SLVSFF0B June   2020  – July 2022 DRV8436E

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
    1.     Device Options
  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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 PWM Motor Drivers
      2. 7.3.2 Bridge Control
      3. 7.3.3 Current Regulation
      4. 7.3.4 Decay Modes
        1. 7.3.4.1 Slow Decay
        2. 7.3.4.2 Mixed Decay
        3. 7.3.4.3 Fast Decay
        4. 7.3.4.4 Smart tune Dynamic Decay
        5. 7.3.4.5 Blanking time
      5. 7.3.5 Charge Pump
      6. 7.3.6 Linear Voltage Regulators
      7. 7.3.7 Logic and Quad-Level Pin Diagrams
        1. 7.3.7.1 nFAULT Pin
      8. 7.3.8 Protection Circuits
        1. 7.3.8.1 VM Undervoltage Lockout (UVLO)
        2. 7.3.8.2 VCP Undervoltage Lockout (CPUV)
        3. 7.3.8.3 Overcurrent Protection (OCP)
        4. 7.3.8.4 Thermal Shutdown (OTSD)
        5. 7.3.8.5 36
    4. 7.4 Device Functional Modes
      1. 7.4.1 Sleep Mode (nSLEEP = 0)
      2. 7.4.2 Operating Mode (nSLEEP = 1)
      3. 7.4.3 Functional Modes Summary
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Primary Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Current Regulation
    3. 8.3 Typical Application
      1. 8.3.1 Design Requirements
      2. 8.3.2 Detailed Design Procedure
        1. 8.3.2.1 Current Regulation
        2. 8.3.2.2 Stepper Motor Speed
        3. 8.3.2.3 Decay Modes
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
  12. 12Mechanical, Packaging, and Orderable Information

7.3.3 Current Regulation

The current through the motor windings is regulated by an adjustable, off-time PWM current-regulation circuit. When an H-bridge is enabled, current rises through the winding at a rate dependent on the DC voltage, inductance of the winding, and the magnitude of the back EMF present. When the current hits the current regulation threshold, the bridge enters a decay mode for a period of time determined by the TOFF pin setting to decrease the current. After the off-time expires, the bridge is re-enabled, starting another PWM cycle.

Table 7-4 Off-Time Settings
TOFF OFF-TIME tOFF
0 7 µs
1 16 µs
Hi-Z 24 µs
330kΩ to GND 32 µs

The PWM chopping current is set by a comparator which monitors the voltage across the current sense MOSFETs in parallel with the low-side power MOSFETs. To generate the reference voltage for the current chopping comparator, the VREFx input is attenuated by a factor of Kv.

The chopping current (IFS) can be calculated as IFS (A) = VREFx (V) / KV (V/A) = VREFx (V) / 2.2 (V/A).