SLVS855J July   2008  – March 2015 DRV8800 , DRV8801

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Feature Description
      1. 9.3.1  Logic Inputs
      2. 9.3.2  VREG (DRV8800 Only)
      3. 9.3.3  VPROPI (DRV8801 Only)
      4. 9.3.4  Charge Pump
      5. 9.3.5  Shutdown
      6. 9.3.6  Low-Power Mode
      7. 9.3.7  Braking
      8. 9.3.8  Diagnostic Output
      9. 9.3.9  Thermal Shutdown (TSD)
      10. 9.3.10 Overcurrent Protection
      11. 9.3.11 SENSE
    4. 9.4 Device Functional Modes
      1. 9.4.1 Device Operation
        1. 9.4.1.1 Slow-Decay SR (Brake Mode)
        2. 9.4.1.2 Fast Decay With Synchronous Rectification
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Motor Voltage
        2. 10.2.2.2 Power Dissipation
        3. 10.2.2.3 Motor Current Trip Point
        4. 10.2.2.4 Sense Resistor Selection
        5. 10.2.2.5 Drive Current
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
    1. 11.1 Bulk Capacitance
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Related Links
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10 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.

10.1 Application Information

DRV880x device is used in medium voltage brushed DC motor control applications.

10.2 Typical Application

DRV8800 DRV8801 typ_app_drv8800_slvs855.gifFigure 10. DRV8800 Typical Application Schematic
DRV8800 DRV8801 typ_app_drv8801_slvs855.gifFigure 11. DRV8801 Typical Application Schematic

10.2.1 Design Requirements

For this design example, use the parameters listed in Table 2 as the input parameters.

Table 2. Design Parameters

DESIGN PARAMETER REFERENCE EXAMPLE VALUE
Motor Voltage VBB 24 V
Motor RMS Current IRMS 0.8 A
Motor Startup Current ISTART 2 A
Motor Current Trip Point ITRIP 2.5 A

10.2.2 Detailed Design Procedure

10.2.2.1 Motor Voltage

The motor voltage to use will depend on the ratings of the motor selected and the desired RPM. A higher voltage spins a brushed DC motor faster with the same PWM duty cycle applied to the power FETs. A higher voltage also increases the rate of current change through the inductive motor windings.

10.2.2.2 Power Dissipation

The power dissipation of the DRV880x is a function of the RMS motor current and the each output’s FET resistance (RDS(ON)).

Equation 2. Power ≈ IRMS2 x (High-Side RDS(ON) + Low-Side RDS(ON))

For this example, the ambient temperature is 35°C, and the junction temperature reaches 65°C. At 65°C, the sum of RDS(ON) is about 1Ω. With an example motor current of 0.8A, the dissipated power in the form of heat will be 0.8 A2x 1 Ω = 0.64 W.

The temperature that the DRV880x reaches will depend on the thermal resistance to the air and PCB. It is important to solder the device PowerPAD to the PCB ground plane, with vias to the top and bottom board layers, to dissipate heat into the PCB and reduce the device temperature. In the example used here, the DRV880x had an effective thermal resistance RθJA of 47°C/W, and:

Equation 3. TJ = TA + (PD x RθJA) = 35°C + (0.64 W x 47°C/W) = 65°C

10.2.2.3 Motor Current Trip Point

When the voltage on pin SENSE exceeds VTRIP (0.5 V), overcurrent is detected. The RSENSE resistor should be sized to set the desired ITRIP level.

Equation 4. RSENSE = 0.5 V / ITRIP

To set ITRIP to 2.5 A, RSENSE = 0.5 V / 2.5 A = 0.2 Ω.

To prevent false trips, ITRIP must be higher than regular operating current. Motor current during startup is typically much higher than steady-state spinning, because the initial load torque is higher, and the absence of back-EMF causes a higher voltage and extra current across the motor windings.

It can be beneficial to limit startup current by using series inductors on the DRV880x output, as that allows ITRIP to be lower, and it may decrease the system’s required bulk capacitance. Startup current can also be limited by ramping the forward drive duty cycle.

10.2.2.4 Sense Resistor Selection

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

10.2.2.5 Drive Current

This current path is through the high-side sourcing DMOS driver, motor winding, and low-side sinking DMOS driver. Power dissipation I2R loses in one source and one sink DMOS driver, as shown in Equation 5.

Equation 5. DRV8800 DRV8801 equ1a_lvs855.gif

10.2.3 Application Curves

DRV8800 DRV8801 Fwd_fast_slrs063.png
Figure 12. Forward Drive, Fast Decay
DRV8800 DRV8801 Fwd_slow_slrs063.png
Figure 14. Forward Drive, Slow Decay
DRV8800 DRV8801 Rvs_fast_slrs063.png
Figure 13. Reverse Drive, Fast Decay
DRV8800 DRV8801 Rvs_slow_slrs063.png
Figure 15. Reverse Drive, Slow Decay