Allegro – Dual full-bridge motor driver ICs with over-current protection (A4986)

Two new full-bridge stepper-motor driver ICs, the A4986 and A4987, have been added to the family of motor driver devices available from Allegro MicroSystems Europe.

The new devices are dual DMOS full-bridge stepper-motor drivers with parallel input communication and over-current protection, and offer improved micro-stepping accuracy along with high reliability.

Each device includes a fixed off-time pulse-width-modulation (PWM) current regulator, along with a 2-bit nonlinear digital-analogue converter that allows stepper motors to be controlled in full-, half- and quarter-step modes. Each full-bridge output of the A4986 and A4987 is rated at up to 35V and ±2A (A4986) or ±1A (A4987).

The PWM current regulator uses the Allegro patented mixed decay mode for reduced audible motor noise, increased step accuracy, and reduced power dissipation. Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation. Industry standard phase, I0 and I1 logic inputs are used to control each full-bridge, making it easy for the A4986 and A4987 to be used as replacements for most existing drivers.

The outputs are protected from short-circuits between the device and the load, across the load and between the load and ground, preventing thermal damage or flare-ups in the driver and associated circuitry. Other protection features include thermal shutdown with hysteresis, under-voltage lockout, crossover current and overcurrent protection. Special power-up sequencing is not required.

The Allegro A4986 and A4987 are offered in a 24-lead 7.8mm x 4.4mm x 1.2mm eTSSOP (LP) package. The A4987 is also available in a 24-contact 4mm x 4mm x 0.75mm QFN (ES) package. Both packages have exposed thermal pads for enhanced thermal dissipation, and are lead (PB) free with 100% matt tin-plated lead frames, says the company.