SLASEJ4C April   2017  – February 2023 PGA460

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  Internal Supply Regulators Characteristics
    6. 6.6  Transducer Driver Characteristics
    7. 6.7  Transducer Receiver Characteristics
    8. 6.8  Analog to Digital Converter Characteristics
    9. 6.9  Digital Signal Processing Characteristics
    10. 6.10 Temperature Sensor Characteristics
    11. 6.11 High-Voltage I/O Characteristics
    12. 6.12 Digital I/O Characteristics
    13. 6.13 EEPROM Characteristics
    14. 6.14 Timing Requirements
    15. 6.15 Switching Characteristics
    16. 6.16 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Power-Supply Block
      2. 7.3.2  Burst Generation
        1. 7.3.2.1 Using Center-Tap Transformer
        2. 7.3.2.2 Direct Drive
        3. 7.3.2.3 Other Configurations
      3. 7.3.3  Analog Front-End
      4. 7.3.4  Digital Signal Processing
        1. 7.3.4.1 Ultrasonic Echo—Band-Pass Filter
        2. 7.3.4.2 Ultrasonic Echo–Rectifier, Peak Hold, Low-Pass Filter, and Data Selection
        3. 7.3.4.3 Ultrasonic Echo—Nonlinear Scaling
        4. 7.3.4.4 Ultrasonic Echo—Threshold Data Assignment
        5. 7.3.4.5 Digital Gain
      5. 7.3.5  System Diagnostics
        1. 7.3.5.1 Device Internal Diagnostics
      6. 7.3.6  Interface Description
        1. 7.3.6.1 Time-Command Interface
          1. 7.3.6.1.1 RUN Commands
          2. 7.3.6.1.2 CONFIGURATION/STATUS Command
        2. 7.3.6.2 USART Interface
          1. 7.3.6.2.1 USART Asynchronous Mode
            1. 7.3.6.2.1.1 Sync Field
            2. 7.3.6.2.1.2 Command Field
            3. 7.3.6.2.1.3 Data Fields
            4. 7.3.6.2.1.4 Checksum Field
            5. 7.3.6.2.1.5 PGA460 UART Commands
            6. 7.3.6.2.1.6 UART Operations
              1. 7.3.6.2.1.6.1 No-Response Operation
              2. 7.3.6.2.1.6.2 Response Operation (All Except Register Read)
              3. 7.3.6.2.1.6.3 Response Operation (Register Read)
            7. 7.3.6.2.1.7 Diagnostic Field
            8. 7.3.6.2.1.8 USART Synchronous Mode
          2. 7.3.6.2.2 One-Wire UART Interface
          3. 7.3.6.2.3 Ultrasonic Object Detection Through UART Operations
        3. 7.3.6.3 In-System IO-Pin Interface Selection
      7. 7.3.7  Echo Data Dump
        1. 7.3.7.1 On-Board Memory Data Store
        2. 7.3.7.2 Direct Data Burst Through USART Synchronous Mode
      8. 7.3.8  Low-Power Mode
        1. 7.3.8.1 Time-Command Interface
        2. 7.3.8.2 UART Interface
      9. 7.3.9  Transducer Time and Temperature Decoupling
        1. 7.3.9.1 Time Decoupling
        2. 7.3.9.2 Temperature Decoupling
      10. 7.3.10 Memory CRC Calculation
      11. 7.3.11 Temperature Sensor and Temperature Data-Path
      12. 7.3.12 TEST Pin Functionality
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 UART and USART Communication Examples
    6. 7.6 Register Maps
      1. 7.6.1 EEPROM Programming
      2. 7.6.2 Register Map Partitioning and Default Values
      3. 7.6.3 REGMAP Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Transducer Types
    2. 8.2 Typical Applications
      1. 8.2.1 Transformer-Driven Method
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Transducer Driving Voltage
          2. 8.2.1.2.2 Transducer Driving Frequency
          3. 8.2.1.2.3 Transducer Pulse Count
          4. 8.2.1.2.4 Transformer Turns Ratio
          5. 8.2.1.2.5 Transformer Saturation Current and Main Voltage Rating
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Direct-Driven (Transformer-Less) Method
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 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
7.3.6.1.1 RUN Commands

The run commands are used for device run-time operation and are most commonly used during the normal operation cycle of the PGA460 device. These device commands are specified by pulling the IO pull low for a specified period of time as defined in the GUID-6906D0A9-86EC-46B1-B4A5-F88035F60F0B.html#TITLE-SLASEC8TOCWRAPPER_SPECIFICATIONS section. The following are classified as run commands:

