SLVSDN2E January   2018  – March 2021 DRV10974

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 Speed Input and Control
      2. 7.3.2 Motor Direction Change
      3. 7.3.3 Motor-Frequency Feedback (FG)
      4. 7.3.4 Lock Detection
        1. 7.3.4.1 Lock Kt Measure
        2. 7.3.4.2 Lock No Motor
        3. 7.3.4.3 Lock Open Loop Abnormal
        4. 7.3.4.4 Lock BEMF Abnormal
        5. 7.3.4.5 Lock Closed Loop Abnormal
        6. 7.3.4.6 Lock Speed Abnormal
      5. 7.3.5 Soft Current-Limit
      6. 7.3.6 Short-Circuit Current Protection
      7. 7.3.7 Overtemperature Protection
      8. 7.3.8 Undervoltage Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Spin-Up Settings
        1. 7.4.1.1 Motor Start
        2. 7.4.1.2 Initial Speed Detect
        3. 7.4.1.3 Align
      2. 7.4.2 Open-Loop Acceleration
      3. 7.4.3 Start-Up Current Sensing
      4. 7.4.4 Closed Loop
      5. 7.4.5 Control Advance Angle
  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
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.5 Soft Current-Limit

The current-limit function provides active protection for preventing damage as a result of high current. The soft current-limit does not use direct-current measurement for protection, but rather, uses the measured motor resistance (Rm) and motor velocity constant (Kt) to limit the voltage applied to the phase (U) such that the current does not exceed the limit value (I(LIMIT)). The soft current-limit scheme is shown in Figure 7-12 based on the calculation in Equation 4.

The soft current-limit is only active when in normal closed-loop mode and does not result in a fault condition nor does it result in the motor being stopped. The soft current-limit is typically useful for limiting the current that results from heavy loading during motor acceleration. The I(LIMIT) current is configured by an external resistor (R(CS)) as shown in Table 7-1.

GUID-6A952405-7053-459F-A6BB-915C9C510F0E-low.gifFigure 7-12 Current Limit

Use Equation 4 to calculate the I(LIMIT) value.

Equation 4. GUID-D6FADF68-5957-4402-BCEC-6B076EC2AE12-low.gif

Table 7-1 can be used to determine the I(LIMIT) value.

Table 7-1 Soft Current-Limit Selections
R(CS) [kΩ](1)I(LIMIT) [mA]
7.32200
16.2400
25.5600
38.3800
54.91000
80.61200
1151400
1821600 (1500 during align)
(1) All resistors are ±1 %.

Note:

The soft current-limit is not correct if the motor is out of phase with the commutation control logic (locked rotor). The soft current-limit is not effective under this condition.