Unified, multi-mode step motor control IC and power multi-chip module exploit versatile, constant torque PWM operation and microstepping

This paper describes the pairing of a CMOS step motor control IC and an innovative power multichip module (PMCM) to realize versatile, low-cost PWM operation that integrates microstepping. This combination of circuitry simplifies the PWM operation of many two-phase, unipolar step motors; offers the essential benefits of fluid, quiet motor operation; and (essentially) eliminates step motor resonance issues. Additionally, the microstepping drive increases positional resolution (especially if mated to step motors produced for microstepping applications); achieves final positioning with less ringing and overshoot; and attains these outcomes with shorter elapsed times for the movements. This combination of a parallel-to-serial CMOS control IC with multi-chip module provides both digital and analog control of phase current ratios (8 logic levels of control plus linear regulation), and can continuously supply 1.2 A to both motor phase windings. This 1.2 A output rating equates to its maximum limitation (i.e. 100% in the ratio table), and 46 V is the motor supply restriction. PWM control is realized via separate 3-bit D/A converters and, further, linear regulation of the output current is achieved by varying the voltage level applied to each of two individual reference inputs. The CMOS controller IC accepts inputs from a microcontroller (or μP) and performs the parallel-to-serial conversion which provides the required serial data format for interfacing to the power multi-chip module. Five distinctive modes of motor control and operation are supported