8.4.3.1 ISD

The ISD function is used to identify the initial condition of the motor. If the function is disabled, the DRV10983 does not perform the initial speed detect function and treats the motor as if it is stationary.

Phase-to-phase comparators are used to detect the zero crossings of the BEMF voltage of the motor while it is coasting (motor phase outputs are in high-impedance state). Figure 13 shows the configuration of the comparators.

Figure 13. Initial Speed Detect Function

If the UW comparator output is lagging the UV comparator by 60°, the motor is spinning forward. If the UW comparator output is leading the UV comparator by 60°, the motor is spinning in reverse.

The motor speed is determined by measuring the time between two rising edges of either of the comparators.

If neither of the comparator outputs toggle for a given amount of time, the condition is defined as stationary. The amount of time can be programmed by setting the register bits ISDThr[1:0].