The A3987 is a complete oneMicrostepping motor driver, with a built-in converter for easy operation. It operates bipolar stepper motors in full, 1/2, 1/4 and 1/16 step modes with output drive capacities of 50 volts and 1.5 amps. The A3987 includes a fixed downtime current regulator that operates in slow or mixed decay mode.
The converter is key to the A3987's ease of implementation. Simply enter a pulse into the "step" input to drive the motor to generate a microstep. There are no phase order tables, high-frequency control lines, or complex interfaces in this program. The A3987 interface is ideal for applications where complex microprocessors are unavailable or overloaded.
The A3987 chopper control automatically selects the current decay mode (slow or mixed). When a "step" signal appears, the converter determines whether that step will produce a higher or lower current in each motor phase. If the charge generates a higher current, set this decay mode to "slow" decay. If the charge produces a lower current, the decay mode is set to 30.1% of the "fast" attenuation. This current attenuation control scheme reduces audible motor noise, increases step accuracy, and reduces power dissipation.
Internal synchronous rectification control circuitry is used to improve power consumption during pulse-width modulation (PWM) operation.
Internal circuit protection includes thermal shutdown due to hysteresis, undervoltage lockout (UVLO), and crossover current protection. No special power-on sequencing is required.
The A3987 is available in an ultra-thin (1.2 mm, maximum height), 24-pin TSSOP (suffix LP) package with exposed thermal shield. Lead-free package with 100% matte tin leadframe plating.
- Low RDS(on)output
- Short-to-ground protection
- Load short-circuit protection
- Self-drive current attenuation mode detection/selection
- Mixed with slow current attenuation modes
- Synchronous rectification for low power dissipation
- Internal undervoltage lockout (UVLO) and thermal shutdown circuitry
- Crossover current protection