MP6538 test board drive BLDC Current abnormal

Motor Drivers/Sensors
1

Title: MP6538 Evaluation Board Shows ~2A No-Load Current at 24V – Request for Review of Gate and Phase Waveforms

Hello MPS Team,

I am currently evaluating the MP6538 on a custom motor driver board and have encountered an issue with unexpectedly high no-load current consumption.

Test Conditions:

  • Supply voltage: 24V

  • PWM frequency: 25kHz

  • Duty cycle: up to 100%

  • BLDC motor running under no-load condition

Observed Results:

  • Our previous motor driver boards draw approximately 0.15A under no-load operation.

  • The MP6538-based board draws approximately 2A under the same no-load condition.

  • The motor already reaches its no-load speed at approximately 70% PWM duty cycle.

  • Increasing the duty cycle from 70% to 100% produces little additional speed increase, but the input current remains much higher than expected.

To investigate the issue, I measured the gate drive signals and phase-U voltage waveform.

Waveform Observations:

  1. High-side and low-side gate drive amplitudes are approximately 12V–13V.

  2. No obvious overlap between high-side and low-side gate signals is observed.

  3. The switching transitions appear generally clean, although some ringing is present during switching events.

  4. The phase-U voltage waveform shows expected PWM switching behavior.

  5. No obvious abnormal oscillation or gate-drive malfunction is visible from the captured waveforms.

I have attached:

My questions are:

  1. Is a no-load supply current of approximately 2A expected under these operating conditions?

  2. Do the attached gate-drive and phase-voltage waveforms indicate any abnormal behavior?

  3. Are there any known MP6538 configuration, layout, or gate-drive considerations that could result in significantly higher no-load current consumption?

  4. What additional measurements would you recommend to identify the source of the excess current?

If necessary, I can also provide:

  • Complete schematic

  • PCB layout

  • MOSFET part number

  • Additional oscilloscope captures

Any suggestions would be greatly appreciated.

Thank you.