100k
470pF
100k
470pF
OUT
OUT- OUT+
From DRV2603
Measurement and Analysis
www.ti.com
Actuator Selection Resistor Configurations
Actuator Type R1 R2 R3 R34 R35
ERM Open Open 0Ω Open Open
LRA Open 0Ω Open Open 0Ω
External ERM Open Open 0Ω X
(1)
X
(1)
External LRA Open 0Ω Open X
(1)
X
(1)
(1)
Does not matter
4 Measurement and Analysis
4.1 Output Measurements
The DRV2603 uses PWM modulation to create the output signal for both ERM and LRA actuators. To
measure and observe the DRV2603 output waveform, connect an oscilloscope or other measurement
equipment to the filtered output test points, “OUT+” and “OUT-“.
Figure 12. Terminal Block and Test Points
The DRV2603 drives LRA and ERM actuators using a 20kHz 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 DRV2603 unfiltered waveform and the image on the right shows
a filtered version used for observation and measurement.
Figure 13. DRV2603 Unfiltered Waveform Figure 14. DRV2603 Filtered Waveform
To observe the modulated output waveform and ensure that the 20kHz switching waveform and
associated harmonics are not captured, use either a digital or analog, low pass filter when viewing the
output waveform. TI recommends using a 1st-order, low-pass filter with a cutoff between 1kHz and
3.5kHz.
Below are recommended output filters for use while measuring and characterizing the DRV2603. Certain
oscilloscopes have a built-in digital, low-pass filter, so no external components are required.
12
DRV2603 ERM/LRA Haptic Driver Evaluation Kit SLOU340A–May 2012–Revised May 2012
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