SLASEU7A March   2023  – October 2026 AFE781H1 , AFE881H1

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 One-Time Programmable (OTP) Memory
    4. 6.4 Device Functional Modes
      1. 6.4.1 DAC Power-Down Mode
      2. 6.4.2 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 Serial Peripheral Interface (SPI)
        1. 6.5.2.1 SPI Frame Definition
        2. 6.5.2.2 SPI Read and Write
        3. 6.5.2.3 Frame Error Checking
        4. 6.5.2.4 Synchronization
      3. 6.5.3 UART Interface
        1. 6.5.3.1 UART Break Mode (UBM)
          1. 6.5.3.1.1 Interface With FIFO Buffers and Register Map
      4. 6.5.4 Status Bits
      5. 6.5.5 Watchdog Timer
    6. 6.6 Register Maps
      1. 6.6.1 AFEx81H1 Registers
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Multichannel Configuration
    2. 7.2 Typical Application
      1. 7.2.1 4mA to 20mA Current Transmitter
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Start-Up Circuit
          2. 7.2.1.2.2 Current Loop Control
          3. 7.2.1.2.3 Input Protection and Rectification
          4. 7.2.1.2.4 System Current Budget
        3. 7.2.1.3 Application Curves
    3. 7.3 Initialization Set Up
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.5.1 Layout Guidelines

To maximize the performance of the AFEx81H1 in any application, follow good layout practices and proper circuit design. The following recommendations are specific to the device:

  • For best performance, dedicate an entire PCB layer to a ground plane and do not route any other signal traces on this layer. However, depending on restrictions imposed by specific end equipment, a dedicated ground plane is not always practical. If ground-plane separation is necessary, make a direct connection of the planes at the DAC. Do not connect individual ground planes at multiple locations because this configuration creates ground loops.
  • IOVDD and PVDD must have 100nF decoupling capacitors local to the respective pins. VDD must have at least a 1μF decoupling capacitor used for the internal LDO, or for an external 1.8V supply. Use a high-quality ceramic-type NP0 or X7R capacitor for best performance across temperature and a very low dissipation factor.
  • Place a 100nF reference capacitor close to the VREFIO pin.
  • Avoid routing switching signals near the reference input.
  • Maintain proper placement for the digital and analog sections with respect to the digital and analog components. Separate the analog and digital circuitry for less coupling into neighboring blocks and to minimize the interaction between analog and digital return currents.
  • For designs that include protection circuits:
    • Place diversion elements, such as TVS diodes or capacitors, close to off-board connectors to make sure that return current from high-energy transients does not cause damage to sensitive devices
    • Use large, wide traces to provide a low-impedance path to divert high-energy transients away from the I/O pins.