ROHM BA6870S Datasheet

Motor driver ICs

3-phase motor driver

BA6870S

The BA6870S is a 3-phase, full-wave, pseudo-linear motor driver suited for VCR capstan motors. The IC has a torque
ripple cancellation circuit to reduce wow and flutter, and an output transistor saturation prevention circuit that provides
superb motor control over a wide range of current. The built-in motor power series regulator allows applications with low
power consumption.

Applications
3-phase VCR capstan motors

Features

1) 3-phase, full-wave, pseudo-linear driver system.

2) High performance torque ripple cancellation circuit.

3) Reversal braking by detecting the motor direction.

4) Saturation prevention circuit for high- and low-side
output transistors.

5) Motor power supply series regulators.

6) Built-in circuit for output-to-GND short-circuit detec­tion.

Absolute maximum ratings (Ta = 25C)

Recommended operating conditions (Ta = 25C)

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Motor driver ICs BA6870S

Block diagram

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Motor driver ICs BA6870S

Pin descriptions

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

Circuit operation

(1) Pseudo-linear output and torque ripple cancellation
The IC generates a trapezoidal (pseudo-linear) output
current, whose waveform phase is 30 degrees ahead of
that of the Hall input voltage (Fig. 1).

The trapezoidal waveform of output current would create
intermittence in the magnetic field generated by the
3-phase motor, and would result in an irregular rotation
of the motor. To prevent this, the output waveform is ob­tained by superimposing a triangular wave on the trape­zoidal wave (Fig. 2). This process is called torque ripple
cancellation.

CC1 = 5V, VM = VCC2 = 12V)

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