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

0

Ω

Open

Open

LRA

Open

0

Ω

Open

Open

0

Ω

External ERM

Open

Open

0

Ω

X

(1)

X

(1)

External LRA

Open

0

Ω

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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