JAJSCW8A January   2017  – July 2018 DRV8886

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     概略回路図
  4. 4 改訂履歴
  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 Indexer Timing Requirements
    7. 6.7 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  Stepper Motor Driver Current Ratings
        1. 7.3.1.1 Peak Current Rating
        2. 7.3.1.2 rms Current Rating
        3. 7.3.1.3 Full-Scale Current Rating
      2. 7.3.2  PWM Motor Drivers
      3. 7.3.3  Microstepping Indexer
      4. 7.3.4  Current Regulation
      5. 7.3.5  Controlling RREF With an MCU DAC
      6. 7.3.6  Decay Modes
        1. 7.3.6.1 Mode 1: Slow Decay for Increasing Current, Mixed Decay for Decreasing Current
        2. 7.3.6.2 Mode 2: Mixed Decay for Increasing and Decreasing Current
        3. 7.3.6.3 Mode 3: Slow Decay for Increasing and Decreasing Current
      7. 7.3.7  Blanking Time
      8. 7.3.8  Charge Pump
      9. 7.3.9  Linear Voltage Regulators
      10. 7.3.10 Logic and Multi-Level Pin Diagrams
      11. 7.3.11 Protection Circuits
        1. 7.3.11.1 VM Undervoltage Lockout (UVLO)
        2. 7.3.11.2 VCP Undervoltage Lockout (CPUV)
        3. 7.3.11.3 Overcurrent Protection (OCP)
        4. 7.3.11.4 Thermal Shutdown (TSD)
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    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デバイスおよびドキュメントのサポート
    1. 11.1 ドキュメントのサポート
      1. 11.1.1 関連資料
    2. 11.2 ドキュメントの更新通知を受け取る方法
    3. 11.3 コミュニティ・リソース
    4. 11.4 商標
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 Glossary
  12. 12メカニカル、パッケージ、および注文情報

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

7.3.4 Current Regulation

The current through the motor windings is regulated by an adjustable, fixed-off-time PWM current-regulation circuit. When an H-bridge is enabled, current rises through the winding at a rate dependent on the supply 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 fixed 20 μs, period of time to decrease the current. After the off time expires, the bridge is re-enabled, starting another PWM cycle.

DRV8886 current_reg_lvsd39.gifFigure 14. Current Chopping Waveform

The PWM regulation current is set by a comparator which monitors the voltage across the current sense MOSFETs in parallel with the low-side power MOSFETs. The current sense MOSFETs are biased with a reference current that is the output of a current-mode sine-weighted DAC whose full-scale reference current is set by the current through the RREF pin. An external resistor is placed from the RREF pin to GND to set the reference current. In addition, the TRQ pin can further scale the reference current.

Use Equation 1 to calculate the full-scale regulation current.

Equation 1. DRV8886 eq_chop_current_lvsd39.gif

For example, if a 30-kΩ resistor is connected to the RREF pin, the full-scale regulation current is 1 A (TRQ at 100%).

The TRQ pin is the input to a DAC used to scale the output current. Table 5 lists the current scalar value for different inputs.

Table 5. Torque DAC Settings

TRQ CURRENT SCALAR (TRQ)
0 100%
Z 75%
1 50%