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DRV2700: extremely high ripple at boost voltage output

Part Number: DRV2700

Hello,

I have some troubles with noise ripple on the dc boost BST side of the DRV2700. Attached you find the layout and the schematics of the circuit.

I have programmed the dc boost voltage at 68,4V (rms) with the resistor voltage divider. In the screenshot from the oscilloscope measurement (osci_output.png) you can imagine, that on the boost dc voltage (BST pin) (yellow signal) is a ripple of Vpp=12,8V.

The magenta and the cyan signals are the out+ and out- signals (pins) . The differential voltage of the output signals is the piezo signal with Vpp=125V. Due to the differential measurement, the ripples are not present in the violet signal nevertheless, there is still some audible noise radiated by the piezo. I think there is anywhere a mistake in the circuit, because the ripple on the dc boost is extremely high.