Vibration Motor
A haptic actuator creates a mechanical sensation. An eccentric rotating mass (ERM) produces vibration from rotation, while a linear resonant actuator (LRA) produces oscillatory movement. Their drive and calibration requirements differ.
An ERM actuator spins an eccentric mass; an LRA moves a mass back and forth around its mechanical resonance. The controller must match the actuator. TI's DRV2605L illustrates separate ERM and LRA modes, with resonance tracking for the LRA rather than one universal drive waveform.
In plain terms
A tiny DC motor with a deliberately off-balance weight on the shaft; spin it and the housing shakes.
Why designers use it
- Silent alerts on phones, smartwatches, and pagers.
- Tactile feedback on game controllers, VR controllers, and touchscreens.
- Wearable haptics for navigation cues without sound.
Best for
- Phone alerts
- Game controllers
- Wearables
Key specifications
- Actuator type: ERM or LRA (Use the corresponding driver mode and calibration)
- Drive limits: Actuator-specific (Do not substitute the driver's supply rating for the motor's rating)
- LRA driver example: DRV2605L: 125–300 Hz (The cited driver's recommended LRA frequency range, not an ERM rotation-speed rating)
- Mechanical mounting: Application-specific (Verify how the assembly transfers vibration)
When not to use it
- When the selected actuator and waveform cannot meet the required response, braking or repeatability.
- When acoustic noise or the mechanical mounting conflicts with the product requirements.
Common mistakes
- Assuming all haptic actuators use the same drive circuit. Verify the selected ERM or LRA and its driver settings.
- Adding or omitting external flyback components without checking the driver's actual output topology and recirculation requirements.
- Mounting the actuator so that the mechanical structure absorbs the intended tactile effect.
Where you will find it
- The DRV2605L supports a haptic effect library and control for ERM and LRA loads.
- Its application guidance includes actuator calibration and appropriate output connections. A driver must be configured for the actual actuator rather than chosen by a phone-brand analogy.
A short history
TI's DRV2605L datasheet documents distinct ERM and LRA control strategies. It is used here as a technical reference, not as evidence for which phone, pager or game controller first adopted a particular actuator.
Good to know
- TI's DRV2605L provides distinct control for ERM and LRA actuators, including automatic resonance tracking for LRA operation.
- The tactile result depends on the actuator, its mounting and its control waveform, not just a nominal frequency.