    Burst/Listen (Preset1)The device sends an ultrasonic burst using the P1_PULSE number of pulses while using the CURR_LIM1 current-limit setting and runs an object-detection record interval defined by the value of the P1_REC time length. During the process of object detection, the P1_THR_xx threshold map is used for signal comparison. The nonlinear scaling DSP function is available for use with this command.
    Burst/Listen (Preset2)The device sends an ultrasonic burst using the P2_PULSE number of pulses while using the CURR_LIM2 current-limit setting and runs an object-detection record interval defined by the value of the P2_REC time length. During the process of object detection, the P2_THR_xx threshold map is used for signal comparison. The nonlinear scaling DSP function is available for use with this command.
    Listen Only (Preset1)The device does not send an ultrasonic burst, however, and only runs an object-detection record interval defined by the value of the P1_REC time length. During the process of object detection, the P1_THR_xx threshold map is used for signal comparison. The nonlinear scaling DSP function is available for use with this command.
    Listen Only (Preset2)The device does not send an ultrasonic burst, however, but only runs an object-detection record interval defined by the value of the P2_REC time length. During the process of object detection, the P2_THR_xx threshold map is used for signal comparison. The nonlinear scaling DSP function is available for use with this command.

#X5872 shows the process of the communication of the IO pin run command.

Figure 7-12 Time-Command Interface RUN Command Execution

The status field of the PGA460 device is embedded in the run command and provided back to the controller by extending the dead-time on the IO bus. The dead-time can be further extended for up to 3 × t(DT_TCI) which signifies three status bits, STAT[1:3]. Table 7-1 shows the assigned diagnostic and a priority of each status bit.

Table 7-1 Time-Command Interface Status Bits Description
STATUS BITPRIORITYDESCRIPTION
STAT 11, lowThreshold settings uninitialized error
STAT 22Frequency diagnostics error
Voltage diagnostic error
STAT 33, highPower-up auto EEPROM CRC error
User triggered EEPROM download CRC error

As listed in Table 7-1, the STAT3 bit has the highest priority. When a STAT3 error condition is present, then the dead-time is further extended by 3 × t(DT_TCI). In this case, if any STAT2 or STAT1 error conditions are also present, these conditions are overruled by the higher priority of STAT3 error conditions. In a similar way, a STAT1 condition is overruled by a STAT2 error condition in which case the dead-time is further extended by 2 × t(DT_TCI). When all STAT3 and STAT2 error conditions have cleared, a STAT1 condition further extends the dead-time by an additional t(DT_TCI).

The functions of the status bits can be explained as follows:

    STAT 1This status bit is set to 1 when both preset threshold register groups are uninitialized. Any run command received over the TCI communications channel is not executed until either preset threshold register group is programmed.
    STAT 3Any run command received over the TCI communications channel is not executed until the EE CRC error is fixed.

    The user can write to any EEPROM-mapped register to clear the error.

    The user must reprogram the EEPROM to prevent the error upon another automatically or manually triggered EEPROM download operation.

When the device receives a run command, the IO pin is actively driven by the PGA460 device depending on the final DSP output to indicate object detection. If, at any time, the processed echo signal exceeds the threshold at that time, the IO pin is pulled low (GND, strong pulldown) otherwise the IO pin is pulled up by the internal 10-kΩ (weak pullup) resistor. When the record time reaches the end of the record defined by the Px_REC parameters, the IO pin is released (pulled up as an input) and the device is ready for a next command. #X4572 shows the object detection functionality of the IO pin. The device pulls the IO pin low during the burst and then releases it to provide a reference for the recording time-frame for the MCU. Knowing the time of reference, the duration of the programmed burst and following falling edges for each object detected, the controller or MCU can calculate the object distance.

GUID-6C6019F9-79F5-4AC5-B8D0-8F67BAB94445-low.gifFigure 7-13 IO-Pin Object-Detection Signaling With Burst/Listen Time Command
GUID-347E8830-6837-4959-9D03-6D9A288EA788-low.gifFigure 7-14 IO-Pin Object-Detection Signaling With Listen-Only Time Command

The PGA460 device forces IO pin to go low after the t(DT_TCI) time passes after receiving a run command for a minimum of 300 µs which indicates start of the record period. This process occurs to provide the controller a reference edge to start the time of flight measurement and also for PGA460 device to separate the response of the status (STAT) bits from the record cycle information. In general, the duration of burst for lower frequency range followed by ringing causes the AFE to saturate and pull the IO pin low for more than 300 µs. For higher frequency burst or for listen-only command, or in situations where the saturation caused by the ultrasonic burst might not be a higher value than the assigned threshold (see #X7681), the minimum pulse width is 300 µs. With a certain filter and deglitch setting, a fake object can be detected directly after this 300-µs period.