SLOA188A October 2013 – November 2021 DRV2603 , DRV2604 , DRV2605 , DRV2605L-Q1 , DRV2624 , DRV2625
An LRA is a spring-mass system and thus must be driven at the resonance frequency to maximize efficiency. Similar to an electrical circuit at resonance, the LRA will reuse energy in the system when vibrating at resonance. Driving at a frequency a few hertz off resonance while trying to achieve the same performance as resonance operation will cause the mechanical spring force to oppose the magnetic force of the driver, resulting in wasted energy.
The DRV2605 or DRV2625 with auto-resonance detection can ensure that the actuator is driven efficiently. We measure efficiency using two metrics:
Output power for the 21 actuators in the previous section were measured and resulted in large efficiency improvements when driven by the DRV2605. Table 4-1 shows the percentage difference in efficiency for the 21 actuators. The improvement is a result of auto-resonance tracking. While measured with DRV2605, the DRV2604, DRV2624, and DRV2625 would be able to replicate similar results if not identical.
| No Auto-Resonance (Output ~230 Hz) | Auto-Resonance | Efficiency Improvement | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Power (mW) | Acceleration (Grms) | mW / G | Power (mW) | Acceleration (Grms) | mW / G | Acceleration Improvement | Power Improvement | Power / G Improvement | |
| 1 | 143.9 | 2.96 | 48.62 | 121.9 | 3.16 | 38.57 | 6.8% | 15.3% | 20.7% |
| 2 | 149.6 | 2.99 | 50.02 | 116.5 | 3.16 | 36.86 | 5.7% | 22.1% | 26.3% |
| 3 | 148.3 | 2.6 | 57.02 | 123.9 | 3.1 | 39.97 | 19.2% | 16.4% | 29.9% |
| 4 | 145.3 | 2.99 | 48.60 | 113.1 | 3.1 | 36.48 | 3.7% | 22.2% | 24.9% |
| 5 | 147.9 | 2.21 | 66.91 | 116.1 | 3.12 | 37.21 | 41.2% | 21.5% | 44.4% |
| 6 | 147.6 | 2.65 | 55.69 | 120.9 | 3.14 | 38.49 | 18.5% | 18.1% | 30.9% |
| 7 | 151.8 | 2.23 | 68.09 | 117.9 | 3.13 | 37.68 | 40.4% | 22.3% | 44.7% |
| 8 | 148.4 | 1.83 | 81.07 | 121.6 | 3.06 | 39.72 | 67.2% | 18.1% | 51.0% |
| 9 | 148.7 | 2.58 | 57.62 | 123.1 | 3.11 | 39.59 | 20.5% | 17.2% | 31.3% |
| 10 | 146.7 | 2.05 | 71.55 | 114.0 | 3.19 | 35.73 | 55.6% | 22.3% | 50.1% |
| 11 | 149.3 | 1.94 | 76.94 | 111.9 | 3.2 | 34.97 | 64.9% | 25.0% | 54.5% |
| 12 | 148.1 | 1.85 | 80.06 | 120.8 | 3.21 | 37.65 | 73.5% | 18.4% | 53.0% |
| 13 | 153.2 | 2.2 | 69.65 | 118.3 | 3.2 | 36.97 | 45.5% | 22.8% | 46.9% |
| 14 | 145.8 | 2.11 | 69.08 | 116.9 | 3.22 | 36.31 | 52.6% | 19.8% | 47.4% |
| 15 | 144.3 | 2.12 | 68.05 | 120.6 | 3.17 | 38.05 | 49.5% | 16.4% | 44.1% |
| 16 | 144.3 | 1.75 | 82.44 | 116.3 | 3.19 | 36.47 | 82.3% | 19.4% | 55.8% |
| 17 | 149.9 | 1.75 | 85.68 | 116.3 | 3.23 | 36.00 | 84.6% | 22.4% | 58.0% |
| 18 | 148.7 | 1.57 | 94.73 | 118.2 | 3.22 | 36.70 | 105.1% | 20.6% | 61.3% |
| 19 | 148.9 | 1.45 | 102.68 | 116.0 | 3.16 | 36.69 | 117.9% | 22.1% | 64.3% |
| 20 | 148.3 | 2.36 | 62.85 | 112.0 | 3.09 | 36.25 | 30.9% | 24.5% | 42.3% |
| 21 | 148.2 | 1.56 | 95.01 | 110.2 | 3.14 | 35.09 | 101.3% | 25.7% | 63.1% |
| AVG | 148.0 | 2.2 | 71.1 | 117.4 | 3.2 | 37.2 | 51.8% | 20.6% | 45.0% |