LTC3786 overshoot with BLDC motor driver

Question

Circuit is as shown, very similar to the default boost converter. Input voltage is from a battery or DC supply, ranges from 10 to 19V, with 24V output. The scope images show the regulated 24V output on Ch1, and Ch2 is the ITH pin. The load is a BLDC motor that can change direction but is driven via a trapezoidal move profile. The spike is on a stop, just before a direction change. I might assume that the ITH is showing me the device is going to sleep, so the MOSFET devices are both OFF. Is this expected behavior? Is there a way to configure the 3786 to reduce the output voltage so that my peak ripple is significantly less?

ADIApproved · Accepted Answer

It looks like the motor is bumping the Vout up above the output set-point which would result in ITH pin pulling low (that would stop switching). The input voltage may also go up in this case since the current could flow from Vout to Vin. It may be helpful to look at the Vin and RUN pin levels as well.)

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LTC3786 overshoot with BLDC motor driver