Hi Judah,
Figure 18 in the DRV103 datasheet provides a linear valve driver circuit using a DAC to control the Duty Cycle Adjust pin. The duty cycle would be adjusted to produce a PWM train that has an average current value equal to the level required by the proportional selenoid for a particular opening, or closure. The duty cycle would have to be characterized and correlated to the range of current that the particular selonoid requires.
The linear valve application circuit doesn't include the Arduino microcontroller use and we haven't developed such circuitry for DRV103 control. That would have to be accomplished by the user.
Regards, Thomas
Precision Amplifiers Applications Engineering