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

7.3.4.2 Current Regulation

The DRV8235 integrates current regulation using either a fixed off-time or a cycle-by-cycle PWM current regulation scheme. This allows the device to limit the output current in case of a motor stall, high torque, or other high current load events autonomously. The current regulation scheme is selectable by the REG_CTRL bit in I2C.

The internal current regulation can be disabled by tying IPROPI to GND and setting the VREF pin voltage greater than GND if current feedback is not required. Additionally, current regulation can also be disabled by setting IMODE to 00b as explained below. If current feedback is required and current regulation is not required, set VVREF and RIPROPI such that VIPROPI never reaches the VVREF threshold. For proper operation of the current regulation circuit, VVREF must be within the range of the VREF pin voltage specified in the Recommended Operating Conditions table.

Table 7-6 REG_CTRL Functions
Bit*Current Regulation Mode
00bFixed Off-Time
01bCycle-By-Cycle
Note:

*Additional REG_CTRL options 10b and 11b allow selection between motor voltage or speed regulation described in Section 7.3.6.2.1.

The current regulation threshold (ITRIP) is set through a combination of the VREF voltage (VVREF) and IPROPI output resistor (RIPROPI). This is done by comparing the voltage drop across the external RIPROPI resistor to VVREF with an internal comparator.

Equation 3. ITRIP (A) x AIPROPI (μA/A) = VVREF (V) / RIPROPI (Ω)

For example, if VVREF = 3.3 V, RIPROPI = 1100 Ω and AIPROPI = 1500 μA/A, then ITRIP will be approximately 2 A.

VVREF must be lower than VVM by at least 1.25 V. The maximum recommended value of VVREF is 3.3 V. If INT_VREF bit is set to 1b, VVREF is internally selected with a fixed value of 3 V.

The ITRIP comparator has both a blanking time (tBLANK) and a deglitch time (tDEG). The internal blanking time helps to prevent voltage and current transients during output switching from affecting the current regulation. These transients may be caused by a capacitor inside the motor or motor terminals. The internal deglitch time ensures that transient conditions do not prematurely trigger the current regulation. In certain cases where the transient conditions are longer than the deglitch time, placing a 10-nF capacitor on the IPROPI pin, close to the device, helps filter the transients on IPROPI output so current regulation does not prematurely trigger. The capacitor value can be modified as needed, however large capacitor values may slow down the response time of the current regulation circuit.

The IMODE bits determine the behavior of current regulation for the motor driver.

  • When IMODE is 00b, current regulation is disabled.

  • When IMODE is 01b, the device performs current regulation only during the tINRUSH time when stall detection is enabled.

  • When IMODE is 10b, current regulation is enabled at all times.

The following table summarizes the IMODE bit settings.

Table 7-7 IMODE configuration
IMODE

EN_STALL

Description

00b

XNo current regulation at any time
01b

0b

Current regulation at all times

1b

Current regulation during tINRUSH only

1Xb

XCurrent regulation at all times