ZHCSB92G June   2013  – May 2017 DRV8711

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 修订历史记录
  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 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 Stepper Motor Speed
        2. 8.2.2.2 Current Regulation
        3. 8.2.2.3 Decay Modes
      3. 8.2.3 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. 11器件和文档支持
    1. 11.1 文档支持
      1. 11.1.1 相关文档
    2. 11.2 接收文档更新通知
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The DRV8711 is used in bipolar stepper control. The microstepping motor predriver provides additional precision and a smooth rotation from the stepper motor.

8.1.1 Sense Resistor

For optimal performance, it is important for the sense resistor to be:

  • Surface-mount
  • Low inductance
  • Rated for high enough power
  • Placed closely to the motor driver

The power dissipated by the sense resistor equals IRMS2 × R. For example, if peak motor current is 3 A, RMS motor current is 2 A, and a 0.05-Ω sense resistor is used, the resistor will dissipate 2 A2 × 0.05 Ω = 0.2 W. The power quickly increases with higher current levels.

Resistors typically have a rated power within some ambient temperature range, along with a derated power curve for high ambient temperatures. When a PCB is shared with other components generating heat, margin should be added. It is always best to measure the actual sense resistor temperature in a final system, along with the power MOSFETs, as those are often the hottest components.

Because power resistors are larger and more expensive than standard resistors, it is common practice to use multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat dissipation.

8.1.2 Optional Series Gate Resistor

In high current or high voltage applications, the low side predriver fault may assert due to noise in the system. In this application, TI recommends placing a 47 to 120-Ω resistor in series with the low side output and the gate of the low side FET. TI also recommends setting the dead time to 850 ns when adding a series resistor.

8.2 Typical Application

The following design is a common application of the DRV8711.

DRV8711 TypApplication_SLVSC40.gif Figure 20. Typical Application Schematic

8.2.1 Design Requirements

For this design example, use the parameters listed in Table 5 as the input parameters.

Table 5. Design Parameters

DESIGN PARAMETER REFERENCE EXAMPLE VALUE
Supply Voltage VM 24 V
Motor Winding Resistance RL 3.9 Ω
Motor Winding Inductance IL 2.9 mH
Motor Full Step Angle θstep 1.8°/step
Target Microstepping Level nm 8 µsteps per step
Target Motor Speed v 120 RPM
Target Full-Scale Current IFS 1.25 A

8.2.2 Detailed Design Procedure

8.2.2.1 Stepper Motor Speed

The first step in configuring the DRV8711 requires the desired motor speed and microstepping level. If the target application requires a constant speed, then a square wave with frequency ƒstep must be applied to the STEP pin.

If the target motor start-up speed is too high, the motor will not spin. Make sure that the motor can support the target speed or implement an acceleration profile to bring the motor up to speed.

For a desired motor speed (V), microstepping level (nm), and motor full step angle (θstep),

Equation 4. DRV8711 equation_01_slvsc40.gif
Equation 5. DRV8711 equation_02_slvsc40.gif

θstep can be found in the stepper motor data sheet or written on the motor itself.

For the DRV8711, the microstepping level is set by the MODE bits in the CTRL register. Higher microstepping will mean a smoother motor motion and less audible noise, but will increase switching losses and require a higher fstep to achieve the same motor speed.

8.2.2.2 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 6. 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).

8.2.2.3 Decay Modes

The DRV8711 supports three different decay modes: slow decay, fast decay, and mixed decay. The DRV8711 also supports automatic mixed decay mode, which minimizes current ripple. The current through the motor windings is regulated using programmable settings for blanking, decay and off time. This means that after any drive phase, when a motor winding current has hit the current chopping threshold (ITRIP), the DRV8711 will place the winding in the programmed decay modes until the cycle has expired. Afterward, a new drive phase starts.

The blanking time TBLANK defines the minimum drive time for the current chopping. ITRIP is ignored during TBLANK, so the winding current may overshoot the trip level.

8.2.3 Application Curves

DRV8711 DRV8711_32microsteps.png Figure 21. 1/32 Microstepping Drive Current
DRV8711 DRV8711_64microsteps.png Figure 22. 1/64 Microstepping Drive Current