SLVSH86A December   2023  – June 2024 MCT8314Z

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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 SPI Timing Requirements
    7. 6.7 SPI Secondary Device Mode Timings
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Output Stage
      2. 7.3.2  PWM Control Mode (1x PWM Mode)
        1. 7.3.2.1 Analog Hall Input Configuration
        2. 7.3.2.2 Digital Hall Input Configuration
        3. 7.3.2.3 Asynchronous Modulation
        4. 7.3.2.4 Synchronous Modulation
        5. 7.3.2.5 Motor Operation
      3. 7.3.3  Device Interface Modes
        1. 7.3.3.1 Serial Peripheral Interface (SPI)
        2. 7.3.3.2 Hardware Interface
      4. 7.3.4  AVDD Linear Voltage Regulator
      5. 7.3.5  Charge Pump
      6. 7.3.6  Slew Rate
      7. 7.3.7  Cross Conduction (Dead Time)
      8. 7.3.8  Propagation Delay
      9. 7.3.9  Pin Diagrams
        1. 7.3.9.1 Logic Level Input Pin (Internal Pulldown)
        2. 7.3.9.2 Logic Level Input Pin (Internal Pullup)
        3. 7.3.9.3 Open Drain Pin
        4. 7.3.9.4 Push Pull Pin
        5. 7.3.9.5 Seven Level Input Pin
      10. 7.3.10 Automatic Synchronous Rectification Mode (ASR Mode)
      11. 7.3.11 Cycle-by-Cycle Current Limit
        1. 7.3.11.1 Cycle by Cycle Current Limit with 100% Duty Cycle Input
      12. 7.3.12 Hall Comparators (Analog Hall Inputs)
      13. 7.3.13 Advance Angle
      14. 7.3.14 FG Signal
      15. 7.3.15 Protections
        1. 7.3.15.1 VM Supply Undervoltage Lockout (NPOR)
        2. 7.3.15.2 AVDD Undervoltage Lockout (AVDD_UV)
        3. 7.3.15.3 VCP Charge Pump Undervoltage Lockout (CPUV)
        4. 7.3.15.4 Overvoltage Protections (OVP)
        5. 7.3.15.5 Overcurrent Protection (OCP)
          1. 7.3.15.5.1 OCP Latched Shutdown (OCP_MODE = 00b or MCT8314ZH)
          2. 7.3.15.5.2 OCP Automatic Retry (OCP_MODE = 01b)
          3. 7.3.15.5.3 OCP Report Only (OCP_MODE = 10b)
          4. 7.3.15.5.4 OCP Disabled (OCP_MODE = 11b)
        6. 7.3.15.6 Motor Lock (MTR_LOCK)
          1. 7.3.15.6.1 MTR_LOCK Latched Shutdown (MTR_LOCK_MODE = 00b)
          2. 7.3.15.6.2 MTR_LOCK Automatic Retry (MTR_LOCK_MODE = 01b or MCT8314ZH)
          3. 7.3.15.6.3 MTR_LOCK Report Only (MTR_LOCK_MODE= 10b)
          4. 7.3.15.6.4 MTR_LOCK Disabled (MTR_LOCK_MODE = 11b)
        7. 7.3.15.7 Thermal Warning (OTW)
        8. 7.3.15.8 Thermal Shutdown (OTS)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Functional Modes
        1. 7.4.1.1 Sleep Mode
        2. 7.4.1.2 Operating Mode
        3. 7.4.1.3 Fault Reset (CLR_FLT or nSLEEP Reset Pulse)
    5. 7.5 SPI Communication
      1. 7.5.1 Programming
        1. 7.5.1.1 SPI Format
  9. 8 Register Map
    1. 8.1 STATUS Registers
    2. 8.2 CONTROL Registers
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Hall Sensor Configuration and Connection
      1. 9.2.1 Typical Configuration
      2. 9.2.2 Open Drain Configuration
      3. 9.2.3 Series Configuration
      4. 9.2.4 Parallel Configuration
    3. 9.3 Typical Applications
      1. 9.3.1 Three-Phase Brushless-DC Motor Control With Current Limit
        1. 9.3.1.1 Detailed Design Procedure
          1. 9.3.1.1.1 Motor Voltage
          2. 9.3.1.1.2 Using Automatic Synchronous Rectification Mode (ASR Mode)
          3. 9.3.1.1.3 Power Dissipation and Junction Temperature Losses
        2. 9.3.1.2 Application Curves
    4. 9.4 Power Supply Recommendations
      1. 9.4.1 Bulk Capacitance
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
      2. 9.5.2 Layout Example
      3. 9.5.3 Thermal Considerations
        1. 9.5.3.1 Power Dissipation
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Package Option Addendum
    2. 12.2 Tape and Reel Information

7.3.10 Automatic Synchronous Rectification Mode (ASR Mode)

The automatic synchronous rectification (ASR) mode in the MCT8314Z decreases power losses and thermal dissipation by reducing diode conduction losses in the low-side MOSFET. When this feature is enabled, the device automatically turns ON the low-side MOSFET during the PWM OFF time regardless of the device modulation setting. During the PWM OFF time, if the current drops to 0 A, the device automatically disables the MOSFET to avoid back EMF generating negative current in the motor windings. This negative current creates a negative torque on the BLDC motor, and it can reduce performance of low-inductance motors. When ASR mode is enabled, the current during the decay is monitored and the low-side FET is turned off as soon as the current reaches near to zero. This saves the negative current building in the BLDC motor which results in better noise performance and better thermal management. Figure 7-19 and Figure 7-20 compare asynchronous and synchronous PWM modes with ASR.

MCT8314Z Comparing Asynchronous Modulation and ASRFigure 7-19 Comparing Asynchronous Modulation and ASR
MCT8314Z Comparing Synchronous Modulation and ASRFigure 7-20 Comparing Synchronous Modulation and ASR

The MCT8314Z device includes a low-side (ASR_LS) comparator which detects the negative flow of current in the device on each low-side MOSFET. The ASR_LS comparator compares the sense-FET output with the ground (0-V) threshold. When the current flows from PGND to OUTx, the ASR_LS comparator trips. This comparator provides a reference point for the operation of the ASR feature.

MCT8314Z ASR Operation Figure 7-21 ASR Operation

In the SPI device variant, the EN_ASR bit configures active demagnetization. In the hardware variant, the MODE pin configures active demagnetization as shown in Table 7-5.

Table 7-5 PWM_MODE Configuration
MODE Type MODE Pin (Hardware Variant) Hall Configuration Modulation ASR configuration ASR Mode
Mode 1 Connected to AGND Analog Hall Input Asynchronous EN_ASR = 0 ASR Disabled
Mode 2 Connected to AGND with RMODE1 Digital Hall Input
Mode 3 Connected to AGND with RMODE2 Analog Hall Input Synchronous
Mode 4 Hi-Z Digital Hall Input
Mode 5 Connected to AVDD with RMODE2 Analog Hall Input EN_ASR = 1 ASR Enabled
Mode 6 Connected to AVDD with RMODE1 Digital Hall Input
Mode 7 Connected to AVDD

This device does not support smart rectification through the high-side MOSFET. Currents returning to the VM will flow through the high-side body diodes.