SLOA194A May   2014  – January 2022 DRV2603 , DRV2604 , DRV2604L , DRV2605 , DRV2605L , DRV2605L-Q1 , DRV2624 , DRV2625 , DRV2667

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Eccentric Rotating Mass
    2. 1.2 Linear Resonant Actuator
    3. 1.3 Piezo Actuator
  3. 2How to Measure Energy
    1. 2.1 Current Consumption
    2. 2.2 Energy Consumption
    3. 2.3 Current Versus Acceleration
  4. 3Energy Consumption Comparisons for ERM, LRA and Piezo
  5. 4Energy Consumption Advantage of DRV260x and DRV262x Drivers
  6. 5Appendix A Energy Consumption of Actuators
  7. 6Appendix B. Test Setup Picture
  8. 7Appendix C. Energy Consumption Calculation for Smartphone Scenarios
  9. 8Revision History

2.1 Current Consumption

This section compares the average current consumption of ERM, LRA, and Piezo. This is useful when comparing the instantaneous current consumption of each actuator. It can also show the maximum number of clicks for battery-powered products.

GUID-20211119-SS0I-FH1L-Z0TH-3K0TST4VVMC9-low.gif Figure 2-1 Click Current Consumption Measurements

Figure 2-1 shows the click waveforms of ERM, LRA, and Piezo actuators. The mean current measurement of the waveform shows the energy consumption of each type of actuator. Keeping peak acceleration constant around 0.9 g, the ERM consumes 124 mA, the LRA consumes 51.3 mA, and the Piezo consumes 62.6 mA.

For a 1200-mAh battery, we can use the current consumption to calculate the maximum number of clicks. Use the ERM values from Table 2-1 to calculate an example:

Table 2-1 Click Current Consumption Data
Click Mean Current (mA-per click) Time Window (ms) MAX Acceleration (g) MAX Number of Clicks (1200-mAh Battery)
ERM 124 50 0.868 696774
LRA 52.6 40 0.956 2053232
Piezo 62.6 19.61 0.921 3570076

Conclusion

  • Comparing ERM and LRA, the LRA consumes half the current of the ERM at the same acceleration.
  • The current consumption of a Piezo click is close to the consumption of an LRA click and is lower than the consumption of an ERM click.
  • For the Piezo, the maximum number of clicks is five times greater than the ERM. As for the LRA, the maximum number of clicks is three times greater than the ERM.