SLASF43A December   2023  â€“ September 2026 AFE782H1 , AFE882H1

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  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics
    6. 5.6  Timing Requirements
    7. 5.7  Timing Diagrams
    8. 5.8  Typical Characteristics: VOUT DAC
    9. 5.9  Typical Characteristics: ADC
    10. 5.10 Typical Characteristics: Reference
    11. 5.11 Typical Characteristics: HART Modem
    12. 5.12 Typical Characteristics: Power Supply
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Digital-to-Analog Converter (DAC) Overview
        1. 6.3.1.1 DAC Resistor String
        2. 6.3.1.2 DAC Buffer Amplifier
        3. 6.3.1.3 DAC Transfer Function
        4. 6.3.1.4 DAC Gain and Offset Calibration
        5. 6.3.1.5 Programmable Slew Rate
        6. 6.3.1.6 DAC Register Structure and CLEAR State
      2. 6.3.2  Analog-to-Digital Converter (ADC) Overview
        1. 6.3.2.1 ADC Operation
        2. 6.3.2.2 ADC Custom Channel Sequencer
        3. 6.3.2.3 ADC Synchronization
        4. 6.3.2.4 ADC Offset Calibration
        5. 6.3.2.5 External Monitoring Inputs
        6. 6.3.2.6 Temperature Sensor
        7. 6.3.2.7 Self-Diagnostic Multiplexer
        8. 6.3.2.8 ADC Bypass
      3. 6.3.3  Programmable Out-of-Range Alarms
        1. 6.3.3.1 Alarm-Based Interrupts
        2. 6.3.3.2 Alarm Action Configuration Register
        3. 6.3.3.3 Alarm Voltage Generator
        4. 6.3.3.4 Temperature Sensor Alarm Function
        5. 6.3.3.5 Internal Reference Alarm Function
        6. 6.3.3.6 ADC Alarm Function
        7. 6.3.3.7 Fault Detection
      4. 6.3.4  IRQ
      5. 6.3.5  HART Interface
        1. 6.3.5.1  FIFO Buffers
          1. 6.3.5.1.1 FIFO Buffer Access
          2. 6.3.5.1.2 FIFO Buffer Flags
        2. 6.3.5.2  HART Modulator
        3. 6.3.5.3  HART Demodulator
        4. 6.3.5.4  HART Modem Modes
          1. 6.3.5.4.1 Half-Duplex Mode
          2. 6.3.5.4.2 Full-Duplex Mode
        5. 6.3.5.5  HART Modulation and Demodulation Arbitration
          1. 6.3.5.5.1 HART Receive Mode
          2. 6.3.5.5.2 HART Transmit Mode
        6. 6.3.5.6  HART Modulator Timing and Preamble Requirements
        7. 6.3.5.7  HART Demodulator Timing and Preamble Requirements
        8. 6.3.5.8  IRQ Configuration for HART Communication
        9. 6.3.5.9  HART Communication Using the SPI
        10. 6.3.5.10 HART Communication Using UART
        11. 6.3.5.11 Memory Built-In Self-Test (MBIST)
      6. 6.3.6  Internal Reference
      7. 6.3.7  Integrated Precision Oscillator
      8. 6.3.8  Precision Oscillator Diagnostics
      9. 6.3.9  One-Time Programmable (OTP) Memory
      10. 6.3.10 GPIO
      11. 6.3.11 Timer
      12. 6.3.12 Unique Chip Identifier (ID)
      13. 6.3.13 Scratch Pad Register
    4. 6.4 Device Functional Modes
      1. 6.4.1 DAC Power-Down Mode
      2. 6.4.2 Register Built-In Self-Test (RBIST)
      3. 6.4.3 Reset
    5. 6.5 Programming
      1. 6.5.1 Communication Setup
        1. 6.5.1.1 SPI Mode
        2. 6.5.1.2 UART Mode
        3. 6.5.1.3 SPI Plus UART Mode
        4. 6.5.1.4 HART Functionality Setup Options
      2. 6.5.2 GPIO Programming
      3. 6.5.3 Serial Peripheral Interface (SPI)
        1. 6.5.3.1 SPI Frame Definition
        2. 6.5.3.2 SPI Read and Write
        3. 6.5.3.3 Frame Error Checking
        4. 6.5.3.4 Synchronization
      4. 6.5.4 UART Interface
        1. 6.5.4.1 UART Break Mode (UBM)
          1. 6.5.4.1.1 Interface With FIFO Buffers and Register Map
      5. 6.5.5 Status Bits
      6. 6.5.6 Watchdog Timer
  8. 7 Register Maps
    1. 7.1 AFEx82H1 Registers
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Multichannel Configuration
    2. 8.2 Typical Application
      1. 8.2.1 4mA to 20mA Current Transmitter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Current Loop Control
          2. 8.2.1.2.2 HART Connections
          3. 8.2.1.2.3 Input Protection and Rectification
          4. 8.2.1.2.4 System Current Budget
        3. 8.2.1.3 Application Curves
    3. 8.3 Initialization Setup
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 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

8.2.1.2 Detailed Design Procedure

Figure 8-3 shows a block diagram of a loop-powered, 4mA to 20mA current transmitter.

AFE782H1 AFE882H1 Block Diagram of a Loop-Powered, 4mA to 20mA Current Transmitter Figure 8-3 Block Diagram of a Loop-Powered, 4mA to 20mA Current Transmitter

The terminals connected to the loop are shown on the right side of the block diagram. This connection to the loop powers the entire transmitter. A bridge rectifier at the input protects against reverse connection to the loop. The rectified loop voltage powers a start-up circuit that provides power to an LDO, that in turn powers the AFE882H1 and an MCU.

The AFE882H1 controls the loop current through the voltage-to-current (V-to-I) converter block. The DAC voltage sets the output from 0V to 2.5V. The output is sent through a V-to-I converter block using an OPA333 and an NPN bipolar junction transistor (BJT).

The HART signal is not received at the positive terminal of the 4mA to 20mA connections, but instead is received after the loop-protection rectifier. This HART signal input is capacitively coupled to this LOOP+ internal node of the circuit as shown in Figure 8-2. The HART signal output is modulated onto the loop current from the AFE882H1 through the V-to-I converter circuit.