The A3977xED and A3977xLP are complete microstepping motor drivers with built-in translator. They are designed to operate bipolar stepper motors in full-, half-, quarter-, and eighth-step modes, with output drive capability of 35 V and 2.5 A. The A3977 includes a fixed off-time current regulator that has the ability to operate in slow-, fast-, or mixed-decay modes. This currentdecay control scheme results in reduced audible motor noise, increased step accuracy, and reduced power dissipation. The translator is the key to the easy implementation of the A3977. By simply inputting one pulse on the STEP input the motor will take one step (full, half, quarter, or eighth depending on two logic inputs). There are no phase-sequence tables, high-frequency control lines, or complex interfaces to program. The A3977 interface is an ideal fit for applications where a complex P is unavailable or over-burdened. Internal synchronous-rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection includes thermal shutdown with hysteresis, under-voltage lockout (UVLO) and crossover-current protection. Special power-up sequencing is not required. The A3977 is supplied in a choice of two power packages, a 44-pin plastic PLCC with copper batwing tabs (suffix ED), and a thin (<1.2 mm), 28pin TSSOP with an exposed thermal pad (suffix LP). The SLP package is available in a lead-free version (100% matte tin leadframe).