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Reference

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The dummy filter shown in Figure 14 has the same settling time as the active filter; therefore, the offset is

cancelled and the issue is avoided.

Figure 15. Dummy Filter Waveform

3.5.2 Remove Filter for Analog Input

If the input signal is an analog waveform, as opposed to a PWM, then an input filter may not be

necessary. Before removing the filter, ensure that a simple RC filter is not needed to remove any artifacts

from the digital-to-analog converter (DAC) output or other input source. Follow these instructions to

remove the input filter completely.

1. Replace resistors R6, R7, R13, and R14 with 0-Ω resistors.

2. Remove resistors R17 and R18.

3. Remove capacitors C8, C9, C13, and C14. Do not remove ac coupling capacitors C4 and C5.

3.6 Output

The DRV8662 is capable of driving high-voltage piezo loads. When connecting a load, ensure that the

voltage rating of the piezo load is equal to or greater than the maximum output voltage set by the

feedback resistors.

3.6.1 Piezo Actuator Selection

There are several key specifications to consider when choosing a piezo actuator for haptics, including

size, blocking force, and displacement. However, the key electrical specifications are voltage rating and

capacitance. At the maximum frequency of 500 Hz, the DRV8662 is optimized to drive up to 50 nF at 200

, which is the highest voltage swing capability. It is also capable of driving larger capacitances if the

programmed boost voltage is lower or if the user limits the input to lower frequencies. (such as 300 Hz).

Table 7 gives a list of recommended piezo actuators.

Table 7. Piezo Actuator Selection

Voltage Rating

Manufacturer Part Number Capacitance (nF) (V

) Dimensions (mm)

AAC MLB3503-G 50 200 35 x 3 x 0.96

AAC MLB3503B-G 180 100 35 x 3 x 1

AAC MLB3503C-G 670 48 35 x 3 x 1

4 Reference

This section includes the DRV8662EVM schematic, PCB layout, and bill of materials.

DRV8662 Piezo Haptics Driver Evaluation Module SLOU319A–August 2011–Revised December 2012

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