The MCT8316A offers four methods of directly controlling the speed of the motor. The speed control method is configured by SPD_CTRL_MODE. The speed command can be controlled in one of the following four ways.

• PWM input on SPEED pin by varying duty cycle of input signal
• Frequency input on SPEED pin by varying frequency of input signal
• Analog input on SPEED pin by varying amplitude of input signal
• Over I²C by configuring SPEED_CTRL

The speed can also be indirectly controlled by varying the supply voltage (V_M).

The signal path from SPEED pin input (or I²C based speed input) to output duty cycle (DUTY OUT) applied to FETs is shown in Figure 8-14.

Figure 8-15 shows the relationship between DUTY CMD and SPEED REF / TARGET DUTY.

When speed loop is enabled, DUTY CMD sets the SPEED REF in Hz. MAX_SPEED sets the SPEED REF at DUTY CMD of 100%. MIN_DUTY sets the minimum SPEED REF (MIN_DUTY x MAX_SPEED). SPEED REF stays clamped at (MIN_DUTY x MAX_SPEED) for ZERO_DUTY_THR < DUTY CMD < MIN_DUTY.

When speed loop is disabled, DUTY CMD sets the TARGET DUTY in % - TARGET DUTY is 100% when DUTY CMD is 100% and TARGET DUTY is equal to MIN_DUTY when DUTY CMD is set to MIN_DUTY. TARGET DUTY stays clamped at MIN DUTY for ZERO_DUTY_THR < DUTY CMD < MIN_DUTY.

ZERO_DUTY_THR sets the DUTY CMD below which SPEED REF/ TARGET DUTY (speed loop enabled/disabled) is set to zero and motor is in stopped state. AVS, CL_ACC configure the transient characteristics of DUTY OUT; the steady state value of DUTY OUT is directly configured in % through TARGET DUTY (when speed loop is disabled) or through SPEED REF (when speed loop is enabled).