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

7.3.1.6 DAC Register Structure and CLEAR State

The AFE881H1 DAC has a 16-bit voltage output, and the AFE781H1 DAC has a 14-bit voltage output. Table 7-1 shows four possible VOUT DAC output ranges. With a voltage-to-current converter stage, the narrow range corresponds to a 4-mA to 20-mA range. The full range allows for undercurrents and overcurrents from 3 mA to 25 mA, and is controlled by DAC_CFG.RANGE.

The AFEx81H1 provide the option to quickly set the DAC output to the value set in the DAC_CLR_CODE register without writing to the DAC_DATA register, referred to as the CLEAR state. Setting the DAC to CLEAR state also sets the DAC output range according to DAC_CFG.CLR_RANGE. For register details, see Table 7-18.

Transitioning from the DAC_DATA to the DAC_CLR_CODE is synchronous to the clock. If slew mode is enabled, the output slews during the transition. Figure 7-7 shows the full AFEx81H1 DAC_DATA signal path. The devices synchronize the DAC_DATA code to the internal clock, causing up to 2.5 internal clock cycles of latency (2 μs) with respect to the rising edge of CS or the end of a UBM command. Update DAC_GAIN and DAC_OFFSET values when DAC_CFG.SR_EN = 0 to avoid an IRQ pulse generated by SR_BUSY.

Set the DAC to CLEAR state either by:

  1. Setting DAC_CFG.CLR.
  2. Configuring the DAC to transition to the CLEAR state in response to an alarm condition.
  3. Using the SDI pin in UBM as the CLEAR state input pin.

Method 1 is a direct command to the AFEx81H1 to set the DAC to CLEAR state. Set the DAC_CFG.CLR bit to 1h to set the DAC to CLEAR state.

Method 2 is controlled by settings of ALARM_ACT register. For details of conditions and other masks required to use this method, see Table 7-29 and Section 7.3.3.2.

Method 3 supports setting the DAC to CLEAR state without writing to the AFEx81H1. This pin-based DAC CLEAR state function is available only in UBM on the SDI pin. For details of connection options based on communication modes and pins used in each mode, see Section 7.5.1. Set the appropriate pin high to drive the DAC to CLEAR state.

Figure 7-7 DAC Data Path