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DRV2603: Degradation and Leakage current

Akash S
Intellectual 800 points

Part Number: DRV2603

Hello,

I am using the DRV2603 in ERM mode to drive a 1020 vibration motor. We are seeing degradation on the EN pin leading to random leakage currents, possibly due to hard switching during motor ON/OFF. The motor takes a peak of 250mA.

To avoid this, we plan to use a soft start and soft stop using PWM. Could you please Recommend on the following:
1. Is there a recommended PWM ramp-up method for safely starting the motor?
2. During motor stop, should PWM be ramped down before disabling EN, or is setting PWM = 0 sufficient?
3. When turning the motor OFF, is any delay required between setting PWM = 0 and pulling EN low?

  • 0
    TI__Expert 6170 points
    It is highly unusual for the EN pin to experience degradation from motor switching, as it is a high-impedance logic input isolated from the power stage. However, the DRV2603 is an integrated H-bridge; if the inductive flyback or "kickback" from the motor exceeds the chip's internal protection limits, it can cause ground bounce or substrate injection, which may manifest as leakage on nearby logic pins like EN.
    Implementing a soft start/stop via the IN/PWM pin is an excellent way to reduce these inductive spikes and mechanical stress.
    1. Recommended PWM Ramp-Up Method 
    For a small 1020 ERM motor, the goal is to overcome static friction without creating a massive current inrush. 
    • Frequency: Ensure your PWM frequency is between 10 kHz and 250 kHz (the DRV2603 range). 20–30 kHz is usually the "sweet spot" to avoid audible whining while maintaining efficiency.
    • The Ramp: A linear ramp from 0% to your target duty cycle over 50ms to 100ms is typically sufficient for a 1020 motor.
    • Initial "Kick": Some motors have high stiction. You may need a "stiction break" where you jump immediately to 20% duty cycle, then ramp linearly to your target (e.g., 80% or 100%). 
    2. Motor Stop: Ramp Down vs. PWM = 0 
    Setting PWM = 0 immediately is essentially a "hard stop." Because the DRV2603 in ERM mode acts as an H-bridge, setting PWM to 0% (or 100% depending on your logic) typically puts the driver into a "Brake" state (shorting the motor windings together). 
    • Recommendation: Use a Ramp Down. Ramping from your running duty cycle to 0% over 50ms to 100ms allows the stored magnetic energy and mechanical momentum to dissipate gracefully.
    • Why: A sudden "Brake" (PWM = 0) causes a massive instantaneous current spike as the motor acts as a generator. Ramping down prevents the voltage on the supply rail VDD from spiking due to regenerative braking. 
    3. Delay between PWM = 0 and EN = Low 
    Yes, a delay is recommended to ensure the H-bridge has finished its transition and the motor's back-EMF has subsided. 
    • Required Delay: Minimum 1ms to 5ms.
    • Logic:
      1. Ramp PWM down to 0%.
      2. Wait 5ms (This ensures the internal logic and any residual inductive energy have stabilized).
      3. Set EN = Low to enter low-power shutdown.