I am attempting to use a DRV8662 to amplify a square waveform from 6vpp to 30vpp. My input waveform is a very clean square wave at 25khz that goes from -3.3v to +3.3v. I want a louder sound, not a vibration, so I'm using a Piezo Speaker that resonates at 25khz and has a capacitance of 3600 pF.
I'm using the following circuit right off the data sheet with the following values:
L = 10mH
VBat = 3.3v
C1, C2, C3 = 0.1uf
C4, C5 = 1uf
R1 = 470 KOhm
R2 = 22 KOhm
R3 = 47 KOhm
Piezo Actuator = 3600 pF capacitance Piezo SPEAKER (Transducer)
DAC is producing a square wave at 25khz with 6.6vpp going from -3.3v to +3.3v
When I attempt to amplify the input square wave with the DRV8662, I end up with a very clean triangle waveform. It is 25khz at 30vpp going from -15v to +15v.
Unfortunately, this produces almost no volume as it doesn't maintain the voltage at the top or bottom of the waveform.
So, why did the waveform change shape from square input to triangle output?
Here's the input
Here's the output:
