SLVSD18C June   2015  – August 2017 DRV8880

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified System Diagram
      2.      Microstepping Current Waveform
  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  Decay Modes
        1. 7.3.5.1 Mode 1: Slow Decay for Increasing and Decreasing Current
        2. 7.3.5.2 Mode 2: Slow Decay for Increasing Current, Mixed Decay for Decreasing current
        3. 7.3.5.3 Mode 3: Mixed Decay for Increasing and Decreasing Current
        4. 7.3.5.4 Mode 4: Slow Decay for Increasing Current, Fast Decay for Decreasing current
        5. 7.3.5.5 Mode 5: Fast Decay for Increasing and Decreasing Current
      6. 7.3.6  Smart Tune
      7. 7.3.7  Adaptive Blanking Time
      8. 7.3.8  Charge Pump
      9. 7.3.9  LDO Voltage Regulator
      10. 7.3.10 Logic and Tri-Level Pin Diagrams
      11. 7.3.11 Power Supplies and Input Pins
      12. 7.3.12 Protection Circuits
      13. 7.3.13 VM UVLO (UVLO2)
      14. 7.3.14 Logic Undervoltage (UVLO1)
      15. 7.3.15 VCP Undervoltage Lockout (CPUV)
      16. 7.3.16 Thermal Shutdown (TSD)
      17. 7.3.17 Overcurrent Protection (OCP)
    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
        4. 8.2.2.4 Sense Resistor
      3. 8.2.3 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 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

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RHR|28
  • PWP|28
Thermal pad, mechanical data (Package|Pins)
Orderable Information

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 DRV8880 is used in stepper control.

8.2 Typical Application

The following design procedure can be used to configure the DRV8880.

DRV8880 typ_app_lvsd18.gif Figure 28. Typical Application Schematic

8.2.1 Design Requirements

Table 12 gives design input parameters for system design.

Table 12. Design Parameters

DESIGN PARAMETER REFERENCE EXAMPLE VALUE
Supply voltage VM 24 V
Motor winding resistance RL 0.8 Ω/phase
Motor winding inductance LL 1.4 mH/phase
Motor full step angle θstep 1.8°/step
Target microstepping level nm 1/8 step
Target motor speed v 120 rpm
Target full-scale current IFS 1.5 A

8.2.2 Detailed Design Procedure

8.2.2.1 Stepper Motor Speed

The first step in configuring the DRV8880 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 speed is too high, the motor will not spin. Make sure that the motor can support the target speed.

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

Equation 2. DRV8880 eq_fstep_1_lvsd18.gif

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

For the DRV8880, the microstepping level is set by the Mx pins and can be any of the settings in the table below. Higher microstepping will mean a smother motor motion and less audible noise, but will increase switching losses and require a higher ƒstep to achieve the same motor speed.

Table 13. Microstepping Indexer Settings

M1 M0 STEP MODE
0 0 Full step (2-phase excitation) with 71% current
0 1 Non-circular 1/2 step
1 0 1/2 step
1 1 1/4 step
0 Z 1/8 step
1 Z 1/16 step

Example: Target 120 rpm at 1/8 microstep mode. The motor is 1.8°/step

Equation 3. DRV8880 eq_fstep_2_lvsd18.gif

8.2.2.2 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 VREF analog voltage, and the sense resistor value (RSENSE). During stepping, IFS defines the current chopping threshold (ITRIP) for the maximum current step.

Equation 4. DRV8880 eq_I_FS_1_lvsd18.gif

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

Table 14. 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 1.5 A
Set RSENSE = 100 mΩ, assume TRQ = 100%.
VREF would have to be 0.99 V.
Create a resistor divider from V3P3 (3.3 V) to set VREF ≈ 0.99 V.
Set R2 = 10 kΩ, set R1 = 22 kΩ

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

Equation 5. DRV8880 eq_I_FS_2_lvsd18.gif

8.2.2.3 Decay Modes

The DRV8880 supports several different decay modes: slow decay, fast decay, mixed decay, and AutoTune. The current through the motor windings is regulated using an adjustable fixed-time-off scheme. This means that after any drive phase, when a motor winding current has hit the current chopping threshold (ITRIP), the DRV8880 will place the winding in one of the decay modes for tOFF. After tOFF, a new drive phase starts. For fixed decay modes (slow, fast, and mixed), the best setting can be determined by operating the motor and choosing the best setting.

8.2.2.4 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 Irms 2 × R. For example, if the rms motor current is 1.4A and a 250 mΩ sense resistor is used, the resistor will dissipate 1.4 A2 × 0.25 Ω = 0.49 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.

8.2.3 Application Curves

DRV8880 app_01_lvsd18.gif
Figure 29. Mixed Decay 30% Fast on Increasing and Decreasing Steps
DRV8880 app_03_lvsd18.gif
Figure 31. Slow Decay on Increasing and Mixed Decay 30% Fast on Decreasing Steps
DRV8880 app_05_lvsd18.gif
Figure 33. Mixed Decay 30% Fast on Increasing and Decreasing Steps
DRV8880 app_02_lvsd18.gif
Figure 30. Slow Decay on Increasing and Decreasing Steps
DRV8880 app_04_lvsd18.gif
Figure 32. AutoTune
DRV8880 app_06_lvsd18.gif
Figure 34. AutoTune