SLASEU7 March   2023 AFE781H1 , AFE881H1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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  Timing Requirements
    7. 6.7  Timing Diagrams
    8. 6.8  Typical Characteristics: VOUT DAC
    9. 6.9  Typical Characteristics: ADC
    10. 6.10 Typical Characteristics: Reference
    11. 6.11 Typical Characteristics: HART Modem
    12. 6.12 Typical Characteristics: Power Supply
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Digital-to-Analog Converter (DAC) Overview
        1. 7.3.1.1 DAC Resistor String
        2. 7.3.1.2 DAC Buffer Amplifier
        3. 7.3.1.3 DAC Transfer Function
        4. 7.3.1.4 DAC Gain and Offset Calibration
        5. 7.3.1.5 Programmable Slew Rate
        6. 7.3.1.6 DAC Register Structure and CLEAR State
      2. 7.3.2 Analog-to-Digital Converter (ADC) Overview
        1. 7.3.2.1 ADC Operation
        2. 7.3.2.2 ADC Custom Channel Sequencer
        3. 7.3.2.3 ADC Synchronization
        4. 7.3.2.4 ADC Offset Calibration
        5. 7.3.2.5 External Monitoring Inputs
        6. 7.3.2.6 Temperature Sensor
        7. 7.3.2.7 Self-Diagnostic Multiplexer
        8. 7.3.2.8 ADC Bypass
      3. 7.3.3 Programmable Out-of-Range Alarms
        1. 7.3.3.1 Alarm-Based Interrupts
        2. 7.3.3.2 Alarm Action Configuration Register
        3. 7.3.3.3 Alarm Voltage Generator
        4. 7.3.3.4 Temperature Sensor Alarm Function
        5. 7.3.3.5 Internal Reference Alarm Function
        6. 7.3.3.6 ADC Alarm Function
        7. 7.3.3.7 Fault Detection
      4. 7.3.4 IRQ
      5. 7.3.5 HART Interface
        1. 7.3.5.1  FIFO Buffers
          1. 7.3.5.1.1 FIFO Buffer Access
          2. 7.3.5.1.2 FIFO Buffer Flags
        2. 7.3.5.2  HART Modulator
        3. 7.3.5.3  HART Demodulator
        4. 7.3.5.4  HART Modem Modes
          1. 7.3.5.4.1 Half-Duplex Mode
          2. 7.3.5.4.2 Full-Duplex Mode
        5. 7.3.5.5  HART Modulation and Demodulation Arbitration
          1. 7.3.5.5.1 HART Receive Mode
          2. 7.3.5.5.2 HART Transmit Mode
        6. 7.3.5.6  HART Modulator Timing and Preamble Requirements
        7. 7.3.5.7  HART Demodulator Timing and Preamble Requirements
        8. 7.3.5.8  IRQ Configuration for HART Communication
        9. 7.3.5.9  HART Communication Using the SPI
        10. 7.3.5.10 HART Communication Using UART
        11. 7.3.5.11 Memory Built-In Self-Test (MBIST)
      6. 7.3.6 Internal Reference
      7. 7.3.7 Integrated Precision Oscillator
      8. 7.3.8 One-Time Programmable (OTP) Memory
    4. 7.4 Device Functional Modes
      1. 7.4.1 DAC Power-Down Mode
      2. 7.4.2 Reset
    5. 7.5 Programming
      1. 7.5.1 Communication Setup
        1. 7.5.1.1 SPI Mode
        2. 7.5.1.2 UART Mode
        3. 7.5.1.3 SPI Plus UART Mode
        4. 7.5.1.4 HART Functionality Setup Options
      2. 7.5.2 Serial Peripheral Interface (SPI)
        1. 7.5.2.1 SPI Frame Definition
        2. 7.5.2.2 SPI Read and Write
        3. 7.5.2.3 Frame Error Checking
        4. 7.5.2.4 Synchronization
      3. 7.5.3 UART Interface
        1. 7.5.3.1 UART Break Mode (UBM)
          1. 7.5.3.1.1 Interface With FIFO Buffers and Register Map
      4. 7.5.4 Status Bits
      5. 7.5.5 Watchdog Timer
    6. 7.6 Register Maps
      1. 7.6.1 AFEx81H1 Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Multichannel Configuration
    2. 8.2 Typical Application
      1. 8.2.1 4-mA to 20-mA Current Transmitter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Start-Up Circuit
          2. 8.2.1.2.2 Current Loop Control
          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 Set Up
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  9. 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
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.5.1 FIFO Buffers

First-in, first-out (FIFO) buffers are used to transmit and receive HART data using both the SPI and UART. Both the transmit FIFO (FIFO_U2H) and receive FIFO (FIFO_H2U) buffers are 32 rows and 9-bits wide. The 9-bit width allows the storage of the parity bit with the data byte. Bit[8] is the parity bit as received by either the UART or HART demodulator, depending on the direction of the data flow. The device does not calculate the parity bit in this case, and transmits the data with the wrong parity bit if the wrong parity bit was received. Bits[7:0] are the data.

The AFEx81H1 HART implementation is shown in Figure 7-17.

Figure 7-17 HART Architecture

HART data bytes are enqueued into a transmit FIFO_U2H buffer using the SPI or UART. The input data bits are translated into the mark (1200 Hz) and space (2200 Hz) FSK analog signals (see Figure 7-16) used in HART communication by the internal HART transmit modulator. The receive demodulator enqueues HART data into the receive FIFO_H2U buffer. An arbiter is implemented with signals to CD and from the RTS pins to manage the HART physical connections on MOD_OUT, and either the RX_IN or RX_INF pin. To enable efficient and error free communication, the arbiter in conjunction with the two FIFO buffers can be used to produce an IRQ for the system controller.