100k
470pF
100k
470pF
OUT-
OUT+
Measurement and Analysis
11
SLOU435B – December 2015 – Revised February 2019
Copyright © 2015–2019, Texas Instruments Incorporated
DRV2624 ERM, LRA haptic driver evaluation kit
5
Measurement and Analysis
The DRV2624 uses PWM modulation to create the output signal for both ERM and LRA actuators. To
measure and observe the DRV2624 output waveform, connect an oscilloscope or other measurement
equipment to the filtered output test points,
OUT+
and
OUT–
.
Figure 14. Terminal Block and Test Points
The DRV2624 drives LRA and ERM actuators using a 20-kHz PWM modulated waveform, but only the
frequencies around the LRA resonant frequency or the ERM DC drive voltage are relevant to the haptic
actuator vibration. The higher frequency switching content does not contribute to the vibration strength of
the actuator and can make it difficult to interpret the modulated output waveform on an oscilloscope. The
oscilloscope image on the left shows the DRV2624 unfiltered waveform and the image on the right shows
a filtered version used for observation and measurement.
Figure 15. DRV2624 Unfiltered Waveform
Figure 16. DRV2624 Filtered Waveform