The MCF8315A offers four
methods of directly controlling the speed of the motor. The speed control method is
configured by SPEED_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 DIGITAL_SPEED_CTRL register
The speed can also be indirectly controlled by
varying the supply voltage (VM).
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 7-13.
Note:
- Analog, PWM and Frequency based speed input modes are available only when
MCF8315A is configured as a standby device (DEV_MODE = 0b).
- I2C based speed input mode is available in both sleep (DEV_MODE =
1b) and standby devices (DEV_MODE = 0b).
- TI recommends adding a 200-ms delay after device power-up or wake-up from
sleep mode before giving a speed command.
- If MAX_SPEED is set to 0, SPEED_REF is clamped
to zero (irrespective of DUTY_CMD) and motor is in stopped state.