The new A3988 from Allegro Microsystems Europe is a quad DMOS full-bridge motor driver IC capable of driving up to two stepper motors or four dc motors.
Despite its very small package size, which requires less board space than typical single or dual H-Bridge devices, the new A3988 offers a high current rating, with each full-bridge output rated up to 1.2A and 36V.
It includes fixed off-time pulse width modulation (PWM) current regulators, along with two-bit nonlinear DACs (digital-to-analogue converters) that allow stepper motors to be controlled in full, half, and quarter steps, and dc motors in forward, reverse, and coast modes.
The PWM current regulator uses Allegro's patented mixed-decay mode for reduced audible motor noise, increased step accuracy, and reduced power dissipation. The use of synchronous rectification reduces power dissipation and can eliminate the need for expensive Schottky diodes, while the low-resistance DMOS outputs allow a higher average output current to be achieved because of the lower die temperature rise.
Protection features include thermal shutdown with hysteresis, undervoltage lockout and crossover current protection. Special power-up sequencing is not required.
The A3988 is supplied in a choice of two packages, designated EV and JP, with exposed power tabs for enhanced thermal performance. The EV is a 6 x 6mm, 36-pin QFN package with a nominal overall package height of 0.90mm. The JP is a 7 x 7mm 48-pin LQFP. Both packages are lead (Pb) free, with 100 per cent matt tin leadframe plating.
Target applications include office equipment such as printers and scanners, as well as a range of industrial applications from surveillance cameras to automated handling and test systems.
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