A CMOS integrated circuit for the closed-loop drive of step motors that avoids direct rotor position sensing is reported. The sequencer is integrated with the control circuit. The circuit has been fabricated on a 4 mu m gate array, and its operation with the motor and chopper drive is characterized. Dynamic torque-speed characteristics, which are linear up to 85% of the maximum static torque with a 40% increase in power output compared to open-loop operation, have been obtained from a test motor. The CMOS integrated circuit controller makes the use of a step motor a viable alternative to series DC motors. It can be extended to provide a closed-loop drive circuit for step-mode operation.
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