SLVSDO1C January   2017  – March 2020 DRV8886AT

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    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 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
        1. 7.3.5.1 Various Sources of Error
          1. 7.3.5.1.1 VRREF, ARREF, and RREF Error
          2. 7.3.5.1.2 VDAC Error
        2. 7.3.5.2 Application-Specific Error Calculations
      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: Smart Tune Ripple Control
        4. 7.3.6.4 Mode 4: Smart Tune Dynamic Decay
      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. 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

7.3.5.2 Application-Specific Error Calculations

As described in the previous analysis, it is possible to obtain a tighter error calculations by using values for VRREF and ARREF for the specific application use case. The data sheet parameters represent limits based on design and characterization data across a wide range of temperatures and voltage with additional margin. For the following example, the operational voltage is limited to VVM = 24 V, a common operating point for the DRV8884, DRV8885, DRV8886, and DRV8886AT.

Considering this use case, Table 14 provides updated values for VRREF and ARREF.

Table 14. Values For DRV8885 VVM= 24-V

Parameter Minimum Typical Maximum
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200

Using values above and maintaining VDAC constant, the error percentage is reduced as shown in the following tables.

Table 15. IFS Error at 1 A, VDAC Fixed and Application Values

Parameter Minimum Typical Maximum
VDAC 0.4107 0.4107 0.4107
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 940.79 1000 1060.8
Error (%) –5.93 6.07

Table 16. IFS Error at 400 mA, VDAC Fixed and Application Values

Parameter Minimum Typical Maximum
VDAC 0.9035 0.9035 0.9035
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 358.54 400 443.18
Error (%) –10.4 10.75

Table 17. IFS Error at 200 mA, VDAC Fixed and Application Values

Parameter Minimum Typical Maximum
VDAC 1.0677 1.0677 1.0677
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 164.51 200 267.26
Error (%) –17.83 18.51

By keeping VDAC value fixed or close to be fixed, yields much less error variation. The same calculation can be made using a VDAC value with a ±3 % variation to compare error percentage difference as shown in the following tables.

Table 18. VDAC 3%, VRREF and ARREF for 24-V Application at 1 A

Parameter Minimum Typical Maximum
VDAC 0.3983 0.4107 0.4230
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 926.09 1000 1076.39
Error (%) –7.4 7.63

Table 19. VDAC 3%, VRREF and ARREF for 24-V Application at 400 mA

Parameter Minimum Typical Maximum
VDAC 0.8764 0.9035 0.9306
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 326.52 400 477.16
Error (%) –18.41 19.24

Table 20. VDAC 3%, VRREF and ARREF for 24-V Application at 200 mA

Parameter Minimum Typical Maximum
VDAC 1.0357 1.0677 1.0998
ARREF 28800 30000 31200
VRREF 1.207 1.232 1.257
RREF 19800 20000 20200
IFS (mA) 126.67 200 277.42
Error (%) –36.73 38.56

Table 18, Table 19, and Table 20 show values closer to the typical values for both VDAC, ARREF, and VRREF. From all these calculations, the error percentages for the 200 mA current are higher because at those very low values, the minimum change greatly affects the full current equation. One method to improve the low-value current accuracy is to use a combination of the MCU DAC and TRQ pin. This method can help improve the error by reducing the need to use only the DAC voltage to achieve the low full-scale current. An example of this method is to achieve 200 mA using the 400 mA DAC setting and the 50% TRQ setting.