10.4 Motor Control Guidelines

The DLPA100 motor control terminals should be filtered with voltage transient suppressing devices for improved startup reliability and noise immunity. Schottky diodes should be placed cathode to anode between VBB to motor terminals OUTA (pin 12), OUTB (pin 15), OUTC (pin 16) and CTAP (pin 13). Schottky diodes should also be placed cathode to anode between motor terminals OUTA (pin 12), OUTB (pin 15), OUTC (pin 16) and CTAP (pin 13) to ground. Series RC snubbers consisting of a capacitor (0.001 μF) in series with a resistor (150 Ω) should be placed between the motor terminals OUTA (pin12), OUTB (pin 15), and OUTC (pin 16) to CTAP (pin 13).

The value of the motor current sensing resistor on SENSE (pin 14) should be thoroughly evaluated for the application. Careful consideration should be taken in the amount of current draw during motor startup and braking with respect to the speed range and speed change timing requirements. It is recommended that the SENSE (pin 14) voltage does not exceed 450 mV. Most motors from today’s modern technology have relatively low operating currents but higher start-up currents which make it very difficult to achieve good signal to noise ratio during operating range and meet the 450 mV maximum on SENSE (pin 14). Most motors have demonstrated success well below 100 mV steady-state SENSE (pin 14) voltage. As long as good layout and component selection practices are followed, acceptable signal to noise ratios can be achieved at such low operating SENSE (pin 14) voltages. The typical SENSE resistor value ranges from 0.47 Ω to 2.2 Ω. A 1.0-Ω SENSE resistor value is suggested as a good starting point. Typically the steady-state SENSE (pin 14) voltage with a 1.0-Ω resistor will be near 100 mV.