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Filtering and Adapting PWM Waveforms
21
SLOU403C – March 2015 – Revised June 2018
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DRV2700EVM High Voltage Piezo Driver Evaluation Kit
8
Filtering and Adapting PWM Waveforms
The DRV2700EVM has the capability to support many different input filter configurations. Depending on
the input mode, input frequency, and input voltage, the filter can be adapted to attenuate any undesired
out-of-band content. This section describes the input filter requirements and the various respective
configurations.
8.1
PWM Input
When using a high-frequency PWM input, a low-pass filter is required. The primary parameters for
determining the input filter are the PWM input frequency and sample rate. Because of the power ratings of
the DRV2700, the input filter has been designed to attenuate frequencies above 500 Hz. For samples
rates above 20 kHz, a simple first-order RC filter is recommended; however, for sample rates much lower
(such as 8 kHz), a first-order filter may not sufficiently attenuate the high-frequency content. Thus, for
lower sampling rates, a second order RC filter may be required. The following sections describe example
filter configurations for both first- and second-order filters. The DRV2700EVM default configuration uses a
second-order differential filter, but it can be replaced by a first-order, single-ended, or differential filter.
Figure 17. DRV2700EVM First- and Second-Order Filters
