SLVAG33 August   2026 DRV8904-Q1 , DRV8906-Q1 , DRV8908-Q1 , DRV8910-Q1 , DRV8912-Q1

 

  1.   1
  2.   Abstract
  3. 1Application Background
    1. 1.1 Device Overview
    2. 1.2 Overview of OLD Function
  4. 2OLD Application Issues and Analysis
    1. 2.1 Problem 1: OLD False Alarms Under Active Freewheeling with PWM Control
      1. 2.1.1 Problem Description
      2. 2.1.2 Cause Analysis
      3. 2.1.3 Application Recommendations
    2. 2.2 Problem 2: How to Maintain Output in the OLD State Through a Sleep-Wake Cycle
      1. 2.2.1 Problem Description
      2. 2.2.2 Cause Analysis
      3. 2.2.3 Waveform Verification
      4. 2.2.4 Application Recommendations
    3. 2.3 Problem 3: How LOLD (Low-Current Open-Load Detection) is Triggered
      1. 2.3.1 Problem Description
      2. 2.3.2 Cause Analysis
      3. 2.3.3 Waveform Verification
      4. 2.3.4 Application Recommendations
  5. 3Conclusion
  6. 4References

2.3.2 Cause Analysis

The root cause of the problem lies in the control hierarchy relationship between the two register bits HBx_OLD_DIS and HBx_LOLD_EN:

HBx_OLD_DIS = 1b completely disables all OLD detection functions for that half-bridge, including Active OLD, Negative-Current OLD, and Low-Current LOLD. This bit is the master switch for OLD and has the highest priority.

The scenario for HBx_LOLD_EN = 1b is: under the premise that OLD is globally enabled (HBx_OLD_DIS = 0b), the OLD threshold of the low-side FET of that half-bridge is switched to the low-current mode (IOLD_LOW), while simultaneously disabling OLD detection for the high-side FET to prevent the high-side FET from generating false alarms due to the excessively low IOLD_LOW threshold.

Therefore, when HBx_OLD_DIS = 1b, regardless of the value of HBx_LOLD_EN, the entire OLD function is turned off and LOLD cannot operate.

The complete OLD/LOLD control logic is shown in the table below:

Table 2-2 HBx_OLD_DIS / HBx_LOLD_EN Control Logic
HBx_OLD_DIS HBx_LOLD_EN LS FET OLD HS FET OLD OLD Threshold Fault Reporting
0b 0b Enabled Enabled IOLD (Active OLD) Enabled
0b 1b Enabled Disabled IOLD_LOW（LOLD） Enabled
1b / Disabled Disabled / Disabled[DW1]