.5.5 User Calibration Procedure
    5. 9.5 Programming
      1. 9.5.1 Serial Interface
        1. 9.5.1.1 Chip-Select Pins (CS1 and CS2)
        2. 9.5.1.2 Serial Clock (SCLK)
        3. 9.5.1.3 Data Input (DIN)
        4. 9.5.1.4 Data Output/Data Ready (DOUT/DRDY)
      2. 9.5.2 Data Ready (DRDY)
        1. 9.5.2.1 DRDY in Continuous-Conversion Mode
        2. 9.5.2.2 DRDY in Pulse-Conversion Mode
        3. 9.5.2.3 Data Ready by Software Polling
      3. 9.5.3 Conversion Data
        1. 9.5.3.1 Status Byte (STATUS0)
        2. 9.5.3.2 Conversion Data Format
      4. 9.5.4 Cyclic Redundancy Check (CRC)
      5. 9.5.5 Commands
        1. 9.5.5.1  General Command Format
        2. 9.5.5.2  NOP Command
        3. 9.5.5.3  RESET Command
        4. 9.5.5.4  START Command
        5. 9.5.5.5  STOP Command
        6. 9.5.5.6  RDATA Command
        7. 9.5.5.7  OFSCAL Command
        8. 9.5.5.8  GANCAL Command
        9. 9.5.5.9  RREG Command
        10. 9.5.5.10 WREG Command
        11. 9.5.5.11 LOCK Command
        12. 9.5.5.12 UNLOCK Command
    6. 9.6 Register Map
      1. 9.6.1  Device Identification (ID) Register (address = 00h) [reset = 6xh]
        1. Table 30. ID Register Field Descriptions
      2. 9.6.2  Main Status (STATUS0) Register (address = 01h) [reset = 01h]
        1. Table 31. STATUS0 Register Field Descriptions
      3. 9.6.3  Mode 0 (MODE0) Register (address = 02h) [reset = 24h]
        1. Table 32. MODE0 Register Field Descriptions
      4. 9.6.4  Mode 1 (MODE1) Register (address = 03h) [reset = 01h]
        1. Table 33. MODE1 Register Field Descriptions
      5. 9.6.5  Mode 2 (MODE2) Register (address = 04h) [reset = 00h]
        1. Table 34. MODE2 Register Field Descriptions
      6. 9.6.6  Mode 3 (MODE3) Register (address = 05h) [reset = 00h]
        1. Table 35. MODE3 Register Field Descriptions
      7. 9.6.7  Reference Configuration (REF) Register (address = 06h) [reset = 05h]
        1. Table 36. REF Register Field Descriptions
      8. 9.6.8  Offset Calibration (OFCALx) Registers (address = 07h, 08h, 09h) [reset = 00h, 00h, 00h]
        1. Table 37. OFCAL0, OFCAL1, OFCAL2 Registers Field Description
      9. 9.6.9  Full-Scale Calibration (FSCALx) Registers (address = 0Ah, 0Bh, 0Ch) [reset = 00h, 00h, 40h]
        1. Table 38. FSCAL0, FSCAL1, FSCAL2 Registers Field Description
      10. 9.6.10 Current Source Multiplexer (I_MUX) Register (address = 0Dh) [reset = FFh]
        1. Table 39. I_MUX Register Field Descriptions
      11. 9.6.11 Current Source Magnitude (I_MAG) Register (address = 0Eh) [reset = 00h]
        1. Table 40. I_MAG Register Field Descriptions
      12. 9.6.12 Reserved (RESERVED) Register (address = 0Fh) [reset = 00h]
        1. Table 41. RESERVED Register Field Descriptions
      13. 9.6.13 MODE4 (MODE4) Register (address = 10h) [reset = 50h]
        1. Table 42. MODE4 Register Field Descriptions
      14. 9.6.14 PGA Alarm (STATUS1) Register (address = 11h) [reset = xxh]
        1. Table 43. STATUS1 Register Field Descriptions
      15. 9.6.15 Status 2 (STATUS2) Register (address = 12h) [reset = 0xh]
        1. Table 44. STATUS2 Register Field Descriptions
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Input Range
      2. 10.1.2 Input Overload
        1. 10.1.2.1 Input Signal Rate of Change (dV/dt)
      3. 10.1.3 Unused Inputs and Outputs
    2. 10.2 Typical Applications
      1. 10.2.1 ±10-V Analog Input Module
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Thermocouple Input With High Common-Mode Voltage
    3. 10.3 Initialization Setup
  11. 11Power Supply Recommendations
    1. 11.1 Power-Supply Decoupling
    2. 11.2 Analog Power-Supply Clamp
    3. 11.3 Power-Supply Sequencing
    4. 11.4 5-V to ±15-V DC-DC Converter
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.4.1.3 Conversion Latency

The digital filter averages data from the modulator to produce the conversion result. The discrete stages of the digital filter must have settled data to provide fully settled output data. The order and the decimation ratio of the digital filter determine the amount of data averaged that affects the latency of the conversion data. The FIR and sinc1 filter modes are zero latency because the ADC provides the conversion result in one conversion cycle. Latency time is an important consideration for data throughput in multiplexed applications.

Table 8 lists the conversion latency values of the ADC. Conversion latency is defined as the time from the start of the first conversion by taking the START pin high or sending the start command to when the conversion data are ready. The ADC is designed to provide fully settled data under this condition. The conversion latency values listed in Table 8 include the programmable start-conversion delay equal to 50 µs before the digital filter starts, which also includes overhead time for final data processing. After the first conversion completes in continuous conversion mode, the period of the next conversions are equal to 1 / fDATA. The first conversion latency time in auto-zero mode has twice the values listed in Table 8. The values listed in Table 8 are equal to the period of the next conversions.

Table 8. Conversion Latency Time

DATA RATE
(SPS)		 CONVERSION LATENCY TIME (t(STDR)(1), ms)
SINC1 SINC2 SINC3 SINC4 SINC5 FIR
2.5 400.4 800.4 1,200 1,600 — 402.2
5 200.4 400.4 600.4 800.4 — 202.2
10 100.4 200.4 300.4 400.4 — 102.2
16.6 60.43 120.4 180.4 240.4 — —
20 50.43 100.4 150.4 200.4 — 52.22
50 20.43 40.42 60.43 80.43 — —
60 17.09 33.76 50.43 67.09 — —
100 10.43 20.42 30.43 40.43 — —
400 2.925 5.424 7.925 10.43 — —
1200 1.258 2.091 2.925 3.758 — —
2400 0.841 1.258 1.675 2.091 — —
4800 0.633 0.841 1.050 1.258 — —
7200 0.564 0.702 0.841 0.980 — —
14400 — — — — 0.423 —
19200 — — — — 0.336 —
25600 — — — — 0.271 —
40000 — — — — 0.179 —
(1) Auto-zero mode off, conversion-start time delay = 50 µs (DELAY[3:0] = 0001). Actual conversion latency time can vary depending on the accuracy of fCLK.

As shown in Figure 77, if the input signal changes during the conversion phase, the conversion data are a mix of old and new data. After an unsynchronized input change, the number of conversion periods required to provide fully settled output data are calculated by dividing the conversion latency by the nominal period and then adding one additional conversion. In auto-zero mode, use twice the latency values plus one additional conversion.

ADS125H02 ai_freerun_conv_delay_sbas760.gifFigure 77. Input Change During Conversions