SLASF44 may   2023 AFE78201 , AFE88201

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: 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  Internal Reference
      6. 7.3.6  Integrated Precision Oscillator
      7. 7.3.7  Precision Oscillator Diagnostics
      8. 7.3.8  One-Time Programmable (OTP) Memory
      9. 7.3.9  GPIO
      10. 7.3.10 Timer
      11. 7.3.11 Unique Chip Identifier (ID)
      12. 7.3.12 Scratch Pad Register
    4. 7.4 Device Functional Modes
      1. 7.4.1 Register Built-In Self-Test (RBIST)
      2. 7.4.2 DAC Power-Down Mode
      3. 7.4.3 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
      2. 7.5.2 GPIO Programming
      3. 7.5.3 Serial Peripheral Interface (SPI)
        1. 7.5.3.1 SPI Frame Definition
        2. 7.5.3.2 SPI Read and Write
        3. 7.5.3.3 Frame Error Checking
        4. 7.5.3.4 Synchronization
      4. 7.5.4 UART Interface
        1. 7.5.4.1 UART Break Mode (UBM)
      5. 7.5.5 Status Bits
      6. 7.5.6 Watchdog Timer
    6. 7.6 Register Maps
      1. 7.6.1 AFEx8201 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 Analog Output Module
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 XTR305
            1. 8.2.1.2.1.1 Current-Output Mode
            2. 8.2.1.2.1.2 Voltage Output Mode
            3. 8.2.1.2.1.3 Diagnostic Features
        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
  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

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7.5.6 Watchdog Timer

The AFEx8201 include a watchdog timer (WDT) that is used to make sure that communication between the system controller and the device is not lost. The WDT checks that the device received a communication from the system controller within a programmable period of time. To enable this feature, set WDT.WDT_EN to 1. The WDT monitors both SPI and UBM communications.

The WDT has two limit fields: WDT.WDT_UP and WDT.WDT_LO. The WDT_UP field sets the upper time limit for the WDT. The WDT_LO field sets the lower time limit. If the WDT_LO is set to a value other than 2’b00, then the WDT acts as a window comparator. If the write occurs too quickly (less than the WDT_LO time), or too slowly (greater than the WDT_UP time), then a WDT error is asserted. When acting as a window comparator, in the event of a WDT error, the WDT resets only when a write to the WDT register occurs. If the WDT_LO is set to 2'b00, then a write to any register resets the WDT time counter. In this mode, the WDT error is asserted when the timer expires.

If enabled, the chip must have any SPI or UBM write to the device within the programmed timeout window. Otherwise, the ALARM pin asserts low, and the ALARM_STATUS.WD_FLT bit is set to 1. The WD_FLT bit is sticky. After a WD_FLT has been asserted, WDT.WDT_EN must be set to 0 to clear the WDT condition. Then the WDT can be re-enabled. The WDT condition is also cleared by issuing a software or hardware reset. After the WDT condition is clear, WD_FLT is cleared by reading the ALARM_STATUS register.

When using multiple AFEx8201 devices in a daisy-chain configuration, connect the open-drain ALARM pins of all devices together to form a wired-OR network. The watchdog timer can be enabled in any number of the devices in the chain; although, enabling the watchdog timer in one device in the chain is usually sufficient. The wired-OR ALARM pin can be pulled low in response to the simultaneous presence of different trigger conditions in the devices in the daisy-chain. The host processor must read the ALARM_STATUS register of each device to know all the fault conditions present in the chain.

The watchdog timeout period is based on a 1200-Hz clock (1.2288 MHz / 1024).