SLVSHO3 April   2024 DRV8235

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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 I2C Timing Requirements
    7. 6.7 Timing Diagrams
    8. 6.8 Typical Operating Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 External Components
      2. 7.3.2 Summary of Features
      3. 7.3.3 Bridge Control
      4. 7.3.4 Current Sense and Regulation (IPROPI)
        1. 7.3.4.1 Current Sensing
        2. 7.3.4.2 Current Regulation
          1. 7.3.4.2.1 Fixed Off-Time Current Regulation
          2. 7.3.4.2.2 Cycle-By-Cycle Current Regulation
      5. 7.3.5 Stall Detection
      6. 7.3.6 Motor Voltage and Speed Regulation
        1. 7.3.6.1 Internal Bridge Control
        2. 7.3.6.2 Setting Speed/Voltage Regulation Parameters
          1. 7.3.6.2.1 Speed and Voltage Set
          2. 7.3.6.2.2 Speed Scaling Factor
            1. 7.3.6.2.2.1 Target Speed Setting Example
          3. 7.3.6.2.3 Motor Resistance Inverse
          4. 7.3.6.2.4 Motor Resistance Inverse Scale
          5. 7.3.6.2.5 KMC Scaling Factor
          6. 7.3.6.2.6 KMC
          7. 7.3.6.2.7 VSNS_SEL
        3. 7.3.6.3 Soft-Start and Soft-Stop
          1. 7.3.6.3.1 TINRUSH
      7. 7.3.7 Protection Circuits
        1. 7.3.7.1 Overcurrent Protection (OCP)
        2. 7.3.7.2 Thermal Shutdown (TSD)
        3. 7.3.7.3 VM Undervoltage Lockout (VM UVLO)
        4. 7.3.7.4 Overvoltage Protection (OVP)
        5. 7.3.7.5 nFAULT Output
    4. 7.4 Device Functional Modes
      1. 7.4.1 Active Mode
      2. 7.4.2 Low-Power Sleep Mode
      3. 7.4.3 Fault Mode
    5. 7.5 Programming
      1. 7.5.1 I2C Communication
        1. 7.5.1.1 I2C Write
        2. 7.5.1.2 I2C Read
  9. 8 Register Map
    1. 8.1 DRV8235_STATUS Registers
    2. 8.2 DRV8235_CONFIG Registers
    3. 8.3 DRV8235_CTRL Registers
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application: Brushed DC Motor
      1. 9.2.1 Design Requirements
      2. 9.2.2 Stall Detection
        1. 9.2.2.1 Application Description
          1. 9.2.2.1.1 Stall Detection Timing
          2. 9.2.2.1.2 Hardware Stall Threshold Selection
      3. 9.2.3 Motor Speed and Voltage Regulation Application
        1. 9.2.3.1 Tuning Parameters
          1. 9.2.3.1.1 Resistance Parameters
          2. 9.2.3.1.2 KMC and KMC_SCALE
            1. 9.2.3.1.2.1 Case I
            2. 9.2.3.1.2.2 Case II
              1. 9.2.3.1.2.2.1 Method 1: Tuning from Scratch
                1. 9.2.3.1.2.2.1.1 Tuning KMC_SCALE
                2. 9.2.3.1.2.2.1.2 Tuning KMC
              2. 9.2.3.1.2.2.2 Method 2: Using the Proportionality factor
                1. 9.2.3.1.2.2.2.1 Working Example
      4. 9.2.4 Motor Voltage
      5. 9.2.5 Motor Current
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Bulk Capacitance
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

This section describes how to select INV_R and INV_R_SCALE. The first step is to find the motor resistance. This can be done in three ways:

  1. Use the motor resistance value mentioned in the data sheet of the motor. If this is not available, use one of the other methods listed below.
  2. Perform a voltage sweep at the motor terminals, stall the motor at each voltage level, and measure the motor current. Please note that at least 10 measurements are required at every voltage level whilst rotating the motor by approximately 30° for each measurement. This is because it is unknown if the commutator segments are in contact with the brushes in a particular motor position which renders a lower, incorrect motor resistance value. If motor resistance from the motor's data sheet is unavailable, then this method is recommended to obtain the value of motor resistance. Take the average of all values to calculate motor resistance.
  3. Measure the motor resistance using a digital multimeter. Please note that this process also needs to be done at every voltage level for 10 measurements each and then averaged out at the end for the same reason as mentioned above.

Note:

To perform a voltage sweep,

  1. Connect the motor directly to the power supply at a voltage just below where the motor starts to spin. As an example, set the power supply voltage to 1.5V for a 12V motor if the motor starts to spin at 1.7V.
  2. Read the current using a current probe, inline multimeter, or power supply readout.
  3. Calculate the motor resistance using the following equation: Motor Resistance = Voltage/Stall Current.
  4. Repeat this test across a range of voltages (ex. 1.3V, 1.4V, 1.5V, 1.6V) and find a consistent motor resistance value.

Once the motor resistance value is found, select an appropriate value of INV_R_SCALE and calculate INV_R. The formula to calculate INV_R is:

Equation 10. INV_R =1Motor Resistance×INV_R_SCALE

For example, if the motor resistance is 25Ω, we have the following possible results based on the choice of INV_R_SCALE:

Table 9-2 Selection Example for INV_R_SCALE and INV_R
Bit INV_R_SCALE value INV_R_SCALE/Motor Resistance

(Actual Value)

 Rounded Value

INV_R

 Comment
00b 2 2/25=0.08 0 Do not select, since output is 0.
01b 64 64/25=2.56 3 Avoid selecting, since low bit precision.
10b 1024 1024/25=40.96 41 Can select this value.
11b 8192 8192/25=327.68 328 Cannot select this value because 328 exceeds the maximum limit for INV_R (255).