SLVSD19A June   2015  – July 2015 DRV8881

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      DRV8881E Simplified System Diagram
      2.      DRV8881P Simplified System Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
    2.     DRV8881E PH/EN Pin Functions
    3.     DRV8881P PWM 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 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  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  Bridge Control
      4. 7.3.4  Current Regulation
      5. 7.3.5  Decay Modes
        1. 7.3.5.1 Mode 1: Slow Decay
        2. 7.3.5.2 Mode 2: Fast Decay
        3. 7.3.5.3 Mode 3: 30%/70% Mixed Decay
      6. 7.3.6  Smart tune
      7. 7.3.7  Adaptive Blanking Time
      8. 7.3.8  Parallel Mode
      9. 7.3.9  Charge Pump
      10. 7.3.10 LDO Voltage Regulator
      11. 7.3.11 Logic and Tri-Level Pin Diagrams
      12. 7.3.12 Protection Circuits
        1. 7.3.12.1 VM Undervoltage Lockout (UVLO)
        2. 7.3.12.2 VCP UVLO (CPUV)
        3. 7.3.12.3 Overcurrent Protection (OCP)
        4. 7.3.12.4 Thermal Shutdown (TSD)
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 DRV8881P Typical Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Current Regulation
          2. 8.2.1.2.2 Stepper Motor Speed
          3. 8.2.1.2.3 Decay Modes
          4. 8.2.1.2.4 Sense Resistor
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Alternate Application
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Current Regulation
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance Sizing
  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 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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

8.2.1.2.1 Current Regulation

In a stepper motor, the full-scale current (IFS) is the maximum current driven through either winding. This quantity will depend on the TRQ pins, the xVREF analog voltage, and the sense resistor value (RSENSE). AVREF and BVREF can be configured to drive different currents, but in this example the same full-scale current is used in both coils.

Equation 2. DRV8881 eq_I_FS_1_lvsd19.gif

TRQ is a DAC used to scale the output current. The current scalar value for different inputs is shown in Table 10.

Table 10. Torque DAC Settings

TRQ1 TRQ0 CURRENT SCALAR (TRQ)
1 1 25%
1 0 50%
0 1 75%
0 0 100%
Example: If the desired full-scale current is 800 mA
Set RSENSE = 250 mΩ, assume TRQ = 100%.
xVREF would have to be 1.32 V.
Create a resistor divider from V3P3 (3.3 V) to set AVREF and BVREF ≈ 1.32 V.
Set R2 = 10 kΩ, set R1 = 15 kΩ

Note that IFS must also follow Equation 3 in order to avoid saturating the motor. VM is the motor supply voltage, and RL is the motor winding resistance.

Equation 3. DRV8881 eq_I_FS_2_lvsd18.gif