DRV8426E: General understanding of current regulation

Tool/software:

Hi,

for my understanding the DRV8426E is regulating the current by turning on and of the voltage of the (stepper) motor. Or more precises, the voltage is switched on as long as the current hasn't reached V_Ref* K_v, this is followed by a decay period set by Toff and Decay parameter -> PWM voltage. Hence I would expect higher duty cycle with lower voltages and vice versa. Unfortunately I am lacking equipment to check the output current in detail, but I observe a significantly higher input current when increasing the voltage. I would expect more or less constant U*I

Can anybody explain where my thoughts are wrong, or what I am missing here?