SLVSC40H June   2013  – May 2020 DRV8711

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 SPI Timing Requirements
    7. 6.7 Indexer Timing Requirements
    8. 6.8 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  PWM Motor Drivers
      2. 7.3.2  Direct PWM Input Mode
      3. 7.3.3  Microstepping Indexer
      4. 7.3.4  Current Regulation
      5. 7.3.5  Decay Modes
      6. 7.3.6  Blanking Time
      7. 7.3.7  Predrivers
      8. 7.3.8  Configuring Predrivers
      9. 7.3.9  External FET Selection
      10. 7.3.10 Stall Detection
        1. 7.3.10.1 Internal Stall Detection
        2. 7.3.10.2 External Stall Detection
      11. 7.3.11 Protection Circuits
        1. 7.3.11.1 Overcurrent Protection (OCP)
        2. 7.3.11.2 Predriver Fault
        3. 7.3.11.3 Thermal Shutdown (TSD)
        4. 7.3.11.4 Undervoltage Lockout (UVLO)
    4. 7.4 Device Functional Modes
      1. 7.4.1 RESET and SLEEPn Operation
      2. 7.4.2 Microstepping Drive Current
    5. 7.5 Programming
      1. 7.5.1 Serial Data Format
    6. 7.6 Register Maps
      1. 7.6.1 Control Registers
      2. 7.6.2 CTRL Register (Address = 0x00)
      3. 7.6.3 TORQUE Register (Address = 0x01)
      4. 7.6.4 OFF Register (Address = 0x02)
      5. 7.6.5 BLANK Register (Address = 0x03)
      6. 7.6.6 DECAY Register (Address = 0x04)
      7. 7.6.7 STALL Register (Address = 0x05)
      8. 7.6.8 DRIVE Register (Address = 0x06)
      9. 7.6.9 STATUS Register (Address = 0x07)
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Sense Resistor
      2. 8.1.2 Optional Series Gate Resistor
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Set Step Rate
        2. 8.2.2.2 Calculate Current Regulation
        3. 8.2.2.3 Support External FETs
        4. 8.2.2.4 Pick Decay Mode
        5. 8.2.2.5 Config Stall Detection
        6. 8.2.2.6 Application Curves
  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 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.2.2 Calculate Current Regulation

In a stepper motor, the set full-scale current (IFS) is the maximum current driven through either winding. For the DRV8711, this quantity will depend on the analog voltage, the programmed torque and gain values, and the sense resistor value (RSENSE). During stepping, IFS defines the current chopping threshold (ITRIP) for the maximum current step. The gain of DRV8711 is set for 5 V/V.

Equation 7. DRV8711 equation_03_slvsc40.gif

To achieve IFS = 1.25 A with RSENSE of 0.2 Ω with a gain of 5, TORQUE should be set to 116(dec).

IFS is set by a comparator which compares the voltage across RSENSE to a reference voltage. There is a current sense amplifier built in with programmable gain through ISGAIN. Note that IFS must also follow Equation 8 in order to avoid saturating the motor. VM is the motor supply voltage, and RL is the motor winding resistance.

Equation 8. DRV8711 EQ5_IFSa_slva632.gif

TORQUE is a register used to scale the output. If TORQUE = 0xFF, then the SIN DAC is scaled by 1. As TORQUE is decreased, the reference is decreased as well.

As an example, the torque register can be reduced when the motor has been stopped. Reducing torque at this point could reduce the current required to hold the motor.

TORQUE Register Address = 0x01h
Bit Name Size R/W Default Description
7-0 TORQUE 8 R/W 0xFFh Sets full-scale output current for both H-bridges

ISGAIN controls the gain of the current sense amplifier. Note that from Equation 7, increasing this gain will decrease IFS since it is used in the feedback path.

CTRL Register Address = 0x00h
Bit Name Size R/W Default Description
9-8 ISGAIN 2 R/W 00 ISENSE amplifier gain set
00: Gain of 5
01: Gain of 10
10: Gain of 20
11: Gain of 40