A4985SESTR-T

The A4985 is a complete microstepping motor driver with
built-in translator for easy operation. It is designed to operate
bipolar stepper motors in full-, half-, quarter-, and eighth-step
modes. Step modes are selectable by MSx logic inputs. It has
an output drive capacity of up to 35 V and ±1 A. The A4985
includes a fixed off-time current regulator which has the ability
to operate in Slow or Mixed decay modes.
The ET package meets customer requirements for no smoke
no fire (NSNF) designs by adding no-connect pins between
critical output, sense, and supply pins. So, in the case of a
pin-to-adjacent-pin short, the device does not cause smoke
or fire. Additionally, the device does not cause smoke or fire
when any pin is shorted to ground or left open.
The translator is the key to the easy implementation of the
A4985. 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 A4985 interface is an ideal fit for applications where a
complex microprocessor is unavailable or is overburdened.
During stepping operation, the chopping control in the A4985
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
resultsin reduced audible motor noise, increased step accuracy,
and reduced power dissipation.