SLVSA11G October   2009  –  November 2015 DRV8828

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  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 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 Bridge Control
      3. 7.3.3 Current Regulation
      4. 7.3.4 Decay Mode
      5. 7.3.5 Blanking Time
      6. 7.3.6 Protection Circuits
        1. 7.3.6.1 Overcurrent Protection (OCP)
        2. 7.3.6.2 Thermal Shutdown (TSD)
        3. 7.3.6.3 Undervoltage Lockout (UVLO)
    4. 7.4 Device Functional Modes
      1. 7.4.1 nRESET and nSLEEP Operation
  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 Current Regulation
        2. 8.2.2.2 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
    3. 10.3 Power Dissipation
    4. 10.4 Heatsinking
      1. 10.4.1 Thermal Information
  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

Package Options

Mechanical Data (Package|Pins)
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 DRV8828 is used in brushed motor or stepper motor control. The onboard current regulation allows for limiting the motor current through simple pin configurations.

8.2 Typical Application

DRV8828 typ_app_slvsa11.gif Figure 7. Motor Control Circuitry

8.2.1 Design Requirements

For this design example, use the parameters listed in Table 3

Table 3. Design Parameters

PARAMETER REFERENCE VALUE
Supply Voltage VM 24 V
Motor Winding Resistance RM 3.9 Ohm
Motor Winding Inductance LM 2.9 mH
Target Chopping Current ITRIP 1.5 A
Sense Resistor RSENSE 200 mΩ
VREF Voltage VREF 1.5 V

8.2.2 Detailed Design Procedure

8.2.2.1 Current Regulation

The maximum current (ITRIP) is set by the Ix pins, the VREF analog voltage, and the sense resistor value (RSENSE). When starting a brushed DC motor, a large inrush current may occur because there is no back-EMF and high detent torque. Current regulation will act to limit this inrush current and prevent high current on start-up.

Equation 2. DRV8828 qu2_slvsa11.gif

Example - If the desired chopping current is 1.5 A:

  • Set RSENSE = 200 mΩ
  • VREF would have to be 1.5 V
  • Create a resistor divider network from V3P3OUT (3.3 V) to set VREF = 1.5 V
  • Set R2 = 10 kΩ and set R1 = 12 kΩ

8.2.2.2 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 x R. For example, if the RMS motor current is 1.5 A and a 200 mΩ sense resistor is used, the resistor will dissipate 1.5 A² × 0.2 Ω = 0.3 W. The power quickly increases with greater current levels.

Resistors typically have a rated power within some ambient temperature range, along with a de-rated 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

DRV8828 DRV8828_Current_Limiting.png Figure 8. DRV8828 Current Limiting
DRV8828 DRV8828_Direction_Change.png Figure 9. DRV8828 Direction Change