The HR4985 is a complete microstepping motor driver withbuilt-in translator for easy operation. It is designed to operate bipolarstepper motors in full,1/2,1/4,and 1/8 step modes, with an output drive capacity of up to 35 V and ±1 A. The HR4985 includes a fixed off-time current regulator which has the ability to operate in Slow or Mixed decay modes.
The translator is the key to the easy implementation of the HR4988. Simply inputting one pulse on the STEP input drives the motor one microstep. There are no phase sequence tables, high frequency control lines, or
complex interfaces to program. The HR4985 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.
During stepping operation, the chopping control in the HR4985 automatically selects the current decay mode, Slow or Mixed. In Mixed decay mode, the device is set initially to a fast decay for a proportion of the fixed off-time, then to a slow decay for the remainder of the off-time. Mixed decay current control results in 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. Internal circuit protection includes: thermal shutdown with hysteresis, undervoltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.
The HR4985 is supplied in a surface mount QFN package (ES), 4mm × 4mm, with a nominal overall package height of 0.75 mm and an exposed pad for enhanced thermal dissipation. It is lead (Pb) free (suffix –T), with 100% matte tin plated leadframes.
Features and Benefits
Low RDS(ON) outputs
Automatic current decay mode detection/selection
Mixed and Slow current decay modes
Synchronous rectification for low power dissipation
Internal UVLO
Crossover-current protection
3.3 and 5 V compatible logic supply
Thermal shutdown circuitry
Short-to-ground protection
Shorted load protection
Four selectable step modes: full, 1/2, 1/4, 1/8
