DRV8234: Practical voltage management

Tool/software:

My application requires that I may have to cope with between 12 and 20V input, but the motor I wish to control will usually be inexpensive 3-pole 12V '130'-size can motors, and I want to use speed control - and I would not expect the maximum speeds to require more than 12V for the loads being driven.

Does the DRV8234 manage the input voltage down in any other way than PWM duty cycle management?  (i.e. with 18 volt input might I expect the duty cycle to not exceed 66%)   Or: does the chip also step the voltage down internally when using speed control (as opposed to voltage control)?  I have studied the datasheet to the best of my comprehension, and I don't think it does.

The practical alternative is to use a buck convertor and manage VM to 12VDC before it is fed to the DRV8234...   but I want to reduce package space (/component count) to a minimum and I'd prefer not to have that extra regulator.

Practically, will I have issues with running nominally 12V motors with a higher VM?  The loads will not be high, and I can current manage in the DRV8234... it feels 'safe', but I thought I'd ask to confirm how the chip would function in this use case.

Mark.