Hi all, about L6229/L6235 which is the correct connection for the CBOOT capacitor? On the datasheet it is connected between VBOOT and VS, on the evaluation board it is connected between VBOOT and GND (see picture)

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Motor control hardware

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Cristiana SCARAMELBest answer

ST Employee

Hello @MBeda.1 and welcome to the ST Community.

We recommend the configuration with bootstrap capacitor (CBOOT) connected between VBOOT and Vs.

If it is connected to GND and Vs quickly drops, for example when a poorly load regulated supply sees a step change in current, the energy in CBOOT would go into the chip and possibly damage it.

On the other hand if CBOOT is connected to Vs and Vs drops, the entire charge pump circuitry drops so there would be no possibility of CBOOT energy going into the chip.

Another problem could be the noise on the GND, for example due to a bad layout, could cause an over-rating condition on bootstrap pin followed by the damaging of charge pump circuitry and device.

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