Mixed technology programmable stepper motor driver

The authors describe a monolithic stepper motor driver designed mainly for computer peripheral applications. Realized in a mixed bipolar/CMOS/DMOS technologym it combines on the same chip four isolated 100 V 1.2 ohm DMOS transistors for motor phase rotation, an upper 0.6 ohm DMOS transistor for PWM control and CMOS and bipolar circuits for logic and signal processing. The IC is assembled in a 20-lead plastic DIL package and needs no external heatsink yet, thanks to the high efficiency of the DMOS power stage, it can drive a unipolar motor at 0.75 A/phase with supply voltages from 10 V to 40 V. Two devices can be used together to obtain 1.5 A/phase. Internal programmable logic simplifies or eliminates gate array design for direct microprocessor interfacing; the power on reset is self-generated and can also be activated externally. This component is fully protected against overheating, microprocessor output errors, and failures from the power section back to the logic microprocessor outputs