Datasheet BA6845FS Datasheet (ROHM)

Motor driver ICs

Stepping motor driver

BA6845FS

The BA6845FS is a stepping motor driver with a maximum output current of 1.0A. The logic input allows three output
modes : forward, reverse, and power save. The IC has a low output saturation voltage and is capable of driving motors
at low supply voltage.

Applications
Stepping motors for floppy disk drives

Features

1) Low output saturation voltage.

2) Power save circuit.

3) Thermal shutdown circuit.

Absolute maximum ratings (Ta = 25C)

Recommended operating conditions (Ta = 25C)

735

Motor driver ICs BA6845FS

Block diagram

736

Motor driver ICs BA6845FS

Pin descriptions

Input / output circuits (all resistances are typical values)

737

Motor driver ICs BA6845FS

Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V)

Truth table

738

Motor driver ICs BA6845FS

Application example

Operation notes

(1) Control logic pins
Do not apply voltage to control logic pins (pins 4, 5, 12,
and 13) when the V
voltage of each pin should be less than V

CC voltage is not applied to the IC. The

CC, if applied,

and should be more than the ground voltage.
(2) PCB arrangement
When changing the rotational direction of a motor, a large
current of up to a few hundred milliamperes can flow be­tween the motor power supply (pins 11 and 14) and
MGND (pins 1 and 8). Depending on the application, this
large output current may flow back to input pins, resulting
in output oscillation or other malfunctions. Make sure that
your design does not allow a common impedance be­tween the large current output lines and the input section.
Suppress the power supply impedance to low levels,
otherwise output oscillation may occur.

(3) Package power dissipation
The power dissipated by the IC varies widely with the
supply voltage and the output current. Give full consider­ation to the package power dissipation rating when set­ting the supply voltage and the output current.
(4) Ground pins
Pins 1, 3, 6, and 8 should have the lowest potential
(ground potential) in the IC.
(5) Thermal shutdown circuit
This circuit shuts down all the driver outputs when the
chip junction temperature is increased to about 175C
(typical). The thermal shutdown circuit is deactivated
when the temperature drops to about 20C (typical).
(6) Input pins (pins 4, 5, 12, and 13)
These pins have characteristics negatively correlated to
temperature. Give full consideration to the temperature
effect when using the IC.

739

Motor driver ICs BA6845FS

Electrical characteristic curves

740

External dimensions (Units: mm)