SBAS535D August   2013  – June 2026 ADS1120

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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 SPI Timing Requirements
    7. 6.7 SPI Switching Characteristics
    8. 6.8 Timing Diagrams
    9. 6.9 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Noise Performance
  9. 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 PGA
        1. 8.3.2.1 PGA Common-Mode Voltage Requirements
        2. 8.3.2.2 Bypassing the PGA
      3. 8.3.3  Voltage Reference
      4. 8.3.4  Clock Source
      5. 8.3.5  Modulator
      6. 8.3.6  Digital Filter
      7. 8.3.7  Output Data Rate
      8. 8.3.8  Excitation Current Sources
      9. 8.3.9  Low-Side Power Switch
      10. 8.3.10 Sensor Detection
      11. 8.3.11 System Monitor
      12. 8.3.12 Offset Calibration
      13. 8.3.13 Temperature Sensor
        1. 8.3.13.1 Converting From Digital Codes to Temperature
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
      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 Duty-Cycle Mode
        3. 8.4.3.3 Turbo Mode
        4. 8.4.3.4 Power-Down Mode
    5. 8.5 Programming
      1. 8.5.1 Serial Interface
        1. 8.5.1.1 Chip Select (CS)
        2. 8.5.1.2 Serial Clock (SCLK)
        3. 8.5.1.3 Data Ready (DRDY)
        4. 8.5.1.4 Data Input (DIN)
        5. 8.5.1.5 Data Output and Data Ready (DOUT/DRDY)
        6. 8.5.1.6 SPI Timeout
      2. 8.5.2 Data Format
      3. 8.5.3 Commands
        1. 8.5.3.1 RESET (0000 011xb)
        2. 8.5.3.2 START/SYNC (0000 100xb)
        3. 8.5.3.3 POWERDOWN (0000 001xb)
        4. 8.5.3.4 RDATA (0001 xxxxb)
        5. 8.5.3.5 RREG (0010 rrnnb)
        6. 8.5.3.6 WREG (0100 rrnnb)
      4. 8.5.4 Reading Data
      5. 8.5.5 Sending Commands
      6. 8.5.6 Interfacing with Multiple Devices
    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]
        2. 8.6.2.2 Configuration Register 1 (Address = 01h) [reset = 00h]
        3. 8.6.2.3 Configuration Register 2 (Address = 02h) [reset = 00h]
        4. 8.6.2.4 Configuration Register 3 (Address = 03h) [reset = 00h]
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Serial Interface Connections
      2. 9.1.2 Analog Input Filtering
      3. 9.1.3 External Reference and Ratiometric Measurements
      4. 9.1.4 Establishing a Proper Common-Mode 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
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power-Supply Sequencing
      2. 9.3.2 Power-Supply Ramp Rate
      3. 9.3.3 Power-Supply Decoupling
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

8.3.7 Output Data Rate

Table 8-4 shows the actual conversion times for each data rate setting. The values provided are in terms of t(CLK) cycles using an external clock with a clock frequency of fCLK = 4.096MHz. The data rates scale proportionally in case an external clock with a frequency other than 4.096MHz is used.

Continuous-conversion mode data rates are timed from one DRDY falling edge to the next DRDY falling edge. The first conversion starts 210 × tCLK (normal mode, duty-cycle mode) or 114 × tCLK (turbo mode) after the last SCLK falling edge of the START/SYNC command.

Single-shot conversion mode data rates are timed from the last SCLK falling edge of the START/SYNC command to the DRDY falling edge and rounded to the next tCLK. In case the internal oscillator is used, an additional oscillator wake-up time of up to 50µs (normal mode, duty-cycle mode) or 25µs (turbo mode) must be added in single-shot conversion mode. The internal oscillator starts to power up at the first SCLK rising edge of the START/SYNC command. If an SCLK frequency higher than 160kHz (normal mode, duty-cycle mode) or 320kHz (turbo mode) is used, the oscillator can possibly not be fully powered up at the end of the START/SYNC command. The ADC then waits until the internal oscillator is fully powered up before starting a conversion.

Single-shot conversion times in duty-cycle mode are the same as in normal mode. See the Duty-Cycle Mode section for more details on duty-cycle mode operation.

Table 8-4 Conversion Times
NOMINAL DATA RATE
(SPS)		 –3dB BANDWIDTH
(Hz)		 ACTUAL CONVERSION TIME (t(CLK))
CONTINUOUS CONVERSION MODE SINGLE-SHOT CONVERSION MODE
Normal Mode
20 13.1 204768 204850
45 20.0 91120 91218
90 39.6 46128 46226
175 77.8 23664 23762
330 150.1 12464 12562
600 279.0 6896 6994
1000 483.8 4144 4242
Duty-Cycle Mode
5 13.1 823120 n/a
11.25 20.0 364560 n/a
22.5 39.6 184592 n/a
44 77.8 94736 n/a
82.5 150.1 49936 n/a
150 279.0 27664 n/a
250 483.8 16656 n/a
Turbo Mode
40 17.1 102384 102434
90 39.9 45560 45618
180 79.2 23064 23122
350 155.6 11832 11890
660 300.3 6232 6290
1200 558.1 3448 3506
2000 967.6 2072 2130

Even though the conversion time at the 20SPS setting is not exactly 1 / 20Hz = 50ms, this discrepancy does not affect the 50Hz or 60Hz rejection. To achieve the 50Hz and 60Hz rejection specified in the Electrical Characteristics, the external clock frequency must be 4.096MHz. When using the internal oscillator, the conversion time and filter notches vary by the amount specified in the Electrical Characteristics table for oscillator accuracy.